Cataract Surgery : Introduction and Preparation [1 ed.] 9781617119941, 9781617116056

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Cataract Surgery Introduction and Preparation

Lucio Buratto • Stephen Brint • Laura Sacchi SLACK Incorporated

Lucio Buratto, MD Centro Ambrosiano Oftalmico Milan, Italy

Stephen F. Brint, MD, FACS Associate Clinical Professor of Ophthalmology Tulane University School of Medicine New Orleans, Louisiana

Laura Sacchi, MD Centro Ambrosiano Oftalmico Milan, Italy

www.Healio.com/books ISBN: 978-1-61711-605-6 Copyright © 2014 by SLACK Incorporated. Illustrations courtesy of Massimiliano Crespi and Lucio Burrato. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without written permission from the publisher, except for brief quotations embodied in critical articles and reviews. The procedures and practices described in this publication should be implemented in a manner consistent with the professional standards set for the circumstances that apply in each specific situation. Every effort has been made to confirm the accuracy of the information presented and to correctly relate generally accepted practices. The authors, editors, and publisher cannot accept responsibility for errors or exclusions or for the outcome of the material presented herein. There is no expressed or implied warranty of this book or information imparted by it. Care has been taken to ensure that drug selection and dosages are in accordance with currently accepted/ recommended practice. Off-label uses of drugs may be discussed. Due to continuing research, changes in government policy and regulations, and various effects of drug reactions and interactions, it is recommended that the reader carefully review all materials and literature provided for each drug, especially those that are new or not frequently used. Some drugs or devices in this publication have clearance for use in a restricted research setting by the Food and Drug and Administration or FDA. Each professional should determine the FDA status of any drug or device prior to use in their practice. Any review or mention of specific companies or products is not intended as an endorsement by the author or publisher. SLACK Incorporated uses a review process to evaluate submitted material. Prior to publication, educators or clinicians provide important feedback on the content that we publish. We welcome feedback on this work. Published by:

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Contact SLACK Incorporated for more information about other books in this field or about the availability of our books from distributors outside the United States. Library of Congress Cataloging-in-Publication Data Buratto, Lucio, author. Cataract surgery : introduction and preparation / Lucio Buratto, Stephen Brint, Laura Sacchi. p. ; cm. Includes bibliographical references and index. ISBN 978-1-61711-605-6 (hardback) I. Brint, Stephen F., 1946- author. II. Sacchi, Laura, author. III. Title. [DNLM: 1. Cataract Extraction--instrumentation. 2. Cataract Extraction--methods. WW 260] RE451 617.7’42059--dc23 2013042273 For permission to reprint material in another publication, contact SLACK Incorporated. Authorization to photocopy items for internal, personal, or academic use is granted by SLACK Incorporated provided that the appropriate fee is paid directly to Copyright Clearance Center. Prior to photocopying items, please contact the Copyright Clearance Center at 222 Rosewood Drive, Danvers, MA 01923 USA; phone: 978-7507

DEDICATION To Bruno Monfrini, the person who allowed me to discover phacoemulsification. Lucio Buratto, MD

I have been so fortunate to have great teachers and friends who have helped me through the management of the inevitable complications of cataract surgery and have made me a better surgeon. Stephen F. Brint, MD, FACS

To Anna, whose infectious happiness transforms every moment into a memorable event. Laura Sacchi, MD

CONTENTS Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix About the Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Contributing Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Foreword by Vittorio Picardo, MD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii .

Part I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chapter 1

Microscopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 2

Surgical Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 3

Patient Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 4

Eye Examination and Presurgery Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 5

Hardness of the Nucleus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 6

The Pupil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 7

Anesthesia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 8

Preparation of the Patient and the Operating Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 9

Incisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Chapter 10 Viscoelastic Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Chapter 11 Capsulorrhexis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Chapter 12 Hydrodissection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Chapter 13 Intraocular Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Chapter 14 Refractive Cataract Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Chapter 15 Prevention of Endophthalmitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD

Contents  viii

Part II. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Chapter 16 Ophthalmic Viscosurgical Devices for Modern Cataract Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Steve A. Arshinoff, MD, FRCSC Chapter 17 Cataract Surgery Incisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Daniel Calladine, BMedSci, BMBS, FRCOphth Recommended Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Financial Disclosures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

ACKNOWLEDGMENTS The publication of a book is an extremely difficult and exhausting procedure; it involves an incredible amount of work. The completion of such an enterprise would not have been possible without the smooth-running organization and the assistance of my reliable team of collaborators. I would like to thank a number of them personally: Domenico Boccuzzi, Luigi Caretti, Mario Romano, Laura Sacchi, and Rosalia Sorce for their invaluable contribution to the production of this series of books on cataract surgery. Heartfelt thanks also to Massimiliano Crespi, the artist who produced the magnificent drawings, particularly for his unique ability to transfer the author’s thoughts and ideas onto paper; my warmest thanks also to Salvatore Ferrandes who was in charge of the iconographic and clinical aspects of the publications. I would like to thank the staff of Medicongress, in particular Monica Gingardi, for their excellent organizational and operational skills. Sincere thanks to my dear friend Vittorio Picardo for his revision of the final version of the text. Thanks are also due to SLACK Incorporated, my American publisher of the English versions, for their first-class work in promoting the international distribution of the publications. Last but not least, I would like to thank my dear friend and superb coauthor Steve Brint for his invaluable contribution. Lucio Buratto, MD

ABOUT THE AUTHORS Lucio Buratto, MD is a cataract surgeon by choice. Throughout his professional career, he has been recognized with countless international awards and commendations for the important and highly innovative contributions he has made in the field of ophthalmology. He was the first surgeon in the world to use the bimanual irrigation/aspiration system. He began using phacoemulsification in 1978 and started implanting the artificial crystalline lens in the posterior chamber in 1979. In Milan, in 1980, he organized a conference called “New methods of cataract extraction and the intraocular insertion of corrective lenses”; this event included live surgery sessions and set the foundation for the series of videocataract conferences. In 1982, he presented the YAG laser to his Italian colleagues, and in 1992, he introduced the new technique of sutureless cataract surgery. In 1987, he published his first book on modern cataract surgery in Italian. For many years, this book was considered to be the “Italian Bible” of cataract surgery. In 1995, he published an English version of the book Phacoemulsification: Principles and Techniques. He has published a total of 24 books on cataract surgery in many different languages. In the period between December 1997 and December 2005, he was President of AICCER (the Italian Association of Cataract and Refractive Surgery).

Stephen F. Brint, MD, FACS was the first physician in the United States to perform the LASIK procedure in June 1991, after working with Dr. Lucio Buratto in Milan to perfect the technique. He was the medical monitor of the first US FDA LASIK study and has been a lead investigator for both the Alcon Custom Cornea LASIK procedure as well as the Medical Monitor for all of the US FDA Wavelight Allegretto Wavefront Optimized and Custom Studies. He graduated from Tulane University School of Medicine, New Orleans, Louisiana, and completed his residency there as well in 1977, continuing to serve as Associate Clinical Professor of Ophthalmology. In addition to his vast LASIK experience of over 30,000 LASIK procedures, many with the Intralase All Laser LASIK technique, he is a renowned cataract/lens surgeon, having participated in the FDA clinical trials of the new intraocular lenses, including ReSTOR and ReZoom, and toric IOLs. He is board-certified by the American Board of Ophthalmology and a Fellow of the American College of Surgeons. He has been recognized as “The Best Doctor in New Orleans” by New Orleans Magazine for the past 10 years and has been selected by his peers for the 2000–2012 editions of The Best Doctors in America. Dr. Brint is a leading cataract surgeon and instructor, and the author of the 3 definitive textbooks on LASIK and cataract surgery, including the most recent Custom LASIK. Dr. Brint performs surgery and delivers lectures around the world, including Europe, Russia, China, Japan, Australia, Singapore, Africa, and South America. Dr. Brint has a passion for education and research, and most recently, he has been involved with the refinement of the intraoperative aberrometer for selecting IOL power and femtosecond laser-assisted cataract surgery.

Laura Sacchi, MD graduated in medicine and specialized in ophthalmology at the University of Milan. She was Chief Consultant at Milan’s San Giuseppe Hospital and at Crema’s Ospedale Maggiore. She has lectured at a number of national and international conferences. She has worked with Dr. Buratto for approximately 10 years, and at present, she is a private consultant at his clinic, Centro Ambrosiano Oftalmico. Her areas of expertise include refractive surgery, cataract surgery, the diagnosis and treatment of keratoconus, retinal pathologies, and pediatric ophthalmology.

CONTRIBUTING AUTHORS Steve A. Arshinoff, MD, FRCSC Private Practice Humber River Hospital Toronto, Canada Medical Director Mobile Medical Eye Care Unit Canadian National Institute for the Blind Ontario Medical Association Ontario, Canada

Daniel Calladine, BMedSci BMBS FRCOphth Consultant Ophthalmologist Worcestershire Acute Hospitals NHS Trust United Kingdom

FOREWORD Cataract surgery, performed using phacoemulsification, with the ever-increasing popularity of the femtolaser, requires meticulous preparation by the surgeon; the surgeon must be familiar with the sequence of steps of the surgery and the correct organization of the procedure. Dr. Lucio Buratto is a surgeon who has enormous experience in surgery of the anterior segment; many years after his previous publication on this subject, he decided to publish a comprehensive collection of volumes on cataract surgery; in this book, one of the five in the series, he examines the most popular instruments used, the pre-operative examination, and the operating technique. The numerous congresses that Dr. Buratto has organized over the years have provided the participating delegates with the very latest, updated information, leaving them ready to approach cataract surgery for their patients in the best way possible; these were the guidelines of this first book in the new series on cataract surgery. Dr. Buratto assisted by Dr. Sacchi, who has worked with him for many years, wishes to lead the young surgeons by the hand and guide them along this exciting pathway of professional training and specialist information; the surgeons will gain more experience with phacoemulsification and the femtolaser, and learn all of the details, even the very smallest, associated with the procedure. Dr. Buratto starts from an important principle—that a cataract procedure cannot be performed without the surgeon being fully aware of the characteristics of the equipment and devices used; it cannot be successful if the patient has not been examined correctly and completely; and it cannot be an option if the surgeon is not aware of the risks associated with incorrect surgical maneuvers. Reading and understanding the contents of this book will allow the surgeon to enter the operating room confidently with these concepts clear in his mind; he will have absorbed all of the advice and will be fully aware that cataract surgery is now a sophisticated technique of visual rehabilitation associated with the patients’ increasing high expectations for perfect results. Vittorio Picardo, MD Head Ophthalmological Department Casa di Cura “Nuova Itor” Rome, Italy

INTRODUCTION The decision to perform cataract surgery has always depended on the opacity of the crystalline lens (established by an ophthalmologist) and on the patient’s visual acuity, measured during an eye exam. In the past, when cataract surgery was performed with intracapsular or extracapsular techniques, patients underwent surgery when the level of lens opacity was severe (white or black cataract) and with levels of visual acuity below 1–2/10. Naturally, the patients’ quality of life was seriously affected and their visual conditions were very debilitating. Surgical techniques at the time were very aggressive and a decent surgical result was obtained only if the operation was performed on eyes with advanced cataracts. Techniques were not very refined and large incisions were required for the total extrusion of the crystalline lens. Optical rehabilitation was limited because of high levels of secondary astigmatism, large incisions and many sutures, as well as iatrogenic trauma in the cornea and iris tissue. Surgical aphakia was corrected only with 12-diopter spectacles, which were very heavy and quite uncomfortable. The resulting poor quality of life was a good reason to undergo surgery only when the opacity was significant. The introduction of artificial lenses and phacoemulsification (and their continuous improvement) has, in time, changed the timing at which patients are referred for surgery. The reasons included the availability of artificial lenses that could correct surgical aphakia and the high hyperopia induced by the removal of the crystalline lens, as well as less invasive surgery techniques. Even so, complications were still likely, particularly at the beginning, when the first operations performed with phacoemulsification sometimes caused a considerable loss of endothelial cells, which often made corneal transplantation necessary. Rupture of the posterior capsule (with loss of material into the vitreous chamber followed by vitrectomy) was not infrequent, nor was the loss of vitreous in the anterior chamber, which led to secondary deformation of the pupil and cystoid macular edema, and in some cases vitreoretinal traction in the months following surgery. Furthermore, surgeons performing cataract surgery with ultrasound phacoemulsification obtained results that were good, but not excellent, for a number of reasons, for example, the lack of viscoelastic substances, unreliable phacoemulsification machines, and operating on hard cataracts. The last factor was closely related to not infrequent postoperative complications and with the lessthan-excellent results in terms of vision. A vicious cycle was thus established—the fear of frequent complications (and the associated medical and legal implications) induced surgeons to operate late and, in any case, to select patients carefully. Only later—when results gradually improved—surgery was also offered to younger patients whose visual acuity was 4/10 or worse and who had less advanced cataracts. Even in these cases, although these patients had decent vision, their quality of life was seriously affected, because sometimes reading a newspaper or a book required a lot of concentration, and dazzling lights and distortion of light sources at twilight (or in full day time) made driving difficult. Phacoemulsification improved with the introduction of capsulorrhexis and the fragmentation of the cataract nucleus with specific spatulas and choppers. The use of more precise machines and better training in surgical techniques for surgeons led to a reduction in severity and incidence of postoperative complications associated with the technique. Although surgical aphakia was corrected with the introduction of the first rigid, artificial crystalline lenses, these devices were still not able to ensure a good result in terms of vision because of high astigmatism caused by large surgical incisions and large number of sutures. This was true even if improved centration of the lenses in the capsular bag ensured a better vision result compared with the past. The development of soft or foldable artificial lenses has, without doubt, been a very important turning point in the history of cataract surgery. From this point, the prospects for surgeons and patients changed because, as the technology of these lenses and of surgical procedures advanced, increasingly smaller incisions were permitted, which meant that sutures were no longer necessary and that postoperative astigmatism was significantly reduced. Cataract surgery was no longer surgery performed to cure a disease (dense cataracts meant blindness)—it had became a vehicle to improve vision, so ophthalmologists began offering cataract surgery to a different class of patients, where quality of vision and life became increasingly important when deciding to operate. While artificial lenses were being introduced, instruments that could accurately calculate the power of the artificial lenses were developed. Biometric scanners and ultrasound scanners became more and more accurate and better performing and the first automatic systems were introduced (IOLMaster). All the above meant that surgery was safer and less and less invasive. With this intent, microincision surgery was born—cataracts could be removed through smaller and smaller incisions (1.6 to 2.0 mm) that had virtually no effect on corneal sphericity. During the period between the birth of ICCE and phaco MICS, while surgery techniques became increasingly accurate, patient anesthesia became less complicated. General anesthesia was required at first, which was risky in elderly patients with health problems. It was then replaced by retrobulbar block (which could damage the eye). Gradually, this kind of anesthesia was replaced by peribulbar and parabulbar blocks, which are less risky for the health of patients and for the

xviii  Introduction eye undergoing surgery. The most recent kind of anesthesia is topical anesthesia with eye drops, which has considerably reduced complications related to anesthesia and all the associated medical and legal implications. The kind of anesthesia required for surgery has also modified surgical times and reduced (and then removed) the need to admit patients into hospital, which meant that cataract surgery became a day-hospital procedure and eventually an out-patient operation. The development of high-definition instruments to study the retina (optical coherence tomography) has, without doubt, contributed to making surgeons more willing to perform cataract surgery at earlier stages because of the improved knowledge of the functional recovery prognosis (which is closely related to the clinical conditions of the patient’s macular region). Today, safer surgical techniques, reduced surgical and recovery times, and the availability of highly performing artificial crystalline lenses (aspheric, multifocal, accommodative, and toric lenses) have significantly changed the desire for cataract surgery. More and more often surgery is requested by patients and not necessarily recommended by ophthalmologists. Surgeons are frequently asked to operate on very early cataracts, when visual acuity is still good (8–10/10). There are also more and more patients who ask for surgery to correct preexisting refractive errors, which are not adequately solved through the use of contact lenses or glasses. This also depends on “aging.” The life of patients who are 65 to 70 years old today is very different from the lives of our grandparents and great-grandparents. They are more active and live more dynamically than did people that age 20 to 30 years ago. They often drive fast, powerful cars and are still actively employed. They use the most recent technological gadgets on a daily basis and these devices usually require good visual acuity and quality. Technological instruments such as mobile phones, iPads, laptops, netbooks, and GPS (which are becoming more and more popular) require good vision, not just in terms of visual acuity, but visual quality as well, if they are to be easy and comfortable to use. The lack of contrast sensitivity or brightness perception or images and light sources appearing distorted in poor light conditions make the use of these technological instruments difficult, which can, in part, explain why a large number of people request early surgery. It is clear how, today, we find ourselves in situations in which visual performance must be excellent—3D cinema and high-definition television are two examples. To be able to appreciate these technologies, good contrast sensitivity and good brightness perception are needed, possibly without aberrations. When should surgery be performed? That is the question. It is clear that cases of good visual acuity do not always translate to good-quality vision. Just think about a patient with high refractive myopia, in which a peripheral cortical opacity develops in the crystalline lens. He or she will have limited vision quality, especially in conditions of poor light (eg, driving at night). On the other hand, a patient with hyperopia with the beginnings of nuclear sclerosis will complain of distance vision gradually worsening and of being uncomfortable when reading, which causes eye fatigue. The decision to operate these patients in the early stages is completely justified, partly because today the surgical technique is quite safe and accurate and the latest-generation artificial lenses are available. These lenses do not just correct the high secondary hyperopia caused by surgical aphakia; they can also improve patient distant and near vision (multifocal and accommodative lenses). Finally, the use of femtosecond lasers in cataract surgery is the last frontier of safer, more precise surgery that is highly reproducible and standardized. It offers surgeons the chance to center the capsulorrhexis perfectly, which leads to optimal positioning of the artificial lens, and the precise location of corneal incisions (for access to the anterior chamber) and arcuate incisions (for correction of preexisting astigmatisms). The fragmentation of the nucleus reduces manipulation procedures and the amount of ultrasound used during cataract removal. Long-term management is one of the unknown factors in all this, that is, what are the problems and risks that these patients face in the future? Reduced surgical time and trauma ensure a reduction in intra- and postoperative complications, but they cannot predict what other effects there will be on other eye tissues over time. There is no way of knowing, for example, if surgery performed early increases the risk of degenerative diseases of the macula and retinal periphery. Lucio Buratto, MD

Part I

1 Microscopes Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD A microscope can generally be described as an instrument that magnifies images. In ophthalmology, a surgical microscope provides magnification of the operating field, with a sufficiently long focus for direct observation of surgery. It may have an autofocus device, be designed to have an assistant’s scope, and have a beam splitter for a video camera. Magnification is the apparent size of an object. The smaller the distance between the object and the eye of the observer, the larger the object’s image. The shortest distance for a young, emmetropic human eye to have clear vision is 250 mm, so a refractive medium (converging magnifying lens) is required between the object and the eye to obtain enlarged images. The lens deviates the divergent light rays coming from the object and converges them onto the retina at a distance below the minimal focal distance, which is conventionally established to be 250 mm (Figure 1-1). In a simple microscope, there is only one lens, so a compound microscope is needed to obtain greater magnification. This kind of microscope has two lens systems: the objective and the ocular. The objective creates a real image of the object. The image size depends on the distance between the object and the objective. The image is further magnified by the ocular lens (Figure 1-2). To change the total magnification capacity of a compound microscope, the objective and/or the ocular must be replaced, so a compound microscope with variable magnification must have a third system of lenses, the variable group, between the ocular and the objective lens systems. This makes a surgical microscope more flexible to use because the objective establishes the working distance, the ocular (or better still, the binocular) determines the base magnifying power, and, finally, the variable group is used

to choose the most appropriate magnification. However, it is important to remember that by increasing image magnification, the depth and size of the field of view are reduced. The components of a surgical microscope are as follows: The objective, whose total length determines the distance between the microscope (and therefore the surgeon) and the operating field. ●

●

●

●

●

The binocular complex, which is made up of a system of lenses that determines magnification and by the prisms that deviate light rays to make them parallel. The oculars, which is a lens system that determines the microscope’s highest magnifying power and can be replaced. Every ocular has a scale to correct the surgeon’s refractive error. The eyepieces, which can be vertical or inclined and their length contributes to determining the total magnification of images. The magnification variable, which can be manual or an electric zoom.

The light sources, which can be incandescence lamps or fiber optics. Illumination in a microscope is necessary because the brightness of the operating field decreases as magnification increases. The illumination systems can be coaxial with the microscope’s optical axis (which has the great advantage of not casting shadows on the field and not changing intensity as magnification changes) or oblique (they avoid direct reflections on the objective).1 A surgical microscope is an essential instrument in modern eye surgery. For phacoemulsification procedures, microscopes must have the features listed next.

-3-

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Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 3-8). © 2014 SLACK Incorporated.

4  Chapter 1

Figure 1-1. The magnification of an object is the apparent size of the object, which is larger the closer the object is to the eye.

Figure 1-2. Projection of the images of an object situated between the ocular and the objective and the relative magnification of the object.

●

Brightness and coaxial highlights all of the ocular structures, even in difficult conditions. The coaxial alignment of the surgeon’s ocular and the operating field, combined with good illumination of the operating field, provides direct visualization of the images of the eye and makes movements during the various phases of surgery easy. It is crucial to have a good view of the anterior capsule, the posterior capsule, and the various planes of the crystalline lens, as well as a good red reflex, without producing a phototoxic effect on the retina and illuminated eye tissues. All surgical microscopes must comply with specific requirements to avoid phototoxic damage. To do so, attention must be focused on the aspects listed next. ○

The characteristic of illumination in research studies2 show the risk of phototoxic damage to the

retina3 can be reduced if the violet and ultraviolet components of light (wavelength below 475 nm) are filtered.4 The possibility of equipping the microscope with a retinal protection filter (blue filter) and a UV filter can reduce the excitation of the retinal cells of the patient and surgeon.5 The orange color of the retina protection filter modifies the color of the microscope’s light, so surgeons must get used to the different appearance of anatomical structures. ○

Illumination intensity should be used at the lowest possible intensity setting on the patient’s eye (ie, the minimal intensity required by the surgeon to be able to see clearly during the operation). For this reason, most modern microscopes have a system that can continuously change the brightness of the light source. This allows the surgeon to adjust the

Microscopes  5 intensity of the light in the patient’s eye as required during the various steps and situations of the operation. ○

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The illumination angle is the area illuminated with the same intensity by a light source. An angular reflector can be used to reverse the direction of the emitted light beam so that the amount of direct light on the macula is reduced (which means lower stimulation). The focus of the light source can inflict phototoxic damage when the spiral filament of the light source is reflected on the patient’s retina. The luminance of a filament is much higher than that of a scattered, uniform light source (eg, a light conductor). For this reason, the most modern microscopes have an illumination system with fiber optics. The duration of the stimulation by the light to reduce illumination can also cause damage. The latest-generation microscopes have protective filters that block light wavelengths that may damage eye tissues.

Red Reflex The red reflex is a specific characteristic of the retina. When stimulated by a coaxial light source, the retina reflects the light and produces a typical red– orange reflection. By analyzing the red reflex, doctors can see if there are alterations in the various ocular media that the light travels through because the alterations reduce or remove the reflex. Corneal opacities, cataracts, retinal lesions, such as myopic atrophy, or the presence of new formations reduce the intensity of the red reflex. In cataract surgery, the red reflex is useful in capsulorrhexis because it allows surgeons to see the anterior capsule well. During cortex removal, it can be used to see remnants from the cataract and the posterior capsule of the lens. Lastly, after insertion of the artificial lens, a good red reflex allows surgeons to easily check that the lens is located properly in the capsular bag.

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Depth of field is required to have many surgical planes in focus at the same time during the various surgical steps. During surgery, the surgeon shifts focus on the various planes (eg, the focus will be on the cornea at the beginning of the procedure [to make accurate incisions] and will then be shifted to the anterior capsule during capsulorrhexis, before being moved again in phacoemulsification and cortex and, finally, when the IOL is inserted in the injector). It is, therefore,

important to have a system that allows the surgeon to move from one plane to another rapidly and easily. ●

Maneuverability allows surgeons to make the required intraoperative adjustments quickly and precisely. In this sense, it is crucially important to have a pedal for the control of magnification (zoom command) and for the translations of the optic lenses (XY command).

Focal distance must provide enough room for the surgeon (and assistant) to operate comfortably under the eyepieces. The focal distance is the area above the operating field in which the microscope moves vertically. There must be enough room for surgeons to work comfortably, but at the same time, the microscope must be able to provide good focus on the eye structures without causing the surgeon to change position. In this way, precise, agile movements are possible. A limited focal distance may make it difficult for the scrub nurse to hand instruments to the surgeon, with the risk of accidentally touching the eye or the nonsterile parts of the microscope head. If the focal distance is too large, the surgeon may have to perform some steps of the operation in an uncomfortable and unstable position. Modern microscopes have a special system that can set the focal distance and the vertical movement range to suit the surgeon according to his or her build. There are different manufacturers of surgical microscopes (Carl Zeiss, Leica, Müller, Topcon, Alcon LuxOR) (Figures 1-3 and 1-4). The most modern microscopes do not just have eyepieces for the main surgeon and the assistant—they also have a video output so the procedure can be directly recorded on a DVD or USB key. In some microscopes (with appropriate systems), HD recordings are possible. 3D images can be obtained by placing two different cameras on the microscope at different angles, so that the film of the surgical procedure looks even more realistic. A monitor in the operating room can be connected through the video output, so the operating team can view the surgery as well. By doing so, the team can organize the preparation of the operating room material for the next patient. They can also prepare the material needed should an intraoperative complication arise, thus creating a better coordinated and more efficient operating room. Surgeons can view the recording of the surgical procedure at a later date and analyze any complications that arose during the operation. The recordings can also be used to create an archive of clinical cases that can be used as material for analysis and study to improve and refine surgical techniques. Lastly, a recording of the surgical operation has legal and medical value should the surgeon have to manage complications or modify the surgery strategy because of an unexpected event. ●

6  Chapter 1

Figure 1-3. Carl Zeiss OPMI Lumera. (Reprinted with permission from Carl Zeiss Meditech AG.)

The innovations in latest-generation microscopes are not limited to surgery recording methods—they concentrate on the visibility of the operating field in terms of illumination, magnification, and zoom. Incandescent lamps are the most frequently used lamps for illumination, although some newer microscopes have LED illumination systems. An LED illumination system provides surgeons with a view of the operating field that is of excellent quality and reduced illumination intensity. Using cold light eliminates the risk of damaging retinal cells because of the lower levels of radiation and filters that block UV/IR rays. Illumination systems that increase the red reflex are available and they can be used to obtain a better view of the anterior chamber during the capsulorrhexis phase. The light angle can be modified, which provides a very clear perception of the size of the intracapsular area during phacoemulsification or irrigation/aspiration procedures. In some cases, the possibility of combining two light sources allows the surgeon to enhance the red reflex instead of field illumination—or the opposite, depending on whether the surgeon is performing capsulorrhexis, inserting the artificial lens, or preparing the operating field.

Figure 1-4. Alcon LuxOR. (Reprinted with permission from Alcon Laboratories.)

By combining an appropriate illumination angle with a field of view of considerable depth, a stereoscopic image of the operating field is obtained, which in turn provides the surgeon with better detail, a brilliant red reflex, and a better distinction of the nucleus and the cortex. Illumination intensity can be managed with a foot pedal, thus allowing the surgeon to work through each part of the operation with the most suitable light. During surgery preparation and at the end of the surgical procedure, the possibility of having an electromagnetic locking system allows surgeons to move the microscope head easily into the most convenient position. Some instruments have a dual speed focusing mechanism, which allows surgeons to rapidly change the focus according to surgery-related needs (eg, in the final phases of intraocular lens [IOL] loading, surgeons can rapidly switch from focusing on the operating field to focusing on the IOL cartridge, without moving the microscope head and then immediately return to the initial position). The microscope foot pedal has many commands that enable the surgeon to modify illumination intensity, zoom, and focus; the section of the illumination angle; and XY position, without the aid of an assistant. Surgeons can set

Microscopes  7

A

B Figure 1-5. Detail of the Carl Zeiss Lumera 700 microscope with the vitreoretinal surgery kit attached to it. (Reprinted with permission from Carl Zeiss Meditech AG.)

the various pedal commands by choosing the position of the focus and magnification on the foot pedal in the position they find most comfortable and ergonomic. Other functions can be set, such as the insertion of the keratoscope and slit lamp, intraoperative aberrometer, and rapid magnification change. A Wi-Fi pedal makes it easier for surgeons to move, as there are no obstructing connection cables. The operating team can move around the patient more easily, without the danger of hindering surgical activity. The microscope’s oculars have lenses to correct the refractive error of the surgeon and assistant. Interpupillary distance can be modified as well. Finally, some of the latest microscopes have a separate and independent viewing system for the assistant, which allows him or her to have a better view of the operating field. The most recent microscopes have an additional system of lenses that can be used to view the vitreous chamber and the posterior segment rapidly by using foot pedal commands. In addition, good illumination of the vitreous chamber is obtained using an independent fiber optic. In this way, surgeons can use both hands during intravitreal surgery procedures (Figure 1-5). This last detail is particularly important when dealing with complications during cataract surgery, especially in the case of rupture of the posterior capsule, with material dropping into the vitreous chamber. To make using the microscope and performing the surgery comfortable, the surgeon should have a special chair with armrests, which allows him or her to sit in a comfortable position during surgery. The chair’s height must be adjustable and the surgeon must be able to place his or her elbows on the armrests. This means that it is not necessary

Figure 1-6. The height of the surgical armchair can be adjusted. During patient preparation, the operating team can instill anesthetic drops, then the bed is adjusted so that the surgeon can operate comfortably.

to perform surgery with raised arms, which, over time, can become uncomfortable and cause shaking. Furthermore, if a surgeon is uncomfortable during surgery, his or her movements will be neither fluid nor easy.

SURGICAL BEDS AND CHARACTERISTICS NEEDED FOR OPHTHALMIC SURGERY The first and most important characteristic is stability. Patients must be placed in a comfortable position so that they are at ease throughout the operation, which in turn will reduce involuntary movements during surgery. The height of the patient’s surgical bed should be adjustable. There must be a mechanism to adjust the head of the bed, so the patient’s head is in a comfortable position during and after surgery, when the patient must stand up and leave the operating room. This is also important for the surgeon, who can position the microscope and adjust the height of the chair so that he or she is operating in a correct and comfortable position (Figure 1-6).

8  Chapter 1

Figure 1-7. Surgical armchair in an upright position so the patient can sit down easily.

Figure 1-8. Surgical armchair in the operating position, with a locking system, separate movement of the headrest and air tube.

patient is covered by a sterile surgical drape and may feel he or she is not getting enough air (Figures 1-7 and 1-8). During outpatient surgery, reclinable armchairs may be used, so that patients can sit and stand again easily and effortlessly. By using the commands on a foot pedal or a remote control, the height of the armchair seat, the inclination of the backrest, and the height and inclination of the headrest can be adjusted (Figure 1-9).

REFERENCES Figure 1-9. Surgical armchair positioned so the surgeon can operate comfortably.

1. 2.

The bed should have a locking system that stops any accidental movement. A support table is also a useful feature. A ventilation system is useful because it provides the patient with the right supply of air and oxygen under the surgical drape. The ventilation device is simply a metal or plastic tube connected to an aeration system enriched with oxygen and with openings for air to move through. The arch-shaped tube is put in front of the patient’s mouth and nose in order to allow the right supply of air during surgery, when the

3.

4.

5.

AA.VV. Progressi clinici—Chirurgia_ Microchirurgia clinica. Piccin. Sznitman R, Rother D, Handa J, Gehlbach P, Hager GD, Taylor R. Adaptive multispectral illumination for retinal microsurgery. Med Image Comput Comput Assist Interv. 2010;13(Pt 3):465-472. Kweon EY, Ahn M, Lee DW, You IC, Kim MJ, Cho NC. Operating microscope light-induced phototoxic maculopathy after transscleral sutured posterior chamber intraocular lens implantation. Retina. 2009;29(10):1491-1495. Hunter JJ, Morgan JI, Merigan WH, Sliney DH, Sparrow JR, Williams DR. The susceptibility of the retina to photochemical damage from visible light. Prog Retin Eye Res. 2012;31(1):28-42. Glickman RD. Ultraviolet phototoxicity to the retina. Eye Contact Lens. 2011;37(4):196-205.

2 Surgical Instruments Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Cataract surgery is microincisional surgery for which specific instruments are required. Different instruments are used in every step of phacoemulsification with implantation of an artificial lens. Surgical instruments can be classified as follows: Surgical blades

directly into the corneal tissue and is more suitable for side ports (Figure 2-2). ●

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Forceps

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Manipulators

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Cannulas The knives used to perform corneal and scleral incisions are listed next. 3.2, 3.0, 2.75-mm knives are tapered, double-edged steel blades used to perform the scleral and corneal tunnel incisions. The incision has a calibrated width. The sizes are used to create a tunnel for the access of traditional phaco tips (not microincision cataract surgery [MICS] tips). ●

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2.2, 2.0, 1.8-mm knives for MICS have the same tapered shape as the ones mentioned previously, but they are smaller. These knives are used to create the main tunnel and allow access to the latest-generation new MICS phaco tips (Figure 2-1). Knives with 15- or 30-degree blades have their cutting edge at a predefined angle (15 or 30 degrees). The knife is used to perform preincisions of the tunnel and sideport incisions. The 15-degree knife has the same shape as the 30-degree knife, but it is more acute (15 degrees). It is used for the same purpose. The cutting edge of a 15-degree angle allows the surgeon to penetrate

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Crescent knife has a blade with a defined width, medium length, blunt edges, and cutting edge. Because of its flat support base, it is used to cleave the layers of scleral tissue and to create the main tunnel (Figure 2-3). Diamond knife with micrometer adjustment has a diamond blade and tapered shape and is available in different sizes. Micrometer adjustment can be used to precalibrate and set the amount of the blade’s protrusion and, therefore, the exact depth of the preincisions perpendicular to the corneal tissue. The same scalpel with a fully extended blade can be used to perform the corneal or scleral tunnel. A net incision is obtained, with regular, precise margins. Other knives with precalibrated widths and sharp and blunt tips are available in various sizes (1.8, 2.0, 2.75, 3.2, 5.0, and 6.0 mm) and can be used to enlarge the previously created tunnel. This tunnel will be used to introduce the soft or rigid artificial lens into the anterior chamber (before positioning it into the capsular bag). The most commonly used forceps are listed next. Corneal forceps are surgical forceps for microsurgery that have teeth to grip corneal tissue without causing trauma. Hoskin forceps are surgical forceps that do not cause trauma because the nontoothed tips are designed to create two small linear planes that lock against each other. The special geometry means the scleral tissue can be

Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 9-16). © 2014 SLACK Incorporated.

10  Chapter 2

Figure 2-1. Alcon 2.2-mm keratome. (Reprinted with permission from Alcon Laboratories.)

Figure 2-2. Alcon 15-degree blade. (Reprinted with permission from Alcon Laboratories.)

A Figure 2-3. Alcon 2.3-mm crescent knife. (Reprinted with permission from Alcon Laboratories.)

B

A B Figure 2-5. Folder and holder forceps for acrylic IOLs. (Reprinted with permission from Janach.)

Figure 2-4. (A, B) Buratto coaxial capsulorrhexis forceps (manufactured by Janach). (Reprinted with permission from Janach.)

grasped without causing trauma or laceration. For this reason, it is used mainly during scleral tunnel preparation and in glaucoma surgery (scleral flaps). ●

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Conjunctiva forceps and colibri forceps are surgical forceps with strong gauge teeth and are designed to provide a firm grip of the conjunctival tissue. The curved, unusual profile shape of these forceps is vaguely similar to a hummingbird. Capsulorrhexis forceps, with sharp tips, can be used to cut the anterior capsule of the lens directly so a cystotome is not required. With a precise, rotating movement, using the same forceps and without introducing other instruments, capsulorrhexis of the anterior capsule can be performed. Coaxial capsulorrhexis forceps1 have a coaxial action (vitreous forceps type) and a 23-gauge diameter shaft. The very small size of these forceps allows surgeons to perform capsulorrhexis through a small corneal microincision (1.8 to 2.0 mm). The tips can be sharp or blunt (Figure 2-4). Tying forceps are used for suturing. The jaws can be straight or curved. The smooth, even planes lock into one another, so the suture material can be gripped and held. McPherson forceps are similar to tying forceps (with similar plane geometry), but its jaws are at a 45-degree angle (approximately). It is used for a number of purposes such as gripping the soft artificial lens (3-piece IOL) and loading it into the cartridge, leading and inserting the loops into the anterior chamber in the capsular bag, and performing intracameral sutures during iridoplasty.

Figure 2-6. Janach straight needle holder for microsurgery. (Reprinted with permission from Janach.)

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Forceps to load one-piece acrylic lenses have special nontraumatic blunt-plane geometry that provides a good grip on the artificial lens without damaging or scratching it. Forceps to insert foldable lenses (folder and holder) perform a specific task in rapid succession: the folder forceps are used to fold the artificial crystalline lens, which is loaded and inserted by the holder forceps through the incision of the main tunnel (Figures 2-5). Forceps to insert rigid lenses have jaws made of two round plates with a slightly ridged internal surface, which provides a good grip on the lens, perfect control, and excellent manageability. Prechopper/cracking forceps have paddle jaws with opposing action that, in the case of cracking forceps, can be used to perform division of the cataract nucleus after the creation of the cross with phacoemulsification or, in the case of prechopper forceps, the creation of a pregroove before using ultrasound. Needle holders are straight or curved, with or without lock, and used for sutures (Figure 2-6). It is used with the previously described tying forceps. Manipulators are described next.

Surgical Instruments  11

A

A

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Figure 2-7. Janach olive-tip spatula. (Reprinted with permission from Janach.)

Figure 2-8. Janach chopper. (Reprinted with permission from Janach.)

Olive-tip spatulas are a round, blunt-end spatula used to rotate and mobilize the nucleus during phacoemulsification. It can be inserted through a side-port incision to stabilize the eye during phacoemulsification or at the beginning of surgery during the execution of the preincisions and the corneal tunnel or during capsulorrhexis.2 If areas of the iris have adhered to the anterior surface of the lens, this spatula is useful in detaching them (Figure 2-7).

preparation of the scleral–corneal tunnel to incise the conjunctiva to perform sub-Tenon’s block and in filtering operations).7

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Chopper hooks have a small blade on the inside of the hook. Used during surgery, they have different shapes and cutting angles and, combined with the action of the ultrasound phaco probe,3 help divide the cataract nucleus. They allow surgeons to grasp or cut the nucleus that, once divided,4 is captured and fragmented by the ultrasound probe (Figure 2-8).5 Lens hooks are straight, without cutting edges, and used to insert and guide the rigid loops of intraocular lenses into the capsular bag. This hook can be used after inserting the artificial lens to rotate the lens in the capsular bag and put it in the best position. It is also used to mobilize any remaining cortical remnants, which can be aspirated in the following step (aspiration of the viscoelastic substance). Iris hooks are hooked, blunt, and used to retract/shift and manage the manipulation of the iris tissue, especially if there are synechiae or if there are adherences between the iris and the lens or cornea. Push–pull hooks are generally T-shaped and are used to manipulate the iris working on the pupillary sphincter, push or retract the pupil edge, and keep trauma to a minimum. If a pair is used, pupil stretching can be performed.6 Scissors are listed next. Conjunctival scissors, with blunt, large tips, are used for various kinds of conjunctival incisions (eg, in the

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Vannas scissors are narrow, with straight or curved blades, and used in various ways in the anterior segment. They are also used to perform iris sphincterectomy. Coaxial Sutherland scissors are straight or curved. Because of their special geometry and very small size of the 20/23-gauge pivot, these microscissors are used in microincisional surgery in the anterior chamber. This makes them useful in the removal of synechiae or if the capsulorrhexis needs to be enlarged (secondary capsulorrhexis), sphincterectomy is required, or threads in the anterior chamber need cutting (eg, in iridoplasty). Needles and cannulas are listed next. Cystotome is a 27-gauge needle with the tip bent down at a 45-degree angle. It is used to make an incision in the anterior capsule, which is then gripped with forceps to perform a continuous capsulotomy. It can be used to perform capsulorrhexis as well. Anterior chamber cannula is used to inject balanced salt solution (BSS), anesthetics, antibiotics, and saline solution into corneal incisions during the hydration final step. Cannula for hydrodissection and hydrodelineation of the lens is a cannula with an open front with an elliptical section. The most innovative version has a tip that has a slight downward angle (approximately 45 degrees), which provides perfect control during BSS injection and can rest on the lens while performing rotation during cortical detachment (Figure 2-9). ○

0.5-mm cannula is Rycroft (anterior chamber) type and angled. One of its uses is the manual aspiration of viscoelastic material.

12  Chapter 2

Figure 2-9. Buratto hydrodissection cannula—the cannula’s curvature allows the surgeon to reach the equatorial region of the lens to perform adequate hydrodissection.

Figure 2-10. Single-use kit of surgical instruments for cataract surgery. Generally, these kits include corneal forceps, lid speculum, manipulator, capsulorrhexis forceps, and the irrigation/ aspiration handpiece if the monomanual technique is used. The kit can be assembled with the instruments the surgeon prefers.

Figure 2-11. Phacoemulsification handpiece with sleeve. The diameter of the sleeve varies depending on the tip diameter used.

Figure 2-12. Tip of the phaco handpiece—Kelman model. There are straight tips and tips with different angulations.

Finally, there are disposable kits available for use in cataract surgery. They contain all of the necessary instruments and are ideal for operations performed on HIV patients or carriers of viral hepatitis. These kits reduce the risk of cross-contamination between patients, though the risk is very small with standard resterilized instruments (Figure 2-10).

reduce phacoemulsification times and make cataract fragmentation more effective (Figures 2-11 and 2-12). The irrigation and aspiration probes11 can be separated if the procedure is performed with the bimanual technique.12 Alternatively, they can be coaxial (ie, in a single probe [coaxial technique]).13 The tips of these probes can be ridged in order to remove cortical residue from the posterior capsule more effectively. The diameter of the opening in the aspiration probe can be of different sizes in order to increase the capacity to remove cortical fragments. Sometimes, when operating on soft cataracts, the aspiration probe is enough and the handpiece with ultrasound is not necessary. A speculum is a small “retractor” that is used to open the patient’s eyelids during surgery. It can be single (in which case two are used, one on each lid) or bivalve (in which case it has a screw to open and close it). Depending on the position of the screw, it can be nasal or temporal. The advantage of two single speculums is that trauma on palpebral muscles is reduced. Each speculum has an elastic, which is secured to the surgical drape with Klemmer forceps and can be used to obtain good exposure of the eye. Normally, one single speculum is placed on the lower eyelid and one on the upper eyelid.

THE INSTRUMENTS OF THE PHACOEMULSIFICATION DEVICE The handpieces of the phacoemulsification device8 have an ultrafine tip that can be straight or curved (Kelman).9 The handpiece has a coaxial sleeve with two side ports, through which BSS irrigation can be continuous and the microfragments of the lens (emulsified when phacoemulsification is active) can be drawn out.10 The purpose of the sleeve is to direct the flow of fluid into the eye and to cool the tip of the handpiece. It also protects the entry tunnel from damage that could be caused by the tip overheating. Some of the tip’s special kinds of movements (oscillatory, torsional, or bidirectional) can improve and optimize the instrument’s capacity to fragment and emulsify the cataract. The multidirectional movements of the handpiece tip

Surgical Instruments  13

Figure 2-13. Buratto nasal open-valve lid speculum.

Figure 2-14. Single-use injector with cartridge. Using a singleuse injector increases safety and reduces the risk of postoperative inflammation and infections caused by a nonperfect sterilization process.

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Figure 2-15. Sterilizable injector for single-piece lenses. The lens placed in the cartridge folds into itself during injector preparation and opens up again in the eye during the injection phase. ●

Bivalve speculums can have open or closed loops— closed ones are usually better at keeping eyelashes out (Figure 2-13). Positioning a speculum correctly is an important step in cataract surgery, as good exposure of the globe without causing too much discomfort to the patient allows the surgeon to view the operating field clearly, which, in turn, means he or she can perform precise incisions and surgical maneuvers without causing the patient to twitch or move suddenly. Artificial IOL injectors can have a screw or a plunger. They have a compartment for the cartridge into which the foldable artificial lens will be placed. Once loaded, the lens—appropriately folded in the specific cartridge—is ready to be injected into the capsular bag. Injectors can be single-use devices or they can be sterilizable (Figures 2-14 and 2-15). Injectors for preloaded IOLs are made of disposable material. The cartridge can be integrated or there can be a slot for the external cartridge. In both cases, the IOL is preloaded and blocked by small supports made of plastic material, which can be removed, allowing the surgeon to inject the artificial lens. The main advantage of using injectors with preloaded lenses is the reduced manipulation of the IOL (excessive manipulation can damage the IOL’s integrity). These devices also ensure that the IOL is loaded correctly, which makes them easier to inject and reduces the risk of breaking them.

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Here is a list of a few particular accessory instruments. Thornton fixation ring is made of a mobile ring that is open at the front to allow the blade to pass during the corneal incision. Its purpose is to fixate the globe using a nontraumatic indentation created by blunt teeth on the lower side. Easy fixation ring is a stiletto with a 5-mm flat base, with two lateral, small indenting teeth that, placed on the corneal surface, stabilize the eye during the creation of corneal incisions. Four single-use iris hooks (sterilizable re-usable iris hooks, such as MacKool’s hooks, are available) are very useful, flexible devices used with iris-lens synechiae or if there is a miotic pupil that does not respond to drugs. They are also helpful with intraoperative floppy iris syndrome (IFIS).14 Once positioned, they can be used to retract the iris, thus providing a good view of the anterior surface of the lens. In cases of complex cataract surgery in which the capsular bag is particularly unstable, these hooks can be used to support the capsular bag and to stop the zonules from detaching during phacoemulsification (Figures 2-16 and 2-17). Malyugin iris retractor with injector is a disposable pupil-dilation system that has a single-use injector that makes it easier to insert. Only one incision (2.2 mm in diameter) is needed for the insertion and removal of a Malyugin ring.15 The ring’s diameter can be 6.5 or 7.25 mm. Because of its shape, the ring allows surgeons to obtain circular pupil dilation with little traction on and mechanical damage to the pupillary edge (Figure 2-18). Other iris retractors can be single-use or sterilizable systems. By allowing surgeons to obtain good pupil dilation, they make phacoemulsification of the nucleus possible, reducing the risk of trauma to iris tissue (such as the Arne ring).16

14  Chapter 2

Figure 2-16. Single-use iris hooks. They are inserted through a corneal incision made with a 30-degree blade (or 19 to 20 gauge). The hooked end is used to engage the pupillary edge and, by sliding the designed silicone block, the hook is locked into place and the pupil opened.

Figure 2-18. Malyugin iris ring properly positioned to obtain a good view of the capsular bag and lens during phacoemulsification.

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Capsular tension ring is used in case of zonular laxity with a poorly stable, weak capsular bag (ie, when there is a high risk of dislocation or luxation of the artificial lens). There are various models available. Listed below are a few examples.17 ○

Corneal capsular tension ring confers stability to the capsular bag, even if the zonules are fragile. It prevents retraction of the posterior capsule. Various sizes are available, depending on the characteristics

Figure 2-17. Single-use iris hooks. Final appearance of the pupil after the four iris hooks have been positioned.

Figure 2-19. Technique for positioning capsular tension rings using forceps.

of the eye. It is inserted into the capsular bag with the aid of forceps and a manipulator. The ring is inserted through the secondary incision into the anterior chamber and capsular bag. The tip of the manipulator hook is inserted into the specific eyelet on the ring, which is used to guide it into the capsular bag (Figure 2-19).

Surgical Instruments  15

A

Figure 2-20. Details of capsular tension ring during the injection in the capsular bag.

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Injector for the tension ring is used for controlled insertion of a capsular tension ring to support the bag (Figure 2-20).

Cionni endocapsular tension rings, or ring segments, have small eyelets that are used to place them correctly in the capsular bag and to fix the rings (or segments) into the sclera to avoid dislocation of the capsular bag. The Cionni ring is used mainly in the case of subluxation of the lens (Figures 2-21 and 2-22). Sutures and needles are listed next. 10/0 nylon is the most commonly used material in cataract surgery. The arc-shaped needle is double edged in order to make penetration into the corneal and scleral tissue easier. It can be single or double armed, depending on whether there is a needle on one end of the suture or both. ○

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10/0 Prolene is used for iris suture if iridoplasty is required to reduce pupillary diameter, excessively large iridectomies, or the result of iris trauma involving the iris root. The suture may be single or double armed (needles on both ends of the suture). The shape of the needle can be modified by using a needle holder in order to make the entry into the anterior chamber and the capture of iris tissue easier, so it can be sutured. 10/0 Prolene can also be used to fix the sclera to rigid scleral-suspended lenses, when the patient does not have a posterior capsule or if the capsule itself does not ensure adequate support for the artificial lens. The two ends of the suture are attached to the same needle, which is curved, narrow, and about 0.7 to 0.8 cm in length, in order to create a buttonhole around the loop of the artificial lens with scleral suspension and then fix it, via sclerotomy, to the scleral wall. Surgical drapes are listed next.

Figure 2-21. Examples of capsular tension ring models.

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Patient’s surgical drape is made of plastic. It has a transparent, adhesive square that is first placed onto the eye undergoing surgery and then cut in order to expose the eye and position the speculum.

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Figure 2-22. Capsular tension ring attached to the margin of anterior capsulorrhexis inserted into the capsular bag.

The drape can have a fenestration to expose the eyelids and the eye (in this case, Tegaderm dressings, etc, are required). It is important that the adhesive area is made to adhere properly to grasp the eyelashes and keep them away from the operating field. The drape may cover the patient completely or partially. On the side of the adhesive square, there are fluid-collection pouches for the saline solution used during the phacoemulsification procedure. ●

Transparent fenestrated drape is a small, transparent drape with a fenestration that is positioned on the eye undergoing surgery. A Tegaderm dressing must be used to keep eyelashes away before positioning the speculum. It has pouches for fluid collection. It is suitable for claustrophobic patients.

REFERENCES 1.

Kesarwani SS, Sahu SK. Push-pull technique of capsulorrhexis for fibrous plaques on anterior capsules in pediatric cataract surgery. J AAPOS. 2011;15(5):493-494.

6. 7.

8. 9.

10.

11. 12. 13.

14.

15.

16.

17.

Mahr MA, Hodge DO. Construct validity of anterior segment anti-tremor and forceps surgical simulator training modules: attending versus resident surgeon performance. J Cataract Refract Surg. 2008;34(6):980-985. Aslan BS, Müftüoglu O, Gayretli D. Crater-and-split technique for phacoemulsification: modification of the crater-and-chop technique. J Cataract Refract Surg. 2012;38(9):1526-1530. Kim DY, Jang JH. Drill and chop: modified vertical chop technique for hard cataract. Ophth Surg Lasers Imaging. 2012;43(2):169-172. Erakgun T, Akkin C, Afrashi F. Illuminated endochopper in the management of posteriorly dislocated lens nucleus. J Cataract Refract Surg. 2005;31(9):1697-1698. Vasavada AR, Raj SM. Multilevel chop technique. J Cataract Refract Surg. 2011;37(12):2092-2094. Riad W, Ahmad N, Kumar CM. Comparison of metal and flexible sub-Tenon cannulas. J Cataract Refract Surg. 2012;38(8): 1398-1402. Fishkind WJ. The phaco machine: analysing new technology. Curr Opin Ophthalmol. 2013;24(1):41-46. Han YK, Miller KM. Heat production: longitudinal versus torsional phacoemulsification. J Cataract Refract Surg. 2009; 35(10):1799-1805. Balantas V, Young K, Athanasiadis Y, Sullivan P, Hussain B, Saleh GM, “PhacoTracking”: an evolving paradigm in ophthalmic surgical training. Ophthalmology. 2013;21: 1-3. Agarwal A, Agarwal S, Agarwal A, Maloof A. Sealed-capsule irrigation device. J Cataract Refract Surg. 2003;29(12):2274-2276. Nichamin LD. Endoilluminated infusion cannula for anterior segment surgery. J Cataract Refract Surg. 2012;38(8):1322-1324. Menapace R, Di Nardo S. Aspiration curette for anterior capsule polishing: laboratory and clinical evaluation. J Cataract Refract Surg. 2006;32(12):1997-2003. Tsai CH, Hsiao CH, Ku WC. Flexible iris retractors for management of zonular dialysis during planned phacoemulsification. Chang Gung Med J. 2006;29(5):499-504. Wilczynski M, Wierzchowski T, Synder A, Omulecki W. Results of phacoemulsification with Malyugin Ring in comparison with manual iris stretching with hooks in eyes with narrow pupil. Eur J Ophthalmol. 2013;23(2):196-201. Sauer T, Mester U. Tilt and decentration of an intraocular lens implanted in the ciliary sulcus after capsular bag defect during cataract surgery. Graefes Arch Clin Exp Ophthalmol. 2013;251(1):89-93. Werner L, Zaugg B, Neuhann T, Burrow M, Tetz M. In-the-bag capsular tension ring and intraocular lens subluxation or dislocation: a series of 23 cases. Ophthalmology. 2012;119(2):266-271.

3 Patient Selection Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD During the eye examination, it is important to assess some patient-related factors that will be very important at the time of surgery.1 The first factor to consider for patient selection is age; young patients have soft cataracts that are difficult to manipulate, whereas older patients are more likely to have large, hard cataracts that are often associated with more fragile eye structures and atrophic tissue.2 An accurate medical history provides information on whether the patient has medical conditions or is taking medication that could cause alterations in the eye, which require pre-, intra-, and postoperative arrangements in order to perform surgery in the safest conditions. Systemic diseases such as diabetes, noncompensated hypertension, anxiety and psychological disorders, depression, pulmonary emphysema, and bronchopathies must be identified and investigated. The use of drugs for prostatic hyperplasia, cardiac arrhythmia, or the use of psychiatric medication, anticoagulants, antihypertensives, and vascular disease affecting the major vessels in the neck—which can make ischemia and thrombosis in the retina more likely—must also be identified and investigated. The same applies to allergies to drugs, environmental antigens, foods, or materials used in surgical procedures. It is always important to gather information on the patient’s eye history, which includes episodes of intraocular inflammation (such as uveitis and panuveitis), retinal detachment and retinal argon laser treatments, previous corneal refractive surgery, glaucoma surgery, and retinal surgery.3 We will now analyze each of the crucial aspects in the preliminary examination of a patient who is a candidate for cataract surgery.

MEDICAL HISTORY It is important to know (or to exclude) the presence of diabetes mellitus.4 If the patient is diabetic, then it is useful to know if the condition is insulin dependent or non–insulin-dependent5; for how long the patient has been affected; if the currently used therapy is effective; and if the disease has damaged organs such as the kidneys, heart, and peripheral vascular system. The patient’s glycemic conditions can affect the surgery. Stress can cause glycemia to rise, so the administration of a mild tranquilizer can help these patients.6 Being aware of these elements enables ophthalmologists to assess the stage of the disease in terms of severity in order to assess possible intraoperative complications and risks.7 It is also crucial to know about systemic effects of the disease in order to formulate a prognosis on the positive effects (in terms of visual improvement) the patient may have after cataract surgery. Obviously, the postoperative recovery of vision of a patient with long-term diabetes,8 with poor glycemic compensation, and with signs of advanced damage to retinal circulation will be very limited. On the contrary, a patient who has been suffering from diabetes for only a few years, whose glycemic compensation is good, and who has no alteration in retinal circulation can be expected to recover as well as a healthy person.9 It is also important to remember that operative risks will be much lower in the second situation than in the first. The quality of glycemic control and the kind of current therapy (oral antidiabetic drugs or insulin therapy) in patients with diabetes must be documented. If the patient’s medical history includes previous retinal argon laser treatment for complications caused by diabetic retinopathy,

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Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 17-23). © 2014 SLACK Incorporated.

18  Chapter 3

Figure 3-1. Retinal angiography in a patient with early stages of diabetic retinopathy. Diffusion of fluorescein in the microaneurysms can be seen.

Figure 3-2. Ocular fundus of a patient with arterial hypertension with poor therapeutic control. Peripheral hemorrhages, peripapillary exudates, and arteriovenous nicking can be seen.

retinal angiography (Figure 3-1) and preoperative optical coherence tomography (OCT) are required10 in order to understand postoperative prognosis. If the patient has poorly compensated diabetes, satisfactory glycemic control should be established before surgery.11 Another condition that requires investigation is hypertension (Figure 3-2). It is necessary to check that patients with hypertension are, at the time of surgery, taking effective medication that keeps blood pressure levels in a normal range, without wide oscillations in systolic and diastolic values.12 High intraoperative blood pressure can cause intraocular hemorrhage and the ocular pressure that follows can make cataract surgery difficult. Sometimes, in this situation, surgery must be stopped and postponed until the intraocular pressure and blood pressure have returned to normal levels. The use of phenylephrine drops for pupillary dilation (used during patient preparation) must be limited in hypertensive patients. If anxiety causes blood pressure levels to rise above 180/100 mm Hg, the administration of a tranquilizer can be useful. If values fail to return to normal, an antihypertensive drug can be administered via the oral or sublingual route. In patients with cardiovascular diseases or vasculopathies, it is important to request an accurate cardiovascular examination (which assesses the operative risk and the anticoagulant therapy used by the patient).13 In most cases, although the surgical procedure is performed with topical anesthesia, the examination is important because sometimes local regional anesthesia (peribulbar injection of the anesthetic) is required, especially if the patient is not cooperating. In the case of retinal vascular disease (such as partial retinal vein occlusion or central retinal vein occlusion), surgeons should check the clinical status of the retina and, if necessary, perform argon laser treatment before cataract surgery. Heart conditions such as cardiac arrhythmia or atrial fibrillation must be investigated—not just to assess intraoperative risks but also because the medication used to treat

these conditions can have specific side effects; for example, the chronic use of drugs, such as amiodarone, can cause the formation of intracorneal deposits. The formation of cloudy areas in the cornea makes it more difficult to see the anterior capsule during capsulorrhexis. If doctors know of this condition in advance, they can plan to use trypan blue (dye) on the anterior capsule, which makes the execution of capsulorrhexis easier. There is no need to stop or change the therapy of patients on anticoagulants, but it is useful to plan surgery so that it is performed with local topical anesthesia and that clear corneal incisions are used to avoid bleeding. However, if surgery needs to be performed with deeper local regional anesthesia, with bulbar block, the dose of anticoagulants taken by the patient must be reduced. Patients with respiratory problems must be assessed for coughing symptoms, which can cause complications during surgery. In these cases, administering a cough sedative before surgery is recommended. With regard to other drug therapies, there are other drugs that can make some surgical procedures more difficult if surgeons do not know about them in advance; for example, therapies for treating prostatic hyperplasia14 induce a permanent alteration in the iris that causes the so-called floppy iris syndrome,15 which, if not diagnosed before starting, can cause complications during cataract surgery16 (ie, miosis can occur during surgery, the iris can prolapse into the incision [Figure 3-3], which makes cataract procedures more difficult).17 In these cases, during patient preparation, the use of atropine eye drops should be included to dilate the pupils in a more reliable manner. High-molecular-weight viscoelastic substances should be used with the aim of keeping the anterior chamber and the anterior capsule more stable during the capsulorrhexis phase. To reduce the risk of iris prolapse in the incisions, clear corneal incisions should be made further away from the iris. Surgeons should exercise extra caution during the irrigation/aspiration phase and removal of cortex in order

Patient Selection  19

Figure 3-3. Iris prolapse in a wound in a patient with floppy iris syndrome.

Figure 3-5. Congenital subluxation of the crystalline lens, often associated with Marfan syndrome.

to avoid accidental laceration of the pupillary sphincter, which could be hypotonic postoperatively (to make this particular step easier, a preservative-free vial of adrenaline can be diluted in the balanced salt solution [BSS] bottle). Sometimes, it can be useful to position iris hooks in order to perform the surgical procedure more safely, with a good view of the anterior capsule during capsulorrhexis and of the capsular bag during phacoemulsification and irrigation/aspiration (Figure 3-4). Another consideration is the identification in patients’ features that can be linked to Marfan syndrome (height, very long upper and lower limbs). In patients with this syndrome, the structures supporting the lens can be very fragile18 and, on performing a slit lamp examination, surgeons

Figure 3-4. Positioning of iris hooks in a patient with intraoperative floppy iris syndrome (IFIS). The 4 iris hooks are in opposite positions in order to obtain adequate and symmetrical dilation of the pupil.

must check for possible luxation of the lens. If these characteristics are recognized, appropriate precautionary measures can be taken to avoid certain intraoperative complications, such as vitreous loss, capsule detachment, and loss of lens material into the vitreous (Figure 3-5). Appropriate investigation is required when dealing with patients with epilepsy, Alzheimer’s disease, or neurological disorders in order to establish the most appropriate approach to surgery. Finally, it is important to enquire about allergies to drugs or materials such as latex and tape. If the patient is allergic to or has had hypersensitivity reactions to these materials, it should be written down, so that latex-free surgical material and hypoallergenic paper tape can be used. Today, a latexfree version of every material used in surgery is available. Finally, it is important to remember to ask the patient if he or she is claustrophobic so that the operating field can be prepared using sterile transparent drapes.

Eye Condition: Specific Medical History With regard to previous eye conditions, surgeons should assess the presence of angle-closure glaucoma19 (Figure 3-6) because this condition requires one or two YAG laser iridotomy procedures to be performed before cataract surgery.20 In this way, during patient preparation, good pupillary dilation can be obtained without the risk of elevated intraocular pressure.21 It also allows the surgeon to consider any accessory maneuvers during cataract surgery, such as the possibility of performing gonioplasty 22 with

20  Chapter 3

Figure 3-6. Visante image of patient with angle-closure glaucoma.

Figure 3-7. Cataract with pseudoexfoliation syndrome.

Figure 3-8. Pseudoexfoliation syndrome of the anterior capsule. The whitish deposits that can be seen on the anterior surface of the lens capsule are the result of contact and rubbing of the posterior surface of the iris on the anterior capsule of the lens.

the viscoelastic substance.23 In the case of a previous, acute glaucoma attack, the residual function of the pupillary sphincter and the presence of synechiae and adherences between the iris and the anterior region of the lens must be analyzed24; for example, the presence of fixed mydriasis negatively affects vision in mesopic conditions.25 In the case of a patient with open-angle glaucoma, intraocular pressure should be recorded and plotted in a tonometry curve determined in the weeks preceding cataract surgery in order to be sure there is good pharmacological control of the condition. If intraocular pressure values are high, locally administered drugs can be combined or diuretics can be administered via the oral or parenteral route. It is also useful to have information about the visual field to check and verify if there are signs of rapid and progressive deterioration or if, on the contrary, it has been stable for a long period of time. In the case of patients with glaucoma associated with pseudoexfoliation syndrome,26 the anterior capsule can be very fragile so it is important

to use viscoelastic substances with high molecular weight during capsulorrhexis,27 in order to control the opening of the capsule without risking its rupture or escape.28,29 It is also important to have a capsular tension ring available30 to stabilize the capsular bag before introducing the artificial lens31 (Figures 3-7 and 3-8). It is useful to know about previous intraocular inflammation episodes, such as anterior or posterior uveitis or the presence of recurrent uveitis, as they could be associated with the deposit of inflammatory material on the corneal endothelium, which can prevent the surgeon from having a good view of the anterior chamber and the anterior capsule. Additionally, the pupil may be constricted and not react to the drugs used for pupillary dilation because of the presence of synechiae between the iris and the anterior capsule.32 In these cases, it is useful to use iris hooks (or other devices for appropriate mechanical mydriasis) and spatulas that can remove the adhesions and dilate the pupil as required.33 Specific investigations for corneal study are required for patients who have previously undergone refractive surgery or corneal transplantation or are affected by corneal pathologies, such as keratoconus,34 because keratometric and axial length data are crucially important for calculations related to the artificial lens35 that is implanted during cataract surgery.36 Atrophied iris tissue can cause persistent mydriasis, which causes the patient to have impaired vision. In these cases, it can be useful to perform postoperative “pupillary gymnastics,” which is done by applying eye drops containing drugs with miotic action in the morning and with mydriatic action in the evening. Finally, in the cases of severely atrophied iris tissue, the surgeon may consider performing

Patient Selection  21

Figure 3-9. Patient with keratoconus. Using a slit lamp, the severity of corneal protrusion and the presence of folds, streaks, and opacity on the cone apex can be seen.

Figure 3-10. Phakic lens and congenital cataract. In this patient, the decentration of the phakic IOL is considered the cause of the eccentric vision of the patient, who has nystagmus as well.

intraoperative iridoplasty, suturing the iris to reduce pupillary diameter. The presence of noncompensated keratoconus with extensive corneal opacity 37 or the presence of corneal opacity caused by trauma or previous infections may require open-sky cataract surgery and keratoplasty at the same time (Figure 3-9). In cataract surgery associated with penetrating keratoplasty, intraocular lens (IOL) calculation may be inaccurate for various reasons, including residual, postoperative astigmatism induced by corneal sutures,38 but especially because of pre- and postoperative curvature variations, as well as unreliable preoperative keratometry readings. However, if the patient has had penetrating keratoplasty before cataract surgery, the surgeon may consider implanting a toric lens,39 which can partly or completely correct any existing astigmatism.40 Previous refractive corneal surgery, such as excimer laser41 or radial keratomy, must be documented because during IOL calculation,42 correction formulas must be applied in order to obtain the correct value of the artificial lens to be implanted after cataract extraction.43 In the case of previous corneal incision surgery, the most suitable site in which to perform corneal incisions for cataract surgery must be carefully selected. The reason for this is to avoid dehiscence of the radial incisions and to avoid negatively changing the patient’s postoperative astigmatism. The sudden injection of viscoelastic substance can cause particularly deep radial incisions to open.44 If ocular herpes or uveitis episodes are in the patient’s medical history, the surgeon can focus his or her attention on analyzing the cornea and the anterior segment with the aim of noticing synechiae or alterations that might require special attention during cataract surgery. Sometimes patients who have frequent herpetic episodes are advised to have a vaccination before surgery with the aim of reducing

the risk of a postoperative herpes episode or they are given a general antiviral therapy. The presence of a phakic artificial lens in the anterior or posterior chamber will require a few specific steps to remove the lens before performing cataract surgery (Figure 3-10). Patients who have previously had retinal detachment or surgery for retinal detachment with vitrectomy or bands must be given an in-depth examination of the posterior segment to assess the possibility of relapse or of buffering substances in the vitreous chamber if there is no vitreous. In these situations, cataract surgery may be more difficult to perform and can influence the choice of viscoelastic substance to use with the aim of making the anterior chamber more stable during surgery. If the patient has previously undergone vitrectomy for retinal detachment, it is crucially important to know which buffering substances were used during the procedure and if there is any residual PoliDiMetiloSano (PDMS) (silicone oil) or if PDMS has been exchanged with BSS. The presence of PDMS can cause an increase in intraocular pressure during cataract surgery because the mechanical “collisions” induced by the ultrasound probe can cause an emulsion in the silicone oil, making it very mobile in the anterior chamber. The micro-bubbles formed in this way can occlude the pores of the trabecular meshwork, which causes intraocular pressure to rise. It is therefore important during aspiration of the viscoelastic substance (after introduction of the artificial lens) to clean the anterior chamber well in order to remove any residual oil bubbles. Cataract removal may be hindered during phacoemulsification. In the presence of PDMS, the posterior opacity of the lens is particularly marked and the lens sometimes adheres tightly to the posterior capsule. Finally, it is necessary to consider the presence of PDMS when performing the calculation of the artificial IOL to implant because the density of the silicone oil

22  Chapter 3 may make the measurement of the vitreous chamber (and therefore of biometry) inaccurate. Some authors consider the IOLMaster (Carl Zeiss Meditech AG) the most accurate instrument for this kind of measurement, and more accurate than the A-scan.45 In patients who have previously undergone vitrectomy and have had the silicone oil removed, the eye will be hypotonic, so cataract fragmentation and aspiration procedures must be performed with considerable caution to avoid zonular detachment, capsular tears, or repercussions on the retina. During the hydration of incisions, the surgeon must take into account the relative hypotony of the eye in order to avoid injecting an excessive amount of fluid in the anterior chamber, causing hypertension. Finally, when dealing with patients suffering from agerelated maculopathy,46 the time of onset of the retinal pathology and its extension and severity must be documented because it has occasionally been reported that retinal pathology may be worsened after cataract surgery.47 Furthermore, the time of onset, extension, and severity of disease are important prognostic indexes, especially in patients who have previously had photodynamic therapy, argon laser treatment, or injections of anti-VEGF drugs. This event has been reported (although no real cause was discovered) even in cases in which surgery was executed perfectly, with no trauma of any kind (ie, retinal pathology progressed, and one of the consequences was a decrease in visual acuity).

REFERENCES 1.

2.

3. 4. 5.

6.

7.

8. 9.

Lamoureux EL, Fenwick E, Pesudovs K, Tan D. The impact of cataract surgery on quality of life. Curr Opin Ophthalmol. 2011;22(1):19-27. Landers J, Goggin M. Ocular preference following implantation of aspheric and spherical intraocular lenses: an intra-individual comparison. Clin Exp Optom. 2010;93(6):419-425. Khan A, Conley A. An explanation for patient intraocular instrument visualization. J Cataract Refract Surg. 2005;31(1):237-238. Caird FI, Hutchinson M, Pirie S. Cataract and diabetes. Br Med J. 1964;(2):665-668. Drel VR, Pacher P, Ali TK, et al. Aldose reductase inhibitor fidarestat counteracts diabetes-associated cataract formation, retinal oxidative-nitrosative stress, glial activation, and apoptosis. Int J Mol Med. 2008;21(6): 667-676. Gothwal VK, Wright TA, Lamoureux EL, Pesudovs K. Visual Activities Questionnaire: assessment of subscale validity for cataract surgery outcomes. J Cataract Refract Surg. 2009;35(11): 1961-1969. de Fine Olivarius N, Siersma V, Almind GJ, Nielsen NV. Prevalence and progression of visual impairment in patients newly diagnosed with clinical type 2 diabetes: a 6-year follow up study. BMC Public Health. 2011;11:80. Pollreisz A, Schmidt-Erfurth U. Diabetic cataract—pathogenesis, epidemiology and treatment. J Ophthalmol. 2010;2010:608751. Dedov I, Maslova O, Suntsov Y, Bolotskaia L, Milenkaia T, Besmertnaia L. Prevalence of diabetic retinopathy and cataract in adult patients with type 1 and type 2 diabetes in Russia. Rev Diabet Stud. 2009;6(2):124-129.

10. Hartnett ME, Tinkham N, Paynter L, et al. Aqueous VEGF as a predictor of macular thickening following cataract surgery in patients with diabetes mellitus. Am J Ophthalmol. 2009;148(6): 895-901. 11. Kim SI, Kim SJ. Prevalence and risk factors for cataracts in persons with type 2 diabetes mellitus. Korean J Ophthalmol. 2006;20(4):201-204. 12. Glynn RJ, Rosner B, Christen WG. Evaluation of risk factors for cataract types in a competing risks framework ophthalmic epidemiol. Ophthalmic Epidemiol. 2009;16(2): 98-106. 13. Lira RP, Nascimento MA, Arieta CE, Duarte LE, Hirata FE, Nadruz W. Incidence of preoperative high blood pressure in cataract surgery among hypertensive and normotensive patients. Indian J Ophthalmol. 2010;58(6):493-495. 14. Gani J, Perlis N, Radomski SB. Urologic medications and ophthalmologic side effects: a review. Can Urol Assoc J. 2012;6(1):53-58. 15. Flach AJ. Intraoperative floppy iris syndrome: pathophysiology, prevention, and treatment. Trans Am Ophthalmol Soc. 2009;107:234-239. 16. Gupta A, Srinivasan R. Floppy iris syndrome with oral imipramine: a case series. Indian J Ophthalmol. 2012;60(2):136-138. 17. Handzel DM, Briesen S, Rausch S, Kälble T. Cataract surgery in patients taking alpha-1 antagonists: know the risks, avoid the complications. Dtsch Arztebl Int. 2012;109(21):379-384. 18. Bahar I, Kaiserman I, Rootman D. Cionni endocapsular ring implantation in Marfan’s syndrome. Br J Ophthalmol. 2007; 91(11):1477-1480. 19. Tham CC, Kwong YY, Baig N, Leung DY, Li FC, Lam DS. Phacoemulsification versus trabeculectomy in medically uncontrolled chronic angle-closure glaucoma without cataract. Ophthalmology. 2013;120(1):62-67. 20. Su PF, Lo AY, Hu CY, Chang SW. Anterior chamber depth measurement in phakic and pseudophakic eyes. Optom Vis Sci. 2008;85(12):1193-1200. 21. Vryonis N, Nikita E, Vergados I, Theodossiadis P, Filippopoulos T. Anterior chamber morphology before and after laser peripheral iridotomy determined by Scheimpflug technology in white patients with narrow angles. J Glaucoma. 2012. 22. Kameda T, Inoue T, Inatani M, Tanihara H; Japanese PhacoGoniosynechialysis Multicenter Study Group. Long-term efficacy of goniosynechialysis combined with phacoemulsification for primary angle closure. Graefes Arch Clin Exp Ophthalmol. 2013;251(3):825-830. 23. Eslami Y, Latifi G, Moghimi S, et al. Effect of adjunctive viscogonioplasty on drainage angle status in cataract surgery: a randomized clinical trial. Clin Experiment Ophthalmol. 2013;41(4):368378. 24. Tang Y, Qian S, Wang J, et al. Effects of combined phacoemulsification and viscogoniosynechialysis versus trabeculectomy in patients with primary angle-closure glaucoma and coexisting cataract. Ophthalmologica. 2012;228(3):167-173. 25. Latifi G, Moghimi S, Eslami Y, Fakhraie G, Zarei R, Lin S. Effect of phacoemulsification on drainage angle status in angle closure eyes with or without extensive peripheral anterior synechiae. Eur J Ophthalmol. 2012:0. 26. Kanthan GL, Mitchell P, Burlutsky G, Rochtchina E, Wang JJ. Pseudoexfoliation syndrome and the long-term incidence of cataract and cataract surgery: the Blue Mountains eye study. Am J Ophthalmol. 2013;155(1):83-88. 27. Scharfenberg E, Schlötzer-Schrehardt U. PEX syndrome. Clinical diagnosis and systemic manifestations. Ophthalmologe. 2012;109(10):952-961. 28. Belovay GW, Naqi A, Chan BJ, Rateb M, Ahmed II. Using multiple trabecular micro-bypass stents in cataract patients to treat openangle glaucoma. J Cataract Refract Surg. 2012;38(11):1911-1917.

Patient Selection  23 29. Ramsey E, Ramsey BL III, Childers J. Floppy iris syndrome: a drugrelated complication of cataract surgery. JAAPA. 2012;25(5):37-38, 41. 30. Kocabora MS, Gulkilik G, Yilmazli C, Taskapili M, Kucuksahin H, Doyduk-Kocabora A. The preventive effect of capsular tension ring in phacoemulsification of senile cataracts with pseudoexfoliation. Ann Ophthalmol (Skokie). 2007;39(1):37-40. 31. Park HY, Ahn MD. Cases of pseudophakic pseudoexfoliation in glaucoma patients. Korean J Ophthalmol. 2012;26(5):402-405. 32. González-Guijarro JJ, Tamés Haye I, Valdivia Pérez A. Phacoemulsification and acrylic intraocular lens in uveitis: a comparative study. Arch Soc Esp Oftalmol. 2012;87(1):9-16. 33. Suelves AM, Kruh JN, Aznar-Peña I, Siddique SS, Foster CS. Long-term safety and visual outcomes of anterior chamber intraocular lens implantation in patients with a history of chronic uveitis. J Cataract Refract Surg. 2012;38(10):1777-1782. 34. Liu W, Li D, Liu A, Xing X, Zhao S, Ji J. Pentacam-aided diagnosis of traumatic lens subluxation. J Trauma Acute Care Surg. 2012;72(3):E112. 35. Jung SH, Han KE, Sgrignoli B, Kim TI, Lee HK, Kim EK. Intraocular lens power calculations for cataract surgery after phototherapeutic keratectomy in granular corneal dystrophy type 2. J Refract Surg. 2012;28(10):714-724. 36. Zhao Q, Li NY, Zhong XW. Determination of anterior segment changes with Pentacam after phacoemulsification in eyes with primary angle-closure glaucoma. Clin Experiment Ophthalmol. 2012;40(8):786-791. 37. Thebpatiphat N, Hammersmith KM, Rapuano CJ, Ayres BD, Cohen EJ. Cataract surgery in keratoconus. Eye Contact Lens. 2007;33(5):244-246. 38. Mattax JB, McCulley JP. The effect of standardized keratoplasty technique on IOL power calculation for the triple procedure. Acta Ophthalmol Suppl. 1989;192:24-29. 39. Gupta N, Ram J, Chaudhary M. AcrySof toric intraocular lens for post-keratoplasty astigmatism. Indian J Ophthalmol. 2012; 60(3):213-215.

40. Scorcia V, Lucisano A, Beltz J, Busin M. Combined Descemetstripping automated endothelial keratoplasty and phacoemulsification with toric intraocular lens implantation for treatment of failed penetrating keratoplasty with high regular astigmatism. J Cataract Refract Surg. 2012;38(4):716-719. 41. Canovas C, Abenza S, Alcon E, Villegas EA, Marin JM, Artal P. Effect of corneal aberrations on intraocular lens power calculations. J Cataract Refract Surg. 2012;38(8):1325-1332. 42. Javadi MA, Feizi S, Malekifar P. Intraocular lens power calculation after corneal refractive surgery. J Ophthalmic Vis Res. 2012; 7(1):10-16. 43. Tang M, Wang L, Koch DD, Li Y, Huang D. Intraocular lens power calculation after previous myopic laser vision correction based on corneal power measured by Fourier-domain optical coherence tomography. J Cataract Refract Surg. 2012;38(4):589-594. 44. Demill DL, Hsu M, Moshirfar M. Evaluation of the American Society of Cataract and Refractive Surgery intraocular lens calculator for eyes with prior radial keratotomy. Clin Ophthalmol. 2011;5:1243-1247. 45. Kunavisarut P, Poopattanakul P, Intarated C, Pathanapitoon K. Accuracy and reliability of IOL master and A-scan immersion biometry in silicone oil-filled eyes. Eye (Lond). 2012;26(10): 1344-1348. 46. Milani P, Raimondi G, Morale D, Scialdone A. Biomicroscopy versus optical coherence tomography screening of epiretinal membranes in patients undergoing cataract surgery. Retina. 2012;32(5):897-904. 47. Rohart C, Fajnkuchen F, Nghiem-Buffet S, Abitbol O, Badelon I, Chaine G. Cataract surgery and age-related maculopathy: benefits in terms of visual acuity and quality of life—a prospective study. J Fr Ophtalmol. 2008;31(6, Pt 1):571-577.

4 Eye Examination and Presurgery Examination Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD The preoperative eye examination, which is crucially important for the execution of good cataract surgery without complications, can be divided into 3 steps—medical history, eye examination, and diagnostic procedures.

Finally, it is very useful to document any coexisting ocular pathology. It is important to document previous surgery or treatments performed on the cornea.

EYE EXAMINATION

MEDICAL HISTORY With regard to the collection of medical history data, it is useful to assess and document the conditions considered during the patient selection phase. Next, it is important that attention is focused on the cataract. The vision problems patients complain of can give the surgeon an idea regarding the density of the cataract and the kind of opacity. Halos around light sources, for example, are indicative of opacity in the cortical area of the lens, whereas very out-of-focus vision and the feeling of “fog in front of my eyes” are suggestive of mainly nuclear opacity. It is a good idea to assess the time of onset of the cataract and to know if vision deterioration was slow and gradual or if it arose suddenly. A sudden loss of vision can sometimes be associated with a traumatic cataract, especially if unilateral, so it is advisable to determine if the patient has had direct or indirect traumas in the orbital region of the affected eye. If the cataract is traumatic, it is important to assess, during the slit lamp examination, the lens-supporting structures (ie, are they undamaged), the position of the lens, and the angle (to check for size anomalies) (Figure 4-1). In the presence of a subluxated lens, the use of a capsular tension ring is advisable. It is also advisable to consider implanting the artificial lens in the sulcus or use scleral or iris suspension instead of implanting it in the bag.

During the eye examination, all ocular structures are examined (not just the cataract).1 The ocular adnexae are examined first, beginning with the eyelids, and any existing asymmetry, the presence of infections or inflammation (blepharitis or eczema) of the eyelashes, and the edge of the eyelids are noted. It is very important to assess palpebral aperture, especially in patients with particularly deep-set eyes or with eyelid edema.2 Alterations in the edge of the eyelids or conditions that cause altered palpebral occlusion require the use of artificial tears. It can also be useful to close the eyelids with special methods at night, in order to avoid deepithelization or ulceration of the cornea, which delays the healing of the surgical incisions. In some cases, it may be necessary to probe the lacrimal ducts, especially if, upon exerting pressure with fingers on the lacrimal sac, the secretion of material is observed, in order to exclude that they are totally or partially obstructed or if they are currently inflamed or infected. Infection in the lacrimal ducts must be treated with specific antibiotic and anti-inflammatory therapy before surgery. The proper eye examination is performed mainly with a slit lamp—a simple, widely used instrument that provides a complete view of all ocular structures (Figure 4-2).

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Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 25-33). © 2014 SLACK Incorporated.

26  Chapter 4

Figure 4-1. Traumatic cataract: The result of a perforating wound of the cornea, which caused iris adherence, is clearly visible.

Figure 4-3. Slit lamp examination of a corneal opacity, the result of a previous corneal ulcer.

The examination includes the inspection of the conjunctival fornix and the conjunctiva to document the presence of inflammation, infection, or scars resulting from previous trauma. The cornea is examined using, among other things, some colored filters of the slit lamp that enable the surgeon to check the transparency of the cornea and, if present, the site, extension, and depth of corneal opacities (Figure 4-3). The presence of pigment on the corneal endothelium is sometimes correlated to certain kinds of ocular intraocular pressure (IOP), whereas cotton-like or whitish exudates are a sign of previous uveitis episodes. The outcomes of refractive surgery or incisional surgery and the presence of keratoplasty must be documented, as they can significantly affect the operation and the intraocular lens power calculation. The presence of a cornea with endothelial dystrophy (guttae), other than delaying the patient’s recovery of vision after surgery requires the use (and/or repeated injection) of particularly dispersive viscoelastic substances to reduce

Figure 4-2. Patient at the slit lamp: The inclination of the light beam makes examining the eye easier and can be used to assess the depth of the anterior chamber.

intraoperative micro trauma, which this fragile cornea is very sensitive to. It is important to know about this condition because—like so many other clinical conditions—it must be included in the informed consent.3 If endotheliopathy is present, a special surgical technique is required, with a double injection of viscoelastic material. The first viscoelastic substance to be injected must be adhesive or dispersive4; that is, it must be a viscoelastic substance made of low molecular-weight molecules because they adhere well to tissues (in this specific case to the corneal endothelium, protecting it against potential damage). The second viscoelastic substance to be injected must be cohesive, that is, have high molecular weight and therefore be able to increase the space inside the ocular structures and keep the space stable during the maneuvers and manipulations of the surgical instruments.5 It is also very important to plan a surgical technique that does not use ultrasound much during the phacoemulsification and possibly to consider a chop or stop and chop technique.6 The anterior segment must be examined in great detail. To begin with, the width, depth, and content of the anterior chamber must be assessed and the presence of cells and inflammatory material must be excluded. The depth of the anterior chamber must be normal. If the anterior chamber is too shallow, insertion of the tip of the phaco handpiece can be difficult. Another problem is that the surgical instruments can accidentally touch the eye tissues and damage them (Figure 4-4). If the anterior chamber is too deep, the main difficulty is in the correct positioning of the instruments and the phaco probe. The probe must be held vertically to fragment the lens nucleus, which means there is stress on the tunnel and sudden fluctuations of the chamber caused by the possible, rapid loss of sealing capacity of the tunnel (Figures 4-5 and 4-6). Lastly, a very deep anterior chamber forces the surgeon to continuously adjust the focus and the magnification of the image of the operating field.

Eye Examination and Presurgery Examination  27

Figure 4-4. Image of a shallow chamber in a hyperopic patient.

Figure 4-5. Image of a deep anterior chamber in a patient with severe myopia. The phaco handpiece must be kept almost vertical to perform phacoemulsification without damaging the surrounding tissues.

Figure 4-6. Correct position of the U/S tip in an eye with an anterior chamber with normal depth.

Essentially, the analysis of the appearance and size of the anterior chamber is a crucial step in patient assessment because, depending on the clinical conditions, the surgeon can adjust the surgical procedure; for example, the height of the bottle can be changed during phacoemulsification, or only the side-port incisions can be made and capsulorrhexis can be performed before opening the main incision (in this way, the chances of the anterior chamber shallowing—with damage to other ocular tissues—are lower). Next, the pupillary margin should be examined to document any irregularities or indirect signs of a previous acute glaucoma attack. By reducing and increasing the diameter of the slit in the slit lamp, it is possible to study pupillary movements and to check for anomalies in the diameter and shape of the pupil and for adherences between the pupillary edge and the anterior capsule of the lens (Figure 4-7). The assessment of the iris tissue is focused on the color, the more or less spongy appearance, and the concave or convex shape of the iris surface. A convex iris can be a sign of increased IOP or of a hyperopic eye with a shallow anterior chamber, whereas

Figure 4-7. Eye with amber cataract and coloboma of the iris.

a flat iris is more often an indication of a myopic eye with a very deep anterior chamber. The presence of newly formed blood vessels on the pupillary edge or in the iris tissue are indications of retinal vascular pathology at an advanced stage, for example, very severe vein occlusion or diabetic retinopathy. The lens is analyzed in conditions of pharmacologic miosis and mydriasis (Figure 4-8). Attention is focused on the site of the lens, on its shape, level of opacity, and its contact with the neighboring eye structures. The presence of exfoliated cells on the anterior surface of the lens allows surgeons to diagnose pseudoexfoliation syndrome (Figure 4-9), whereas the presence of pigment on the

28  Chapter 4

Figure 4-8. Slit lamp examination of the crystalline lens.

Figure 4-10. Visante examination, showing the outcome of YAG laser iridotomy in a patient with a pathologically narrow sclerocorneal angle.

posterior surface of the lens can be caused by a possible, recent peripheral retinal break. The diagnosis of these last two conditions is very important to perform cataract surgery, thus reducing the risk of complications. In the case of an eye with pseudoexfoliation syndrome, in which the tissues supporting the lens are likely to be fragile, a viscoelastic substance (VES) with high molecular weight should be used in order to perform capsulorrhexis in a safe, controlled manner. Hydrodissection should be delicate to avoid traction on the tissues supporting the lens. On the contrary, in the case of a suspected peripheral retinal break, the periphery of the retina should be accurately examined in fine detail, possibly performing argon laser treatment before cataract surgery to strengthen the retinal areas at highest risk. The examination with mydriasis is useful to assess the amount of dilation. If the eye has poor mydriasis, extra arrangements—such as the use of dilating hooks, a dye to make capsulorrhexis easier, and addition of adrenaline to the BSS used during phacoemulsification—can be planned.

Figure 4-9. Eye with pseudoexfoliation syndrome. The flaking cells of the anterior capsule of the lens deposit on the margin of the pupillary edge.

A gonioscope or a Goldmann three-mirror lens is used to analyze the sclerocorneal angle and to assess its width, the presence of structural anomalies, or the presence of synechiae or neovascularization. After dilating the pupil, the vitreous chamber and the retina are examined using a Goldmann lens (or other magnifying lenses) (Figure 4-10). Mydriasis is better at examining the size of the cataract; the kind of opacity; the shape, dimension, and position of the lens; and lens luxation (if any). It often allows doctors to document laxity of the zonules. The examination of the vitreous chamber must exclude the presence of inflammation or traction on the retina and assess the presence of vitreous floaters and retinal detachment (if any). The inspection of the posterior pole and the optic disc can exclude the presence of increased ocular pressure, vascular or degenerative disease, and the presence of retinal tears (or lesions that may progress to tears). Regarding the macula, the presence of alterations, such as cellophane maculopathy or macular pucker and signs of senile macular degenerations, in a more or less advanced phase, must be assessed. The least conditions can compromise the final result of cataract surgery because there may be very limited recovery of vision. Finally, in the case of alterations of the posterior pole and the optic nerve, specific diagnostic procedures (such as optical coherence tomography [OCT], visual field, and Heidelberg retina tomography) should be performed before cataract surgery to determine the amount of retinal tissues damage.

DIAGNOSTIC PROCEDURES Today, ophthalmologists have a broad range of instruments that allow them to assess and study the eyes of their patients.

Eye Examination and Presurgery Examination  29

Figure 4-11. Noncontact tonometry provides the value of IOP without touching the eye. It is very useful when dealing with poorly cooperative patients or after surgery to reduce the contact between instruments and the eye that has just been operated on.

Diagnostic procedures are generally performed in a specific sequence during the eye examination. Auto refraction is the first test and is performed when the opacity of the lens is not marked.7 It is used to measure keratometric indexes and to estimate the refractive error of the patient’s eyes.8 Auto refraction is quick and easy, and there is no contact with the patient’s eye.9 It is good practice to examine the eye that is to be operated and the contralateral eye to check for anisometropia. This examination also provides indirect information on the clinical condition of the eye that needs operation; for example, if measuring the refractive error is not possible, there may be a very dense cataract, extensive corneal opacity, or poor visual fixation. Likewise, very high levels of myopia (that do not match the strength of the patient’s glasses) can be an indication of a cataract in an advanced stage. Auto refraction is followed by noncontact tonometry, which supplies a quite precise estimate of the patient’s IOP (Figure 4-11). If the measured values are outside the normal range, applanation tonometry (Figure 4-12) is performed— but keratometry, topography, and Schirmer test must be performed first because applanation tonometry alters their results. Visual acuity is performed with best corrected lenses on frames or with a phoropter. Measuring preoperative visual acuity is important because it closely correlates with the level of opacity of the lens and with the health of all intraocular structures. It is important to measure near vision and distance vision—myopia in a previously hyperopic patient, associated with improved uncorrected visual acuity for near, is an indication that the cataract is mainly nuclear. On the contrary, poor distance vision, even with correction, suggests the presence of a dense cataract. It is also useful to carefully assess the patient’s residual accommodation capacity if planning to implant an accommodative artificial

Figure 4-12. Applanation tonometry after instilling a drop of anesthetic solution: The lacrimal film is colored with fluorescein and applanation is performed with the tonometer.

lens. During the reading test, it can be useful to perform an Amsler test as well, which identifies problems in the macula. The corneal surface is studied using instruments such as manual keratometers, corneal topographers, aberrometers, specular microscopes, and pachymeters. Keratometry is the measurement of astigmatism on the two main axes of the cornea. It provides an indication of where to perform the main and accessory incisions during surgery (as corneal incisions can reduce preoperative astigmatism).10 Furthermore, by marking the main axis of astigmatism, relaxing incisions can be performed at the end of the surgical procedure. Determining astigmatism is also useful if planning to implant a toric lens, as it is necessary for the lens-related calculation and to determine the position of the artificial lens in relation to the main axes (0 to 90 to 180 degrees). Corneal topography gives a map of the anterior surface of the cornea, revealing irregular areas or deformities. This technique also shows if refractive or incisional surgery was previously performed and if there are induced deformations caused, for example, by the prolonged use of contact lenses. This should be considered in association with astigmatism and myopia values that are higher than those reported in the patient’s medical history because they could be artifacts that can make the calculation related to the artificial lens to be implanted less precise. Preoperative topography can be used to check for the presence of irregular astigmatism and to confirm the possibility of form fruste keratoconus. This condition may cause the surgeon to consider the possibility of implanting a toric artificial lens that partly reduces astigmatism. However, for this to be done, the surgeon must be relatively sure the condition has been stable for the past few years and that there is sufficient symmetry. This can be considered because patients with cataracts usually are of an age when keratoconus is generally stable (Figure 4-13).

30  Chapter 4

Figure 4-13. Topography of keratoconus.

Figure 4-15. Examination of normal endothelium.

Aberrometry is used to study the errors and aberrations of the eye.11 The optical aberrations of the eye are unique and are significantly dependent on pupillary size. Aberrometer emits a laser beam that, on entering the eye, is reflected. How it is reflected depends on the retinal surface, the vitreous, the lens, the posterior surface of the cornea, and especially the anterior surface of the cornea. The reflection of the light in the eye creates a wavefront, which is analyzed to establish the errors and defects of the eye that negatively affect the patient’s quality of vision. In the case of specific aberrometry values, latest-generation artificial lenses, which correct aberrations as well, can be chosen. To this end, only corneal aberrations are to be considered (Figure 4-14). Specular microscopy is the acquisition of a photograph of the layer of endothelial cells in the cornea. This test also measures the thickness of the cornea. The shape, number, and layout of corneal cells can be studied with the obtained image. In some pathological conditions, there is a reduction in the number of corneal cells, which leads to changes in their size and shape. In the most serious cases of corneal dystrophy, bubbles occur in the corneal epithelium, which can cause corneal opacity severe enough to hinder the surgeon (Figures 4-15 and 4-16).

Figure 4-14. Aberrometry.

Figure 4-16. Pathological endothelium: The patient is suffering from corneal guttata.

The health of the corneal endothelium has a significant impact on cataract surgery. If endothelial dystrophy is not severe and is in the early stages, a viscoelastic substance that adequately protects corneal cells (using the double injection technique) should be chosen. If endothelial dystrophy is

Eye Examination and Presurgery Examination  31

Figure 4-18. Visante OCT examination: This procedure requires a few minutes and does not affect the patient, who is asked to look at a light source. There are different acquisition patterns that depend on the eye region to be examined and the condition to be evaluated; for example, there are patterns to study the angle in patients with glaucoma. Figure 4-17. Example of a printout of an examination with a dynamic pupillometer. The behavior of the pupil in photopic and mesopic conditions and the time of adjustment to light and darkness are very important data to consider when choosing an artificial multifocal lens.

severe, it can be difficult to see the lens capsule clearly during capsulorrhexis because of corneal opacity. In this case, coloring the anterior capsule with trypan blue dye before capsulorrhexis should be considered. A more or less severe corneal dystrophy affects postoperative vision recovery and postoperative patient management because patients will take longer to recover and there is a risk of corneal edema. Patients must be informed—in a clear, understandable way—about the poor condition of the endothelium, which must also be mentioned in the informed consent form (which must include possible consequences of poor visual recovery). Static and dynamic pupillometry are two tests performed after stimulating the patient’s eye with light sources of different intensity and in situations with different environmental illumination. A dynamic pupillometer can also be used to perform a dynamic study of the reflex pupillary dilation process. This information is particularly important for surgeons who have to decide on the lens most suitable for each patient. The new, now commonly available, artificial lenses, such as multifocal and aspheric lenses, require a detailed study of pupillary dynamics because these lenses must be implanted in eyes with very specific characteristics to guarantee the best performance (Figure 4-17). Contact pachymetry is useful because it supplies important information on corneal thickness, especially in the presence of corneal alterations. The presence of thinner areas in the cornea can affect the final refractive result, whereas the presence of increased corneal thickness is a possible indication of endothelial distress.

The OCT device for the anterior segment—which has Visante as its “founding father”—can supply a lot of information on the anterior segment12 (Figure 4-18). To begin with, OCT provides a complete image of the anterior segment, which makes it possible to assess the corneal surface and analyze shape, regularity, transparency, and symmetry of the segment, as well as measure its thickness in every point.13 OCT examines the anterior chamber and its contents and provides its depth and width. It measures the sclerocorneal angle and examines the anterior surface of the iris and lens, allowing surgeons to note if there are asymmetries in the site and position of the lens and the presence of adhesions. The identification of a particularly curved iris and a reduction in the sclerocorneal angle can be taken into consideration when establishing which kind of viscoelastic substance is most suitable. The viscoelastic substance should increase the intraocular area in which surgery is performed, as well as stabilize the anterior chamber and reduce the risk of a sudden increase in pressure. The IOLMaster allows measurement of the length of the eye in the anterior–posterior axis. It is a quick, nocontact examination that requires little cooperation from the patient. As well as measuring the length of the eye (ultrasound biometry),14 the IOLMaster automatically calculates the value of the lens to be implanted.15 However, this instrument is not able to perform an accurate measurement when the cornea or lens has a severe opacity. The data obtained by the IOLMaster can be compared with that of ultrasound biometry in order to obtain a very precise value of the power of the lens. The instrument also measures the depth of the anterior chamber and the white-to-white measurement (Figure 4-19).

32  Chapter 4

Figure 4-19. IOLMaster 500 (Carl Zeiss Meditech AG): The patient is asked to look at a light and the instrument acquires the length of the eye, the white-to-white dimension, and keratometric values. The calculation for the artificial lens is then made.

Ultrasound biometry is the measurement of the eye’s length. This value can be obtained by using two different kinds of probes—one needs to touch the corneal surface and uses an optical system to measure the eye’s length, whereas the other uses an immersion device that measures the eye’s length without direct contact. In both cases, the final value is an average of about 10 successive measurements (the examination is repeated to obtain a precise measurement). The optical biometer can perform the calculation of the intraocular lens to implant. Other than measuring the length of the eye, the same A-scan probe can be used to measure the lens and the anterior chamber and therefore can help demonstrate a reduced depth of the anterior chamber or the presence of a particularly round lens (Figure 4-20). An ultrasound B scan is very useful preoperatively, especially in the case of very dense cataracts, which makes direct inspection of the ocular fundus difficult. The site of the lens and its interaction with the vitreous body and vitreous chamber can be assessed with an ultrasound scan, which also reveals if there is posterior or peripheral lifting of the retina and retinal detachment. Finally, an ultrasound scan can be used to check for the presence of blood or inflammatory material in the vitreous chamber. Fluorescein angiography and dynamic indocyanine green angiography are two tests used to study retinal vascularization. The presence of vascular retinopathies—and their severity and progress—can be checked with these tests, which can also be used to evaluate macular degeneration that can negatively affect recovery of vision after surgery. In general, angiography tests are performed if there are doubts about the condition of the macula, especially if the patient’s visual acuity is reduced and the cataract is not particularly dense (Figure 4-21).

Figure 4-20. Ultrasound biometry—immersion technique: Contact with the eye may make this examination a little difficult in poorly cooperative patients.

OCT is a retinal examination with a technique that is reproducible, noninvasive and painless for the patient and supplies a lot of information about the condition of the patient’s retina. It can be used to study and measure macular thickness. Preoperatively, it is useful to evaluate patients with poor visual acuity associated with minimal opacity of the lens and patients with high myopia who often have a cleft in the posterior pole. Postoperatively, OCT can be used to check for the presence of intraretinal fluid in the macula and to diagnose the Irvine-Gass syndrome and other pathologies of the posterior pole. It can also be used to compare, over time, the effectiveness of an intraretinal treatment and to document the progression of a pathological process (Figure 4-22). Ophthalmologists can choose from a broad range of diagnostic procedures that can all be used to gather substantial information on the cataract eye, in order to diagnose any concomitant pathologies at an early stage and to perform surgery safely.

Eye Examination and Presurgery Examination  33

Figure 4-21. Angiography is performed to gain more information on the patient. It is preceded by the examination of the ocular fundus, if retinal pathology is suspected or found.

REFERENCES 1.

2.

3.

4.

5.

6.

7.

Gothwal VK, Wright TA, Lamoureux EL, Pesudovs K. Using Rasch analysis to revisit the validity of the Cataract TyPE Spec instrument for measuring cataract surgery outcomes. J Cataract Refract Surg. 2009;35(9):1509-1517. Lee H, Chung JL, Kim EK, Sgrignoli B, Kim TI. Univariate and bivariate polar value analysis of corneal astigmatism measurements obtained with 6 instruments. J Cataract Refract Surg. 2012;38(9):1608-1615. DeMill DL, Zaugg BE, Pettey JH, et al. Objective comparison of 4 nonlongitudinal ultrasound modalities regarding efficiency and chatter. J Cataract Refract Surg. 2012;38(6):1065-1071. Moschos MM, Chatziralli IP, Sergentanis TN. Viscoat versus Visthesia during phacoemulsification cataract surgery: corneal and foveal changes. BMC Ophthalmol. 2011;11:9. Rosado-Adames N, Afshari NA. The changing fate of the corneal endothelium in cataract surgery [Review]. Curr Opin Ophthalmol. 2012;23(1):3-6. Faramarzi A, Javadi MA, Karimian F, et al. Corneal endothelial cell loss during phacoemulsification: bevel-up versus bevel-down phaco tip. J Cataract Refract Surg. 2011;37(11):1971-1976. de Juan V, Herreras JM, Martin R, et al. Repeatability and agreement of ARK-30 autorefraction after cataract surgery. Clin Exp Ophthalmol. 2012;40(2):134-140.

Figure 4-22. OCT/SLO examination—a noninvasive, rapidly executed test that provides a lot of information on the condition of retinal health. 8.

9.

10.

11.

12.

13.

14.

15.

Buckhurst PJ, Wolffsohn JS, Shah S, Naroo SA, Davies LN, Berrow EJ. A new optical low coherence reflectometry device for ocular biometry in cataract patients. Br J Ophthalmol. 2009;93(7): 949-953. Leccisotti A. Intraocular lens calculation by intraoperative autorefraction in myopic eyes. Graefes Arch Clin Exp Ophthalmol. 2008;246(5):729-733. Potvin R, Hill W. New algorithm for post-radial keratotomy intraocular lens power calculations based on rotating Scheimpflug camera data. J Cataract Refract Surg. 2013;39(3):358-365. Mencucci R, Giordano C, Favuzza E, Gicquel JJ, Spadea L, Menchini U. Astigmatism correction with toric intraocular lenses: wavefront aberrometry and quality of life. Br J Ophthalmol. 2013;97(5): 578-582. Leng T, Lujan BJ, Yoo SH, Wang J. Three-dimensional spectral domain optical coherence tomography of a clear corneal cataract incision. Ophthalmic Surg Lasers Imaging. 2008;39 (4 Suppl):S132-S134. Kaluzny BJ, Szkulmowska A, Kaluzny JJ, et al. In vivo imaging of posterior capsule opacification using spectral optical coherence tomography. J Cataract Refract Surg. 2006;32(11):1892-1895. Simsek A, Ciftci S. Evaluation of ultrasonic biomicroscopy results in anterior eye segment before and after cataract surgery. Clin Ophthalmol. 2012;6:1931-1934. Bhatt AB, Schefler AC, Feuer WJ, Yoo SH, Murray TG. Comparison of predictions made by the intraocular lens master and ultrasound biometry. Arch Ophthalmol. 2008;126(7):929-933.

5 Hardness of the Nucleus Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD The hardness of the nucleus must be assessed to plan cataract surgery correctly.1 The degree of lens opacity determines which parameters of the phacoemulsification device are selected and the most suitable viscoelastic substance to use (the one that allows surgeons to perform the operation in the safest and most controlled manner). The hardness of the lens nucleus is assessed with a slit lamp after dilating the pupil well with pharmacological treatment. It is crucially important to see the outer regions of the lens as well in order to examine the cataract correctly. The hardness of the nucleus is, without doubt, related to the time and manner of opacity onset. An old cataract that causes considerable visual loss will certainly be much harder than a recently diagnosed one without remarkable subjective symptoms. A trauma-induced cataract operated on at an early stage will be softer than a lens that has become progressively cloudy over many years. Some aspects of the lens affected by opacity must be assessed to establish the cataract’s degree of hardness. Color and transparency—A transparent nucleus has a soft, gelatinous consistency. In this case, especially if the patient is young, ultrasound is not required to remove it. An aspiration probe with a 0.5-mm (approximately) opening is enough.2 A semitransparent nucleus, with only a few areas of opacity, is a predominantly soft nucleus. In this case as well, sometimes an aspiration probe is enough or, if an ultrasound probe is used, low energy can be used for a short time. The hardness of milky, white, or yellow lens is higher, so an ultrasound probe is needed with increasingly higher power settings. The last case is that of an orange, almost brown, nucleus (amber cataract), which is very hard and requires significant ultrasound power. In these cases, surgeons usually resort to aggressive phacoemulsification

techniques, such as phaco-chop or stop-and-chop, in order to reduce ultrasound usage. A little more needs to be said on hypermature cataracts, in which the degeneration process is very advanced. In these conditions, there is extreme hardness of the nucleus, which has very dense areas. In this unusual situation, great care is required during the phacoemulsification phase because sometimes the capsule is fragile and often accidentally breaks, which leads to scattering of nucleus fragments in the anterior and vitreous chambers. The site of opacity: A human lens may have opacity in the center (nuclear cataract), peripherally along the equator (cortical cataract), or on the anterior capsule (anterior polar cataract) or posterior capsule (posterior polar cataract and posterior subcapsular cataract). In general, cortical cataracts appear softer and more gelatinous than nuclear or polar cataracts. The same applies to posterior subcapsular opacities, even if the cortical opacities of an old, complete cataract can be much harder.3

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●

●

●

The degree of visibility of the posterior capsule at the slit lamp examination: If the posterior capsule of the crystalline lens is clearly visible at the slit-lamp examination, the nucleus is not so hard. If it cannot be clearly seen, the cataract is complete and the degree of nucleus hardness is higher. The degree of visualization of the ocular fundus: If the posterior pole of the retina and the retinal periphery cannot be seen clearly, the cataract is very dense and almost always very hard. In these cases, an ultrasound B scan is required to assess any medical conditions of the ocular fundus.

Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 35-38). © 2014 SLACK Incorporated.

36  Chapter 5

Figure 5-1. Juvenile soft cataract.

Figure 5-2. Slightly hard cataract.

phaco probe can remove these soft cataracts without using ultrasound. Microscopic examination shows a very intense red reflex with marked luminosity in the entire pupillary field (Figure 5-1). ●

Figure 5-3. A moderately hard cataract.

There is also some indirect evidence that allows surgeons to assess the degree of hardness of the nucleus; for example, the fact that certain diagnostic procedures (such as refraction, the IOLMaster 500 [Carl Zeiss Meditech AG], or ultrasound biometry) cannot be performed is sometimes an indication of increased lens hardness. The Pentacam (Oculus Optikgerote GmbH) scan has two programs: Pentacam Lens Densitometry Program and Pentacam Nucleus Staging (to assess the degree of nuclear opacity), which can measure and assess the density of the lens and the degree of opacity. The chromatic appearance of the nucleus provided by slit lamp examination and the observation of the red reflex through a microscope allow surgeons to assess the best technique to remove cataracts. The hardness of the nucleus can be classified as follows: Grade 1 (soft nucleus): Transparent or pale grey, it is often associated with cortical or subcapsular opacity of recent onset, such as in presenile metabolic cataracts. Using the 0.5-mm aspiration probe alone and the ●

●

●

●

Grade 2 (slightly hard nucleus): Pale-gray or yellowishgray nuclear cataract. The nucleus usually has consistency even if it appears transparent. These are presenile cataracts, mainly posterior subcapsular cataracts. These nuclei offer little resistance to the phaco tip and accessory instruments such as spatulas and hooks. The red reflex is slightly reduced. Often in these cases, retroillumination is more marked in the more peripheral areas of the pupillary field and less intense in the center (Figure 5-2). Grade 3 (moderately hard nucleus): This is the typical nucleus of senile cataracts and appears yellow when the cataract is mainly nuclear and when the nucleus affects the peripheral areas of the lens as well. It is mainly gray when cataracts have a cortical-capsular element, especially in patients aged more than 60 years. Microscope examination reveals a red reflex so reduced that the pupillary area appears gray-brown (Figure 5-3). Grade 4 (hard nucleus): The color is yellow amber and it is found in advanced senile cataracts with an extensive nuclear area that has evolved over many years. In general, a long time is required to fragment these cataracts and higher quantities of ultrasound are needed to shatter them. Chop techniques are useful in these cases. There is almost no red reflex and retroillumination gives off a white-grayish color (Figure 5-4). Grade 5 (very hard nucleus): The color is brown, with tones ranging from amber to black. It is typical of hypermature cataracts. The nuclear consistency extends to the entire crystalline lens. These cataracts require high ultrasound intensity and often techniques other than phacoemulsification, such as fragmentation

Hardness of the Nucleus  37

Figure 5-4. Hard cataract.

Figure 5-5. Very hard cataract.

TABLE 5-1.

GRADE SCALE OF NUCLEUS HARDNESS Grade

Ultrasound Time

Color

Type of Cataract

Red Reflex

Grade 1

Minimal or none

Transparent or pale gray

Cortical or subcapsular, recent

High

Grade 2

Limited

Gray or gray-yellow

Posterior subcapsular

Marked

Grade 3

Medium

Yellow or yellow-gray

Nuclear, cortical-nuclear

Good

Grade 4

Long and phaco-chop

Yellow-amber or amber

Cortical-nuclear, dense

Scarce

Grade 5

Very long phacofragmentation technique or ECCE

Dark brown or blackish

Total, dense

None

Figure 5-6. Congenital anterior polar cataract.

with a chopper. Sometimes extracapsular cataract extraction (ECCE) with a large incision is required. There is no red reflex. In this case, it is always necessary to use vital dyes to highlight the structures of the lens, anterior capsule, cortex, and nucleus (Figure 5-5 and Table 5-1).

Figure 5-7. Congenital posterior polar cataract.

There are also some cases of congenital cataract with a very particular appearance. The opacity can be at the center of the anterior capsule (anterior polar capsule) (Figure 5-6) and, in other cases, on the posterior capsule (posterior polar capsule) (Figure 5-7). Some have a star-like appearance (Figure 5-8) or look like a Christmas tree (these are associated with metabolic disorders) (Figure 5-9).

38  Chapter 5

Figure 5-8. Star-shaped congenital cataract.

Figure 5-10. Images of the LOCS III classification system with which to compare the eye of the patient examined with a slit lamp. The top row has the standard NO and NC photographs. The second and third rows contain the standard images for grading C and P.

Figure 5-9. Christmas tree–shaped cataract.

opacity. Likewise, the degree of posterior subcapsular opacity (P) is determined through the comparison with photographs with increasing opacity. The degree of each analyzed feature is derived by locating the image of the patient’s lens on the scale of severity for each feature represented in terms of color transparency. NO and NC are graded on a decimal scale of 0.1 to 6.9, whereas the severity of cortical opacity (C) and posterior subcapsular opacity (P) are graded on a decimal scale of 0.1 to 5.9. The final grade on the LOCS III scale comprises four decimal values, 1 for each examined feature—NO, NC, C, and P5 (Figure 5-10).

REFERENCES 1.

Another system for the classification of lens opacity is the Lens Opacities Classification System III (LOCS III),4 which is acknowledged all over the world and was originated for the first time by Chaylack et al in 1993.6 This scientifically valid and widely used system is based on the comparison of photographs to establish the degree of lens opacity, the severity of the cataract, and its progress over time. Cataract classification is performed using a slit lamp. The degree of opacity is defined by the assessment of four characteristics, classified in three groups of photographs in which the degree of transparency progressively changes. The degree of nuclear opacity and brunescence is graded in six photographs. The diffusion of opacity in the nuclear region is defined nuclear opalescence (NO) and the intensity of brunescence is called nuclear color (NC). The severity of the cortical cataract (C) is defined by comparing cortical opacity (which takes on a spoke-like appearance) to five photographs depicting increasing amounts of

2.

3.

4.

5.

6.

Hou P, Hu YJ. Phacoemulsification of hard nucleus cataracts. J Cataract Refract Surg. 2010;36(5):872-873. Aslan L, Aksoy A, Aslankurt M, Ozdemir M. Lens capsule-related problems in patients undergoing phacoemulsification surgery. Clin Ophthalmol. 2013;7:511-514. Richter-Mueksch S, Sacu S, Weingessel B, Vécsei-Marlovits VP, Schmidt-Erfurth U. The influence of cortical, nuclear, subcortical posterior, and mixed cataract on the results of microperimetry. Eye (Lond). 2011;25(10):1317-1321. Tan AC, Wang JJ, Lamoureux EL, et al. Cataract prevalence varies substantially with assessment systems: comparison of clinical and photographic grading in a population-based study. Ophthalmic Epidemiol. 2011;18(4):164-170. Davison JA, Chylack LT. Clinical application of the Lens Opacities Classification System III in the performance of phacoemulsification. J Cataract Refract Surg. 2003;29(1):138-145. Chylack LT, Wolfe JK, Friend J, et al. Quantitating cataract and nuclear brunescence, the Harvard and LOCS systems. Optom Vis Sci. 1993;70(11):886-895.

6 The Pupil Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD It is crucially important to inspect the anterior segment and assess the position and shape of the pupil and pupillary reflexes in every eye. Eyes that have previously had an acute glaucoma attack can have a hyporeactive or atonic pupil, which causes fixed mydriasis; in these cases, intraoperative iridoplasty may have to be planned (to reduce postoperative photophobia). It is also important to consider that atonic or dystrophic iris tissue can make surgery more difficult because, during phacoemulsification and irrigation maneuvers, the tissue can billow considerably, touching the phaco or aspiration tip and causing damage to the iris or bleeding. It could also make the depth of the anterior chamber unstable, which makes surgical procedures more difficult.1 It is important to assess the size of the pupil, reactivity to light, and the presence of adhesions between the pupillary margin and the anterior capsule of the lens in patients who have a history of anterior uveitis episodes. In these conditions, during surgery, the surgeon may consider performing maneuvers to detach the adhesions and restore a certain amount of function to the pupillary sphincter if some muscle tone still exists (Figures 6-1 to 6-4). Finally, in eyes with traumatic cataracts, it is useful to analyze the function of the pupillary sphincter and the pupil site because sometimes, after a violent contusion trauma, the pupillary opening may move as a result of the detachment of some of the iris root.2 In these cases, it is important to know the original site of the pupil in order to center the optic of the artificial lens correctly. The iris root must also be sutured to reduce possible postoperative photophobia. Finally, special consideration is required when examining pupillary dynamics of patients being treated for

prostate-related conditions because it is well known that the drugs involved reduce the tone of the iris tissue and cause the pupil to be more resistant to pharmacological dilation. It is therefore useful to remember to use atropine to dilate the pupil before surgery and to add adrenaline to the balanced salt solution (BSS) during phacoemulsification. These two drugs can maintain good pupillary dilation, reducing the risk of complications and damage to ocular structures during surgery. With the use of the new “premium” artificial lenses (ie, accommodative, multifocal, and toric), the assessment of pupil size and the study of pupil dynamics are very important steps of the presurgery examination. Knowledge of pupillary dynamics is important when offering a patient the implantation of a multifocal lens. Some multifocal refractive lenses have strict light condition requirements to work properly, which means they are affected by pupillary dynamics.3 The particular geometric construction of the anterior surface of refractive multifocal artificial lenses has concentric annular zones with different curvature. They use the physical principle of refraction to create focal points for distance vision, intermediate vision, and near vision. A pupil with a large diameter (>7 to 8 mm) in conditions of poor illumination can create a blurred image with halos of distant objects, or halos surrounding point source light could be perceived. In these cases, it might be more suitable to implant a diffractive multifocal artificial lens. The anterior curvature of diffractive multifocal artificial lenses is used to correct the inability to have focal points in distance vision. The posterior surface has concentric rings with apodized steps that use the physical principle of diffraction to create a more anterior, second focal point for near vision. The particular geometry of

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40  Chapter 6

A

A

B

B

C

C

Figure 6-1. (A) Detachment of iris–lens synechiae. (B, C) The technique to release iris–lens synechiae is carried out by sliding an olive-tip spatula gently under the iris.

Figure 6-2. (A) Pupillary edge stretching maneuver. (B, C) A push–pull hook is used in the stretching maneuver. The instruments are made to slide perpendicularly so that pupillary synechiae are broken.

The Pupil  41

Figure 6-3. Cutting of fibers at the pupillary edge, to obtain a larger diameter of the pupillary opening.

Figure 6-4. Appearance of the pupil after making the incisions at the pupillary edge at 360 degrees.

MAIN FEATURES OF SOME TYPE OF MULTIFOCAL LENS Type of Multifocal Lens

Distance Vision

Intermediate Vision

Near Vision

Dependence on Pupil Diameter

Diffractive (Alcon AcrySof ReSTOR, AMO ZM900; Alcon)

Good

Poor

Good

No

Good

Fair (less than diffractive IOLS)

Yes

Fair (less than Refractive monofocal IOLS) AMO Array, AMO ReZoom, (Abbott Medical Optics) ZEISS AcryLisa (Carl Zeiss Meditec AG)

these artificial lenses makes them less sensitive to pupillary dynamics. The pupillary diameter must be measured in mesopic illumination conditions using a static pupillometer in order to obtain an estimate of the pupil’s maximum diameter.4 A dynamic pupillometer, which is used to study popular dynamics, employs light stimuli of different intensity that are used to register pupillary activity in real time. In this way, measurements of the pupil in miosis and mydriasis conditions are obtained, with a plot of the pupil’s reaction times to sudden light stimulation or conditions of darkness.

REFERENCES 1.

2.

3.

4.

Watanabe K, Negishi K, Dogru M, Yamaguchi T, Torii H, Tsubota K. Effect of pupil size on uncorrected visual acuity in pseudophakic eyes with astigmatism. J Refract Surg. 2013;29(1):25-29. Eom Y, Yoo E, Kang SY, Kim HM, Song JS. Change in efficiency of aspheric intraocular lenses based on pupil diameter. Am J Ophthalmol. 2013;155(3):492-498. Nagy ZZ, Filkorn T, Takács AI, et al. Anterior segment OCT imaging after femtosecond laser cataract surgery. J Refract Surg. 2013;29(2):110-112. DeCroos FC, Chow JH, Garg P, Sharma R, Bharti N, Boehlke CS. Analysis of resident-performed manual small incision cataract surgery (MSICS): an efficacious approach to mature cataracts. Int Ophthalmol. 2012;32(6):547-552.

7 Anesthesia Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD The anesthesia used depends on a number of factors but chiefly on the patient’s clinical conditions and on the surgeon’s experience.1 In the case of cataract surgery, the types of anesthesia used are topical, local (sub-Tenon block, peribulbar block, and retrobulbar block), and general (Table 7-1).2,3 General anesthetic is hardly ever used now and it is limited to certain situations when patients will not cooperate (children) or cooperation is unpredictable (such as very agitated patients or patients suffering from head tremors or neurological disorders5 that can negatively affect cooperation during surgery, or patients with mature cataracts that prevent visual fixation of the microscope light).6 Topical anesthesia with eye drops containing 4% lidocaine is used in most cases of cataract surgery performed with phacoemulsification.7 The anesthetic drops must be applied according to a precise schedule8 (ie, one drop about 20 minutes before surgery and another drop just before beginning the operation).9 Excessive 4% lidocaine can cause damage to the corneal epithelium and a temporary epithelial haze, which makes viewing intraocular structures more difficult. It is advisable to instill a drop of anesthetic in the contralateral eye as well to help the patient keep both eyes open during surgery.10 When using topical anesthesia,11 it is good practice to ask the patient to perform small eye movements before beginning the operation (in order to assess cooperation) and during some “neutral” phases of surgery (to reduce emotional tension).12 The surgeon may find it useful to

keep the eye still by using instruments such as a fixation ring, an olive-tip spatula, or corneal forceps. Finally, the speculum must be positioned in the most delicate way possible to avoid sudden voluntary contractions of the palpebral muscles. If the patient is a little agitated and not fully cooperative, sub-Tenon block may be performed by injecting a 1% lidocaine solution under Tenon capsule using a blunt, curved needle cannula. The procedure begins by instilling a few drops of 4% lidocaine or benoxinate in the conjunctival fornix, then making a small opening in the bulbar conjunctiva and Tenon capsule with blunt-tip microscissors. The anesthetic is then injected. Using the arched portion of the needle cannula, a light pressure is exerted on the conjunctiva to favor the diffusion of the anesthetic on the bulbar surface. In some cases, when the patient is not cooperative or has a very dense cataract that makes visual fixation impossible, it is preferable to proceed with local anesthesia via the peribulbar or retrobulbar injection of 0.5% marcaine without adrenaline and 2% carbocaine without adrenaline. The injection should be made about 30 to 40 minutes before surgery. Peribulbar and retrobulbar injections cause palpebral akinesia and globe akinesia as well, so intraoperative maneuvers are easier as the voluntary movements of the globe are limited.13 If one of these types of anesthesia is used, the operated eye must be bandaged at the end of surgery to avoid diplopia, as the effect of the anesthetic may last a few hours (Figure 7-1).

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44  Chapter 7

TABLE 7-1.

TYPES OF ANESTHESIA AND DRUG USED4 Administration Route

REFERENCES 1.

Drug Used 2.

Topical

4% lidocaine, single-dose drops

Sub-Tenon block

1% lidocaine, injectable solution

Peribulbar and retrobulbar block

0.5% marcaine without adrenaline, injectable solution + 2% carbocaine without adrenaline, injectable solution

3.

4.

5.

6. 7.

8.

9.

10.

11.

Figure 7-1. Injection points to obtain good immobility of the globe.

12.

13.

MacPherson R. Structured assessment tool to evaluate patient suitability for cataract surgery under local anaesthesia. Br J Anaesth. 2004;93(4):521-524. Ahmad N, Zahoor A, Motowa SA, Jastaneiah S, Riad W. Satisfaction level with topical versus peribulbar anesthesia experienced by same patient for phacoemulsification. Saudi J Anaesth. 2012;6(4):363-366. Lee RM, Foot B, Eke T. Posterior capsule rupture rate with akinetic and kinetic block anesthetic techniques. J Cataract Refract Surg. 2013;39(1):128-131. Moreno-Montañés J, Sabater AL, Barrio-Barrio J, Pérez-Valdivieso JR, Cacho-Asenjo E, García-Granero M. Risks factors and regression model for risk calculation of anesthesiologic intervention in topical and intracameral cataract surgery. J Cataract Refract Surg. 2012;38(12):2144-2153. Islam MN, Chakroborty S, Bandopadhay R, Mondal A. Sodium bicarbonate versus sodium hyaluronidase in ocular regional anaesthesia—a comparative study. J Indian Med Assoc. 2012;110(1):29-30, 39. Walsh F, O’Connor G. Regional anesthesia for cataract surgery. Ophthalmology. 2013;120(1):217-218. Jinapriya D, Almeida DR, Johnson D, Irrcher I, El-Defrawy SR. Anaesthetic plus dilating gel improves pupil dilation for cataract surgery. Can J Ophthalmol. 2012;47(2):145-149. Saygili O, Mete A, Mete A, Gungor K, Bekir N, Bayram M. Does phacoemulsification under topical anesthesia affect retrobulbar blood flow? J Clin Ultrasound. 2012;40(9):572-575. Khan B, Bajwa SJ, Vohra R, et al. Comparative evaluation of ropivacaine and lignocaine with ropivacaine, lignocaine and clonidine combination during peribulbar anaesthesia for phacoemulsification cataract surgery. Indian J Anaesth. 2012;56(1):21-26. Zhao LQ, Zhu H, Zhao PQ, Wu QR, Hu YQ. Topical anesthesia versus regional anesthesia for cataract surgery: a meta-analysis of randomized controlled trials. Ophthalmology. 2012;119(4):659-667. Hou CH, Lee JS, Chen KJ, Lin KK. The sources of pain during phacoemulsification using topical anesthesia. Eye (Lond). 2012;26(5):749-750. Blum RA, Lim LT, Weir CR. Diplopia following sub-Tenon’s anaesthesia: an unusual complication. Int Ophthalmol. 2012;32(2):191-193. Dogan R, Karalezli A, Sahin D, Gumus F. Comparison of sedative drugs under peribulbar or topical anesthesia during phacoemulsification. Ophthalmic Surg Lasers Imaging. 2012;43(2):121-127.

8 Preparation of the Patient and the Operating Field Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD After selecting the patient for cataract surgery, it is necessary to prepare him or her properly for the operation. A few arrangements in this preparation phase are crucially important to ensure optimal execution of the surgery. To begin with, the patient must remove items such as ties, tight clothes, or tight collars that could hinder breathing or make it difficult for the anesthetist to access the chest (to monitor vital signs such as cardiac activity and breathing) or the upper limbs (to control blood pressure or insert a needle for a drip or intravenous injection of emergency medication). The patient must be provided with appropriate shoe covers, surgical cap, and gown before entering the operating room. The operating room must have certain features, that is, it must be big enough for all the operating team to move comfortably (Figure 8-1) and the instruments must be near the surgical bed, without hampering the surgeon. It is crucially important that there are no cables or wires that limit movement of the pedals of the phacoemulsification machine and the microscope. To avoid this, some of these instruments have pedals with a Wi-Fi device. It is advisable that the operating room is soundproofed against noises that could distract the patient and the surgeon. Sterility must also be ensured by specific filtering systems and controlled air changes. The surgical light system must be positioned so that the scrub nurse’s table is correctly illuminated without hindering the illumination of the operating field. The monitors connected to the microscope must be positioned so that all the operating team can see them. Surgical materials must be classified and arranged in specific drawers and cupboards so that they are readily available if necessary.

Once the patient has entered the operating room, he or she is asked to sit/lie on the surgical bed or chair. In many cases, the patient is asked to lie on the surgical bed, which is then wheeled into the operating room. The patient’s head must be put in the correct position, making sure the neck is not hyper extended and checking the patient can breathe easily and his or her back and lower limbs are in a comfortable position. Finally, an inflatable device may be placed around the patient’s head, blocking it into position and avoiding sudden movements during surgery. Pillows can be used to obtain the right position of the head of patients affected by severe respiratory dysfunction or alterations of the spinal column such as kyphosis and scoliosis. In the case of patients with severe vascular insufficiency in the lower limbs, compression bandaging of the legs can be useful in order to avoid development of peripheral edema and venous and lymphatic stagnation, as well as avoiding thrombi caused by the patient’s legs being immobile during surgery (Figure 8-2). The execution of a good operation for cataract surgery begins with preparation of the operating field. It is very important to ensure good exposure of the globe in order to perform surgical maneuvers appropriately. After checking for good pupillary dilation, a few drops of anesthetic solution (4% lidocaine, single-dose drops) are instilled into each eye. In the contralateral eye, anesthesia reduces irritation and makes keeping it open during the operation easier. A transparent plastic shell with holes is then placed over it to stop the drape from irritating the eyelashes and stimulating the eyelids to close. The skin of the eyelids, the periocular region, the root of the nose, and cheekbone must be cleaned with gauze

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46  Chapter 8

Figure 8-2. Position of the surgeon with respect to the patient and the instruments.

Figure 8-1. The organization of the operating room includes precise order and position of the instruments, microscope, surgical bed, and the working space of the operating team.

dressing dipped in a solution with 5% to 10% concentration of povidone-iodine. The solution must be left on the skin for at least 3 minutes, after which the skin can be dried with a sterile gauze dressing so that the laminated drape adheres well. If patients cannot be treated with povidone-iodine (because of an allergy to it or they suffer from hyperthyroidism), a 0.05% chlorhexidine aqueous solution can be used instead. The conjunctival fornix is disinfected with a few drops of 5% povidone-iodine solution for about 3 minutes. The disinfectant is then washed away by irrigating with balanced salt solution (BSS). The next step is positioning the surgical drape, which is plastic and has a transparent, adhesive fenestration that is centered over the eye undergoing surgery. The patient is asked to keep his or her eyes open and look at the ceiling, so that the fenestration’s adhesive area adheres to the eyelashes. The plastic is cut with a small pair of scissors, making sure no damage is caused to the skin, conjunctiva, or (worse still) the cornea. The speculum is positioned next.

If the patient’s eyelashes have not been properly covered by the plastic drape, a Tegaderm (3M) dressing should be applied to keep the eyelashes out of the operating field before placing the speculum. Surgical drapes with a special opening to isolate the eye undergoing surgery are available. Once put in position, these drapes require a Tegaderm dressing to cover the eyelashes and keep them away from the operating field. The speculum is then put into place. It is important that the speculum does not weigh down onto the eye and does not lose grip during surgery. It must not alter the forces acting on the globe by compressing or stretching the walls of the eye—this is crucial to avoid negative effects on the execution of the incisions and especially during phacoemulsification and other surgical procedures. The speculum can be single or bivalve—both are equally satisfactory. The surgeon decides which one to use. If a single speculum is chosen (ie, a pair of singles with an elastic band), the elastic band is fixed onto the surgical drape with Klemmer forceps to obtain good exposure of the eye. The advantage of two single speculums is that patients find them less irritating and trauma is reduced, so there are fewer chances that the patient will involuntarily contract palpebral muscles, causing the expulsion of the instrument. They are more versatile and can be used to obtain a good palpebral aperture even in patients with particularly deepset eyes. They do not hinder the surgeon’s movements. Bivalve speculums can have open or closed valves and can be adjusted with a screw. Patients find them a little more irritating compared with single speculums and, in the case of poorly cooperative patients who contract palpebral muscles, they can cause superficial abrasions to the skin. Once the speculum is in place and good exposure of the eye is ensured, the eye and the fornices can be irrigated with BSS to remove any residual disinfectant. This wash is also useful to remove any secretions and to hydrate the corneal surface, which makes it easier for the surgeon to have a good view of the cataract and of all the structures of the

Preparation of the Patient and the Operating Field   47 anterior segment. If there are eyelashes that have not been covered by the drape or Tegaderm dressing, they must be removed by cutting them with the blunt-tip scissors, making sure the skin of the palpebral edge is not cut. Excess areas of the surgical drape’s transparent plastic must be removed to obtain good exposure of the eye. The disinfection procedure of the operating field described previously and the pre-, intra-, and postoperative antibiotic therapy are part of the guidelines published by the European Society of Cataract and Refractive Surgery for the prevention of postoperative endophthalmitis.1-3 If peribulbar anesthesia has been chosen, the patient preparation procedure is very similar, with the exception of the positioning of the transparent window of the surgical drape. In this case, using sterile gauze dressing or the rigid support of a sponge, the patient’s eyelids can be opened so that the eyelashes adhere properly to the drape.

REFERENCES 1.

2.

3.

Endophthalmitis Study Group, European Society of Cataract & Refractive Surgeons. Prophylaxis of postoperative endophthalmitis following cataract surgery: results of the ESCRS multicenter study and identification of risk factors. J Cataract Refract Surg. 2007;33(6):978-988. Barry P, Seal DV, Gettinby G, Lees F, Peterson M, Revie CW; ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: preliminary report of principal results from a European multicenter study. J Cataract Refract Surg. 2006;32(3):407-410. Erratum in: J Cataract Refract Surg. 2006;32(5):709. Seal DV, Barry P, Gettinby G, et al; ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: Case for a European multicenter study. J Cataract Refract Surg. 2006;32(3):396-406. Erratum in: J Cataract Refract Surg. 2006;32(5):709.

9 Incisions Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD The incision is the first step of cataract surgery and it can affect the execution of the surgical procedure, especially if it is not performed correctly.1 In phacoemulsification, incisions are required to allow entry to the probe of the ultrasound tip, to the irrigation/aspiration probes, and to accessory instruments (Figure 9-1). All the above must take place with minimal leakage of infusion fluids to ensure that the anterior chamber is sufficiently stable throughout the procedure. With the introduction of phacoemulsification, incision techniques have changed significantly compared to the incisions performed for intracapsular or extracapsular extractions. A small incision means the wound heals more quickly and postoperative astigmatism is reduced. Anterior chamber leakage during surgery is very limited, which reduces the risk of accidental damage to intraocular tissues caused by surgical instruments.2 Fewer sutures are required. The ideal corneal incision must therefore ensure sealing capacity during the operation, easy access for instruments, should not require suturing, and, most importantly, it must not cause astigmatism. To meet all these criteria, it must be small and have a specific geometry. The size, site of incision, and structural characteristics determine the postoperative behavior of corneal curvature and are therefore the crucial element in controlling the astigmatism induced by cataract surgery. The site of the main incision can be temporal or superior (depending on the surgeon’s habits). Both ensure good maneuverability of the intraocular instruments. When operating on astigmatic patients, it is preferable to position the main incision on the steepest astigmatism

axis in order to reduce corneal tension and partially correct the refractive error. The purpose of the incision is to open the anterior chamber. It can be made at different points, depending on the needs and features of the eye undergoing surgery. Corneal incision (or “clear corneal incision”): This incision means keeping away from the conjunctiva and iris root, which reduces the chances of iris prolapse or postoperative synechiae. The maneuvers for cataract removal are easier. The absence of vascularization in the cornea ensures there is no bleeding, although healing takes longer. Limbal: This is the most commonly used site because performing a tunnel incision (ie, on several planes) provides a larger and better surface in the corneal cut, which means that, at the end of surgery, there is good alignment of the flaps, the incision is self-sealing, and suturing is not required. Wound healing is excellent. The incision can be anterior (toward the cornea), median, or posterior. The closer the incision is to the cornea, the lower the risk of bleeding. However, healing times increase and a higher degree of astigmatism is induced. Working in a posterior position carries the risk of making the incision coincide with the iris root, which means it can prolapse into the wound and hinder correct execution of surgery. Scleral: This incision is made behind the corneal limbus, on multiple planes (scleral tunnel) because of the presence of ciliary bodies. The chances of inducing postoperative astigmatism are greatly reduced because the rigidity of the limbal ring is different from the cornea. There is no involvement of the iris root and angle structures and the integrity of Bowman’s membrane is preserved. The maneuvers for

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50  Chapter 9

Figure 9-1. Introduction into the anterior chamber of the tip of the phaco handpiece through the corneal incision. It is very important to check that the holes in the sleeve—through which the balanced salt solution flows—are in the anterior chamber.

phacoemulsification are slightly more complicated because of the lens distance, but the wound is easily self-healing and does not require suturing.

THE CONJUNCTIVA AND SURGICAL INCISIONS Pure corneal incisions do not require opening the conjunctival tissue, whereas limbal or scleral incisions require the conjunctiva to be cut. Cutting the conjunctiva implies the creation of a flap, which can be fornix based or limbus based. Often the conjunctiva is cut at limbus level, creating a fornix-based flap. With this technique, a small radial cut at the level of the limbus is made with a pair of Vannas microscissors, 2 to 4 mm in length. The closed scissors are then inserted into the cut, causing a dissection of the conjunctiva using the non sharp part of the blades and opening the scissors. Finally, a cut of the required length is made in the conjunctiva at limbal level, followed by another cut radially directed toward the fornix. To create a limbusbased flap, the conjunctiva needs to be cut with the Vannas scissors at about 4 to 5 mm from the limbus (keeping parallel to the limbus). Two radial cuts are then performed up to the limbus, thus creating a flap that can be folded over onto the cornea. The limbus-based conjunctival flap is normally used when a scleral or limbal incision is planned for cataract surgery or to implant an artificial lens into the anterior

Figure 9-2. Single-plane corneal incision. The orientation of the incision is very important: the more parallel it is to the corneal surface, the greater its sealing capacity because any force applied perpendicularly pushes the two flaps of the incision together.

chamber (phakic or aphakic). The fornix-based conjunctival flap is more frequently used in glaucoma filtration surgery because with this approach, it is possible to obtain a filtering bleb that extends posteriorly, a bleb that heals better, and a filtering bleb with a milder healing reaction, thus less likely to fibrose. Nylon, Vicryl (Ethicon, Johnson and Johnson), silk, or bipolar diathermy can be used to close the conjunctiva at the end of the operation.

Main Incision Incisions can have different features depending on the used plane(s). Single-plane incision: A full-thickness cut at the anterior limbal level is performed. It can be perpendicular or angled at various degrees (Figure 9-2). If it is perpendicular to the cornea, the contact area of the cut’s flaps is limited, whereas in angled cuts the contact surface of the flaps is larger. The orientation of the incision is very important: the more parallel it is to the cornea, the higher its sealing capacity because any force applied perpendicularly pushes the two flaps of the cut together. This can be very useful to the surgeon; for example, if sudden intraoperative ocular pressure occurs because the pressure acts perpendicularly to the cut’s orientation and causes the flaps to seal the wound. The ratio between length and width of the wound area ensures the wound is impermeable. When performing a vertical incision, the blade encounters symmetrical lateral resistance in the tissue, so it is quite easy to predict what

Incisions  51

Figure 9-3. Profile of a two-plane corneal incision.

Figure 9-4. Three-plane incision at the scleral level.

the incision will be like. In the case of an angled incision, tissue resistance can be asymmetrical because it is related to the presence of interlamellar spaces, which offer less resistance and can cause the direction of the incision to be less predictable. A vertical incision is not difficult to perform but care must be taken to ensure the depth is the same at every point of the cut. To achieve this, scalpels with precalibrated blades can be used (such as scalpels with a diamond blade). To begin with, horizontal dissection implies making a vertical incision with a defined thickness. Next, with the use of specific, flat blades with sharp edges (crescent knife), the real dissection and penetration into the chamber can be performed. Two-plane incision: This incision is performed at limbal level or on the cornea or sclera, keeping close to the limbus. The incision is on two planes, one perpendicular to the corneal surface and one at a 110-degree angle (approximately). The two cuts are performed in sequence, beginning with the perpendicular cut (penetrating through about half the thickness of the cornea) and then making the cut on the angled plane, until the anterior chamber is entered (Figure 9-3). The incision obtained this way can seal off the anterior chamber very well during the operation. With this cut, the phases of aspiration of nuclear masses and of the viscoelastic substance and the insertion of the artificial lens are easier. Sutures may not be necessary or, if they are, they do not need to be taught (Figure 9-4). Three-plane or self-sealing corneal tunnel3: The first plane of the incision is a clear corneal incision, in front of the limbal vessels, about 250-mm deep. The width depends on the kind of lens to be implanted and is usually 2.75 mm. The

first cut is perpendicular to the corneal plane (Figure 9-5). The second plane (which creates a cleavage in the corneal stroma) can be executed in various ways (Figure 9-6). Entry into the anterior chamber is performed directly using an angled diamond scalpel and following a plane parallel to the iris or indenting the blade and directing it toward the anterior apex of the lens (Figure 9-7). Alternatively, the stromal cleavage is created with a blunt blade, followed by the creation of the stromal tunnel using a calibrated blade to enter the anterior chamber. The third option is to use a 2.75-mm calibrated blade to create the stromal tunnel of the desired length and, tilting the blade toward the lens, access into the anterior chamber is obtained (Figure 9-8). For all kinds of incisions, the sealing properties depend almost exclusively on the internal corneal valve and, to a lesser extent, on the total width of the incision. The control of astigmatism depends on the length of the tunnel— normally, the tunnel is neutral if it has a square shape (ie, the width and the length are the same). Obviously an excessively long tunnel makes surgical maneuvers more difficult, whereas if the tunnel is short and the incision wide, suturing should be planned to avoid causing astigmatism. The healing of the internal corneal valve means the suture, if applied, can be removed early, with limited changes in astigmatism. Three-plane or scleral tunnel: A perpendicular cut in the sclera is performed first (Figure 9-9), followed by dissection in an interlamellar space, proceeding horizontally, up to the cornea (Figures 9-10 and 9-11), and finally entering into the anterior chamber with an oblique cut (Figure 9-12). The advantages of this kind of approach are having a “tight,” selfhealing wound that does not require suturing and the preservation of the limbal ring (a crucially important element

52  Chapter 9

Figure 9-5. Corneal preincision performed with a 30-degree blade.

Figure 9-6. Second phase of the incision performed with a crescent knife to keep a direction parallel to the cornea.

Figure 9-7. Second phase of the three-plane incision performed with a diamond scalpel.

Figure 9-8. Profile of the three-plane incision.

in reducing the induction of postoperative astigmatism). The sealing capacity of a tunnel incision is significantly influenced by the length of the incision—incisions as long as or longer than 4 to 5 mm always require at least one safety suture.

STEP-BY-STEP EXECUTION OF A GOOD SCLERAL TUNNEL 1. After the conjunctival incision, a diathermy probe is used for a mild cauterization of the area, which avoids bleeding during the preparation of the scleral area chosen for access. Cauterization must be gentle because it causes thinning of the tissue and retraction of collagen

Incisions  53

Figure 9-9. Step 1: Perpendicular incision of the sclerocorneal tunnel.

Figure 9-10. Step 2: Dissection inside an interlamellar space, horizontally.

Figure 9-12. Step 3: Penetration into the anterior chamber, oblique orientation.

Figure 9-11. Step 2: Side view of the direction taken by the keratome.

fibers. It also causes postoperative with-the-rule astigmatism (which can be more or less reversible in time). 2. Next, a vertical cut in the sclera is performed. The incision’s distance from the limbus varies and depends on the width of the incision; for example, a 4-mm incision is made at a 2-mm distance (approximately) from the limbus, whereas a 5-mm incision is at about 3-mm distance. The incision cuts into about half the scleral thickness and it can be straight, concave, convex, triangular, or radial. The site of incision is important to obtaining a reduced astigmatism effect and must be in Koch’s incisional funnel (an imaginary area projected

onto the sclera and with the shape of an upside-down funnel, tighter near the limbus and gradually wider approaching the fornix). The fundamental rule to avoid unexpected postoperative astigmatism is to consider that induced astigmatism decreases as the distance from the limbus increases. In a concave incision that is parallel to the limbus, the flaps tend to move apart along the entire length of the incision, which causes against-the-rule astigmatism. A linear incision moves the ends of the cut apart and therefore induces a lower degree of deformation. Finally, a convex incision (frown incision) brings the anterior extremity closer to the limbus and moves the ends away, which has a double advantage; that is, there is better control when performing maneuvers with instruments in the

54  Chapter 9

B

A

Figure 9-13. Placement of the two side-port incisions in the cornea with a 19-gauge blade.

anterior chamber and the effect on corneal deformation is limited. 3. Lamellar dissection is started using a scalpel with a rounded blade and sharp edges. The instrument is inserted into the incision at a 45-degree angle (approximately) and the superficial flap is gently grasped with a Pierce-Hoskin forceps, while the blade’s orientation is made parallel to the scleral surface exerting a slight downward pressure. In this way, it is possible to identify a cleavage plane along which the blade can penetrate. The dissection continues under very careful monitoring until the rounded tip of the blade appears clearly at the level of the transparent cornea. It is crucially important to cross Schwalbe’s line in order to obtain a watertight tunnel and to keep away from the angle region (to avoid problems during the surgical maneuvers). A pointed blade is used to enter into the anterior chamber. The instrument is kept at 30- to 45-degree angle with Descemet’s membrane by lifting the handle and causing a slight indentation. The tip is positioned at the level of the closed end of the tunnel and pushed into the anterior chamber. The tunnel obtained in this way is comfortable to work through during the various steps of phacoemulsification and insertion of the artificial lens. At the end of the procedure, the conjunctiva is closed by applying one or more sutures or via coagulation with a diathermy probe.4

SIDE-PORT INCISION The lateral side-port incision is the access route for the injection of the viscoelastic substance. It is especially important for the insertion of the olive-tip spatula, the chopper, or lens hook, which are used to stabilize the eye, control the movements of the lens, perform nucleus fragmentation, move the iris away during cortical aspiration, make the insertion of the intraocular lens easier, and correct its position. The side-port incision is made in front of the limbal arcades, on the left (for a right-handed surgeon). It must

be about 1 mm in width and oriented so that the internal corneal surface is beveled, which makes it is easier to keep it watertight at the end of surgery. Essentially, a first path is created with the tip of the blade perpendicular to the corneal surface, then the tip is oriented tangentially to the iris until penetrating into the anterior chamber enough to obtain the desired width (Figure 9-13). In the bimanual technique, two accessory incisions are made (for the irrigation and aspiration probes).

MICROINCISION TECHNIQUE IN CATARACT SURGERY The microincision cataract surgery (MICS) expression—commonly used today—was coined by Dr. Jorge Aliò and still is the acronym that best sums up the main advantages of this surgical technique, beginning with the possibility of performing surgery to reduce the development of iatrogenic postoperative astigmatism, which could cause patients to need glasses with corrective lenses.5 A number of studies have shown that postoperative corneal astigmatism is related to the size of the incision, especially if above 3 mm.6,7 Deterioration of the cornea’s optical quality has been shown to occur after larger incisions have been performed. The deterioration is caused by an increase in higher-order aberrations, particularly third-order aberrations such as trefoil.8 The reduction in the size of corneal incisions—2 mm or smaller cuts—represented the birth of MICS with bimanual or coaxial technique. In the coaxial technique (C-MICS), the size of the corneal incision is in the 1.8- to 2-mm range to allow entry of the phacoemulsification tip and infusion sleeve that are integrated in the same handpiece. In the bimanual technique (B-MICS), the phacoemulsification tip is used without a microsleeve with an irrigating chopper. The phacoemulsification tip is separated from irrigation, which means the diameter of the incision can be further reduced to 1.4 mm per incision. Currently, B-MICS is the cataract surgery technique that requires the smallest incisions—even smaller incisions are

Incisions  55 likely to be required when technological innovation supplies smaller instruments and adequate intraocular lenses.9 Bimanual phacoemulsification can currently be used without restrictions in all patients and for the treatment of any kind of cataract. It is suitable as a routine procedure for the extraction of simple cataracts (with nuclei of varying degrees of hardness and density) or complex cataracts. The B-MICS technique can easily be used to operate on subluxated, post-traumatic, and congenital cataracts, and cataracts during vitrectomy,10,11 using low amounts of ultrasound. B-MICS users say the technique makes the anterior chamber more stable due to the reduction of leakage through the microincisions12 and better followability due to the separation of infusion from aspiration.13,14 The use of an irrigating chopper as a second surgical instrument improves management of the irrigation flow that can be oriented in a more rational and useful manner. The possibility of switching the probes from one hand to the other allows the surgeon 360-degree movement in the anterior segment,15 directing infusion and aspiration as needed. The reduction in phacoemulsification times makes surgery more efficient and reduces iatrogenic damage. The execution of the various phacofragmentation phases in a closed ocular system with stable chamber provides excellent visibility, which is further improved by the miniaturization of surgical instruments.16 The B-MICS technique offers many advantages related to patient outcome because the microincisions induce negligible astigmatism and very low aberrometry alterations17,18 associated with faster postoperative recovery and excellent final visual acuity19–21— these aspects in particular are extremely important at present, when cataract surgery is increasingly becoming more refractive and aimed at providing patients with quality vision for better quality of life. Last but not least is the fact that microincisions reduce the risk of intraoperative infection and complications. The mini-incision coaxial phacoemulsification technique requires an incision in the 1.8- to 2.2-mm range to allow the passage of the phaco tip with a sleeve. When performing MICS, the main incision is used to introduce the capsulorrhexis forceps, the tip of the phacoemulsification device, and the irrigation/aspiration probe (which in this case can be coaxial or bimanual). It is also used to inject the viscoelastic substance during the capsular bag filling phase (before insertion of the artificial lens) for the entry of the lens injector and for the aspiration of the viscoelastic substance with the irrigation/aspiration handpiece. The execution of this coaxial technique requires a secondary or accessory incision for introduction of the instruments that help in the phacoemulsification maneuvers and that are used to control the movements of the globe. The coaxial microincision technique has the advantage of making surgical instrument movements easier, thanks to a larger main incision, without the increased size negatively affecting induced postoperative astigmatism. In the

case of capsulorrhexis in particular, the forceps can be moved more easily, making this surgical step more fluid and continuous. The control of spaces via the injection of viscoelastic substances is good even if it is essential that the incisions are performed correctly and are watertight (this is especially important for the coaxial technique, but slightly less important for the bimanual technique). Using the coaxial microincision technique, in which there is a sleeve on the tip of the handpiece and on the irrigation/aspiration handpiece, the chamber can be kept in a more stable condition during the steps of cataract nucleus capture and fragmentation, and during aspiration of the cortex. The higher fluctuation of the anterior chamber seen when using the bimanual technique is apparently caused by the unstable balance between the aspiration of the phaco tip and the irrigation of the irrigating chopper. Furthermore, during these maneuvers, the incisions seem to be more open because of the lack of “plug” effect provided by the sleeve. The disadvantage of the coaxial irrigation/aspiration handpiece (compared to the separate probes used in the bimanual technique) is that it makes the aspiration of cortex less easy, especially near and beneath the main incision because aspiration requires directing the tip vertically, which carries the risk of stressing the incision, reducing its sealing capacity, and, therefore, causing fluctuation of the anterior chamber. Additionally, the presence of irrigation near the aspiration tip often pushes cortex away during aspiration. There is no doubt that having two separate probes during irrigation/aspiration of cortex makes it easier to control aspiration, pushing away the margins of the anterior capsulorrhexis, the posterior capsule, or the pupillary margin if it is flaccid. An additional advantage of the sleeve is the cooling of the phaco tip, which reduces the risk of burns in the corneal tunnel. The water flowing in the sleeve prevents the phaco tip from overheating.

REFERENCES 1.

2.

3.

4. 5.

6.

Bolz M, Sacu S, Drexler W, Findl O. Local corneal thickness changes after small-incision cataract surgery. J Cataract Refract Surg. 2006;32(10):1667-1671. Tint NL, Dhillon AS, Alexander P. Management of intraoperative iris prolapse: stepwise practical approach. J Cataract Refract Surg. 2012;38(10):1845-1852. Yaguchi S, Yaguchi S, Asano Y, et al. Repositioning and scleral fixation of subluxated lenses using a T-shaped capsule stabilization hook. J Cataract Refract Surg. 2011;37(8):1386-1393. Gomaa A, Liu C. Bowl-and-snail technique for soft cataract. J Cataract Refract Surg. 2011;37(1):8-10. Kim EC, Byun YS, Kim MS. Microincision versus small-incision coaxial cataract surgery using different power modes for hard nuclear cataract. J Cataract Refract Surg. 2011;37(10):1799-1805. Hayashi K, Hayashi H, Nakao F. The correlation between incision size and corneal shape changes in sutureless cataract surgery. Ophthalmology. 1995;102:550-556.

56  Chapter 9 7.

8.

9.

10.

11.

12.

13.

14.

Olson RJ, Crandall AS. Prospective randomized comparison of phacoemulsification cataract surgery with a 3,2 mm vs a 5,5 mm sutureless incision. Am J Ophthalmol Vis Sci. 1998;125:612-620. Guirao A, Tejedor J, Artal P. Corneal aberrations before and after small-incision cataract surgery. Invest Ophthalmol Vis Sci. 2004;45:4312-4319. Nagappa S, Das S, Kurian M, Braganza A, Shetty R, Shetty B. Modified technique for epinucleus removal in posterior polar cataract. Ophthalmic Surg Lasers Imaging. 2011;42(1):78-80. Olson RJ. Clinical experience with 21 Gauge manual microphacoemulsification using Sovereign Whitestar Technology in eyes with dense cataract. J Cataract Refract Surg. 2004;30:168-172. Haripriya A, Aravind S, Vada K, Natchiar G. Bimanual microphaco for posterior polar cataract. J Cataract Refract Surg. 2006;914-917. Assaf A, El-Moatassem Kotb AM. Feasibility of bimanual microincision phacoemulsification in hard cataracts. Eye. 2007;21(6):807-811. Paul T, Braga-Mele R. Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol. 2005;16:2-7. Yao K, Tang X, Ye P. Corneal astigmatism, high order aberrations and optical quality after cataract surgery microincision versus small incision. J Refract Surg. 2006;22:1079-1082.

15. Soscia W, Howard JG, Olson RJ. Bimanual phacoemulsification through two stab incisions. J Cataract Refract Surg. 2002;28:1039-1043. 16. Cavallini GM, Masini C, Chiesi C, Campi L, Rivasi F, Ferrari P. Cataract development in a young patient lathosterolosis: a clinicopathologic case report. Eur J Ophthalmol. 2009;19(1):139-142. 17. Elkady B, Aliò JL, Ortiz D, Montalban R. Corneal aberrations after microincision cataract surgery. J Cataract Refract Surg. 2008;34:40-45. 18. Kaufmann C, Krishan A, Landers J, Esterman A, Thiel M, Goggin M. Astigmatic neutrality in biaxial microincision cataract surgery. J Cataract Refract Surg. 2009;35:1555-1562. 19. Hayashi K, Yoshida M, Hayashi H. Postoperative corneal shape changes: microincision versus small-incision coaxial cataract surgery. Cataract Refract Surg. 2009;35:233-239. 20. Tong N, He JC, Lu F, Wang Q, Qu J, Zhao YE. Changes in corneal wavefront aberrations in microincision and small-incision cataract surgery. J Cataract Refract Surg. 2008;34:2085-2090. 21. Denoyer A, Denoyer L, Marotte D, Georget M, Pisella PJ. Intraindividual comparative study of corneal and ocular wavefront aberrations after biaxial cataract surgery microincision versus coaxial small-incision. Br J Ophthalmol. 2008;92:1679-1684.

10 Viscoelastic Substances Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Viscoelastic substances are used during the various steps of cataract phacoemulsification surgery. Every step has its own specific problems and particular conditions, so the viscoelastic substance must be suitable for every step. The surgical steps in which a viscoelastic substance must be used are as follows: 1. Filling the anterior chamber (Figure 10-1): The viscoelastic substance must be easy to inject and ensure the space is well filled, which means it must be highly pseudoplastic with low viscosity during injection and have high viscosity when the anterior chamber is filled; that is, it must fill the eye spaces offering little resistance during injection and it must stay in the anterior chamber and keep it stable (Figures 10-2 and 10-3).1 2. Capsulorrhexis: The viscoelastic substance must preserve the anterior chamber’s depth, ensuring good visibility and good stability of the capsule and preventing fluctuations. It must be possible to keep the flap pressed downward, so that working with the surgical instruments on the capsule is not hindered. It is therefore essential that the viscoelastic substance is transparent, with high viscosity and elasticity. 3. Hydrodissection: During this phase, the viscoelastic substance must ensure the anterior chamber is stable when the cannula is introduced and positioned. It must also gradually leak out of the eye if too much balanced salt solution (BSS) is injected (to prevent an increase in intraocular pressure). To meet all these requirements, it must have a good degree of pseudoplasticity. 4. Phacoemulsification: During the entry of the ultrasound tip and phacoemulsification maneuvers, the viscoelastic substance must preserve eye spaces and

- 57 -

protect the delicate structures of the eye, so it must adhere to the endothelium, the iris, and the angle.2 It must be effective when the phaco tip, spatula, and irrigation handpiece are moved by the surgeon. It must make entry of BSS easy and allow the BSS to cool the phaco tip during the phacoemulsification of the nucleus.3 The properties of the viscoelastic substance must therefore make it poorly pseudoplastic (Figure 10-4). The phacoemulsification process is characterized by strong, turbulent flows of irrigation and aspiration fluid. The continuous flow tends to remove the viscoelastic material. A viscoelastic substance that remains in the eye (partly at least) is therefore necessary (chiefly to protect the corneal endothelium). On the one hand, the viscoelastic substance used must remain in the anterior chamber to protect the corneal endothelium and to ensure room for phaco maneuvers. On the other hand, its resistance to the turbulent flows of the irrigation liquid must be limited and it must exit the anterior chamber to avoid increased pressure when pressure rises. 5. Irrigation and aspiration: During this step, the viscoelastic substance must slowly leave the anterior chamber when the irrigation and aspiration probes are inserted, ensuring the anterior chamber is sealed. It must remain in the anterior chamber despite the high flow of BSS, and it is especially important that it does not mix with fluid and the cortex (hindering or blocking its removal). The characteristics of the viscoelastic substance used in this step are good adhesive properties and low cohesive properties. 6. Filling the capsular bag (Figure 10-5): During this step, the viscoelastic substance must be easy to inject and Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 57-63). © 2014 SLACK Incorporated.

58  Chapter 10

Figure 10-1. Injection of viscoelastic substance to inflate and stabilize the anterior chamber before performing capsulorrhexis.

Figure 10-3. Compartmentalization of the two viscoelastic substances: the dispersive substance will coat the corneal endothelium and the cohesive substance will create the spaces to insert the instruments.

Figure 10-2. Two different kinds of viscoelastic materials are injected in patients with severe dystrophy of the corneal endothelium—a cohesive one and a dispersive one—to protect the corneal endothelium.

Figure 10-4. A layer of dispersive viscoelastic substance remains on the endothelium during phacoemulsification, even if some of it is pushed out of the anterior chamber by irrigation.

Figure 10-5. Compartmentalization of the two viscoelastic substances: the dispersive substance will coat the corneal endothelium; the cohesive substance creates the spaces to insert the instruments.

Figure 10-6. Injection of viscoelastic substance to distend the capsular bag before insertion of the artificial lens.

remain stable in the capsular bag and the anterior chamber, so it must have high molecular weight and high pseudoplasticity. Finally, it must be easy to inject and distribute evenly so that the edges of the capsulorrhexis and the capsular bag can be clearly distinguished during the implantation of the intraocular lens (IOL)4 (Figure 10-6).

7. Maintenance of good capsular opening during the insertion, unfolding, and positioning of the IOL (Figure 10-7): In this step, the viscoelastic substance must have high molecular weight and high viscosity in order to maintain good capsular opening and, during injection of the IOL, its resistance to lens entry must be limited. The viscoelastic substances must exit the eye

Viscoelastic Substances  59

MAIN VISCOELASTIC SUBSTANCES

Figure 10-7. Enlargement of the capsular bag and the anterior chamber caused by the viscoelastic substance helps during the insertion of the artificial lens.

easily if an excessive amount is injected, so it must have high pseudoplasticity properties. During IOL unfolding, the viscoelastic substance must prevent the IOL from unfolding violently (this is particularly important for silicone IOLs), but it must allow the IOL to unfold gradually and easily. It must allow the surgeon to position and center the IOL in the capsular sac easily, so its pseudoplasticity must be low. Finally, it must be easy to remove completely during the irrigation and aspiration steps without causing the lens to move violently, so it must have low viscosity and good cohesive properties.5 Currently, the available viscoelastic substances have special features that allow surgeons to carry out every step of phacoemulsification safely and easily. Crucial factors in the selection of the most suitable viscoelastic substance are the skill and experience of the surgeon and the characteristics of the eye undergoing surgery. Briefly stated, the ideal viscoelastic substance for the correct execution of phacoemulsification must do the following: Be easy to inject ●

●

Maintain spaces

●

Protect the endothelium

●

Coat tissues

●

Be resistant to position changes

●

Permit effective tissue manipulation

●

Be easy to remove at the end of the operation

●

●

Must not undergo chemical or physical changes while in use Be transparent

To be suitable for use in the human eye, a viscoelastic substance must have some essential features; that is, it must be sterile, nontoxic, and apyrogenic; must not cause tissues to react and inflame; must not cause allergic reactions; must be chemically inert and electrolytically balanced; and must have the same osmolarity and colloid osmotic pressure of the cornea and aqueous humor. Finally, it must be pH buffered, water soluble, highly purified, devoid of particles, and transparent. Ultimately, it should be easy to inject into the eye and to aspirate and remove from the eye. It is also very important to consider the molecular weight, concentration, chemical composition, and, in addition, origin (natural or synthetic). Various kinds of viscoelastic substances are used in cataract surgery (Figure 10-8).

Sodium Hyaluronate This polysaccharide is made of sodium glucuronate and N-acetyl glucosamine. It does not contain amino acids or other carbohydrates, but every subunit has a single negative charge, which together are sufficient to neutralize the positive charges normally found on ocular tissues, instruments, and the surface of the IOL. Its molecular weight ranges between 500,000 and 6 million Dalton and it is made up of about 10,000 disaccharide units. The average diameter of a molecule is 10 nm. In liquids and in the aqueous humor in particular, hyaluronic acid occupies a large hydrodynamic volume because of its spiral structure that is compact but not pre-ordered, which gives it a typical “sponge” structure. The architecture of the chain layout (double helical structure) is the basis of the viscoelastic and pseudoplastic properties of this molecule. At high concentrations, the chains it is composed of are organized in a complex tridimensional arrangement. The viscosity of the substance is directly related to the concentration of sodium hyaluronate (a fivefold increase in concentration produces a 1000-fold increase in viscosity) and to the molecular weight (length of the molecular chain). In the case of Healon, the first viscoelastic substance used in cataract surgery, the elastic properties were found to prevail on viscosity, starting at low values of concentration and flow—it can be easily injected through a 30-gauge cannula and, after exiting the needle cannula, it returns to its original high viscosity and shape. The origin of the substance does not change the chemical structure, but it does affect the molecular weight. The residual hyaluronic acid in the anterior chamber is removed at the end of surgery following the path of the aqueous humor, exiting normally through the trabecular meshwork (Table 10-1).

60  Chapter 10

A

B

C

Figure 10-8. (A) DisCoVisc (Alcon). (Reprinted with permission from Alcon Laboratories.) (B) Family of AMO viscoelastic substances used in cataract surgery. (Reprinted with permission from Abbott Medical Optics.) (C) Family of Bausch & Lomb viscoelastic substances used in cataract surgery. (Reprinted with permission from Bausch & Lomb.)

Hydroxypropyl Methylcellulose Hydroxypropyl methylcellulose is currently used more as a visco-adhesive substance than a viscoelastic one because its capacity to have elastic properties is limited. For this reason, it needs to be injected through a large diameter cannula with higher pressure compared to viscous substances containing hyaluronic acid. The large chains have a more limited capacity to rotate around their central axis, which means the molecule is quite rigid. In a solution, it is less elastic and has more limited shock-absorbing capacity. Because it has lower molecular weight and is not very viscous, it does not have enough pseudoplasticity, which means the following: Limited capacity to maintain the anterior chamber in conditions of high vitreous pressure—difficult to remove ●

●

Good coating of the surface of tissues, instruments, and intraocular implants (because of its visco-adhesive properties)

●

Limited transparency

●

Storage at room temperature, readily available

●

Can be sterilized in an autoclave

It is currently mainly used for extraocular purposes (ie, on the cornea to protect the epithelium and improve intraoperative visibility for the surgeon). Examples: OcuCoat, manufactured by Bausch & Lomb (B&L); hydroxypropyl methylcellulose 2% is used directly on the cornea and provides a good view of intraocular structures. Its low molecular weight makes it easy to remove from the cornea’s surface. If injected into the anterior chamber, OcuCoat preserves spaces very well during surgical maneuvers and is easy to remove.

Chondroitin Sulfate Chondroitin sulfate’s chemical and physical properties are similar to those of hyaluronic acid. Both are made of disaccharide units. The sulfate group gives the molecule a double negative charge, so it is more efficient at neutralizing the positive charges normally found on ocular tissues and instruments. This chemical property confers a higher coating capacity. Viscoat (Alcon) is a viscoelastic substance containing a mixture of 4% chondroitin sulfate and 3% hyaluronic acid in a 1:3 ratio. Combined, these two polymers make a high-molecular-weight compound with medium-high viscosity, which maintains spaces well and provides adequate

Rooster crest

Rooster crest

Bacterial fermentation (hyaluronic acid)

Bacterial fermentation (hyaluronic acid)

Bacterial fermentation 40,000 ± 20,000 cps (hyaluronic acid); shark 325 mOsm/kg fin (chondroitin sulfate)

Bacterial fermentation 40,000 to 110,000 (hyaluronic acid); shark mPas/ fin (chondroitin sulfate) 260-370 mOsm/kg

Rooster crest

Rooster crest

Rooster crest

Rooster crest

Healon GV 1.4%

Healon 5 2.3%

Provisc

Biolon

Viscoat

DisCoVisc

Amvisc

Amvisc plus

ViTrax

MicroVISC

VISTHESIA 1.0%-1.5%

300,000 mPas/ 302 mOsm/kg

Rooster crest

Healon 1%

336 mOsm/kg

310 mOsm/kg

318 mOsm/kg

30,000 mPas/ 340 mOsm/kg

25,000 mPas/ 310 mOsm/kg

7,000,000 mPas

3,000,000 mPas/ 310 mOsm/kg

Viscosity/ Osmolarity

Commercial Source Name

7.0 to 7.5

7.0 to 7.5

6.5 to 7.2

6.5 to 7.2

7.0 to 7.5

7.3

7.2

7.0 to 7.5

pH

Cohesive and dispersive

Cohesive

Cohesive

Cohesive

4 million Da

645,000 Da

1 million Da

1 million Da

Cohesive

Adhesive

Cohesive and dispersive

Cohesive

Viscousdispersive

Chondroitin sul- Adhesive fate: 22,500 Da, sodium hyaluronate: 500,00 Da

3 million Da

Zeiss

Bohus Biotech

AMO

B&L

B&L

Alcon

Alcon

SIFI

Alcon

AMO

AMO

AMO

1.0% hyaluronic acid + 1.0% lidocaine 1.5% hyaluronic acid + 1.0% lidocaine

1.0% hyaluronic acid

3.0% hyaluronic acid

1% long chain hyaluronic acid

Hyaluronic acid

1.0 mL 40 mg chondroitin sodium sulfate and 17 mg sodium hyaluronate

4% chondroitin sulfate + 3% hyaluronic acid

1.0 mL 1.0% hyaluronic acid

0.4 mL 1.1% hyaluronic acid

0.60 mL 2.3% sodium hyaluronate

0.55 mL 1.4% sodium hyaluronate 0.85 mL 1.4% sodium hyaluronate

0.40 mL 1.0% sodium hyaluronate 0.55 mL 1.0% sodium hyaluronate 0.85 mL 1.0% sodium hyaluronate

Classification Company Concentration and Content of the Syringe

1.9 to 2.5 million Cohesive Da

4 million Da

5 million Da

4 million Da

Molecular Weight

PRODUCTS CONTAINING HYALURONIC ACID, WITH MOLECULAR WEIGHT AND OTHER FEATURES IMPORTANT IN CATARACT SURGERY

TABLE 10-1.

Viscoelastic Substances  61

62  Chapter 10 visco-manipulation of tissues. It is also very easy to inject, adheres well to the corneal endothelium (because of the negative charges on the molecular surface), and provides good protection from vibrations during phacoemulsification. Negative aspects include the reduction of transparency (because of the irregular interface between the surfaces of Viscoat and the aqueous humor) and its difficulty to remove during irrigation/aspiration because it adheres very well to surfaces (a plus during some surgical steps), due to the molecule’s lower cohesive properties.

PHYSICAL AND RHEOLOGICAL PROPERTIES OF VISCOELASTIC SUBSTANCES The laws that govern the behavior of a viscoelastic substance when immobile and moving are the basis for the definition of the type of viscoelastic substance. Viscosity must be considered the resistance met by the particles of a body when they slide against each other (also called internal friction). Its manifestation is the development—as one layer flows with respect to the other—of superficial tensions that can be higher or lower depending on the nature of the body. The viscosity of a substance depends on its molecular weight, its concentration, temperature, and solvent used in the aqueous solution. A viscoelastic substance with high molecular weight (determined by a large molecular chain) has high viscosity at 0 value (highest speed) of the flow speed gradient of the substance (shear rate)—in other words, when inert, not moving (eg, Healon GV). Using this property, the surgeon can preserve large, stable spaces in a way that is proportional to the weight and viscosity of the examined substance. The highest viscosity of a product at 0 shear rate determines its stabilizing effect. The medium viscosity at intermediate shear rate produces the mobilizing effect and the minimum viscosity at high shear rate determines how easy the product is to inject (eg, Provisc). Pseudoplasticity is the capacity of a substance to switch from a state of high viscosity and rigidity (before injection) to a fluid, low-viscosity state, during which internal friction decreases and the substance can flow and be injected. It is a fundamental property of polysaccharide molecules (Healon GV, Healon, Provisc) because it determines these molecules’ capacity to maintain spaces and to be injected. As the shear rate increases, the polysaccharide chains align following the direction of the flow, so viscosity decreases. This property does not just emerge when the substance flows through an injection cannula—it appears when surgical instruments move in the viscoelastic substance, so steps such as irrigation and phacoemulsification easily cause the

extrusion of the polysaccharide viscoelastic substance from the anterior chamber. Pseudoplasticity is a crucial characteristic of viscoelastic substances—the different levels of viscosity a substance achieves by changing its rheological state (from viscous to fluid) allow the surgeon to perform many intraocular maneuvers. The ideal viscoelastic substance must also have good viscosity, which keeps intraoperative spaces stable, but it must have equally good pseudoplasticity so that it can be easily removed from the anterior chamber when it is no longer necessary. Elasticity is the tendency of a given viscoelastic substance to return to its original shape after compression or deformation. Long-chain molecules (such as Healon, Healon GV, Provisc, and Biolon) are more elastic compared to substances with short molecular chain (such as Viscoat). The mechanical energy applied at low frequency causes the macromolecules to rearrange and “slide” over each other, creating a viscous type of movement. This is the kind of movement observed during the release of soft, foldable IOLs. If a fast, high-frequency impact is applied, the chains become deformed and the mechanical energy is transformed into elasticity. The chains will then return to their original shape. An increase in the viscosity of the viscoelastic substance produces an increase in its elastic properties, with a tendency to restore the original volume after a deformation event. Viscoelasticity is a crucially important property because it protects against the energy released by vibrations during phacoemulsification (highfrequency energy) and by the turbulence caused during irrigation/aspiration. Cohesivity defines the degree to which a substance adheres to itself and is a function of molecular weight and elasticity. It is proportional to viscosity at 0 shear rate values. Viscoelastic substances made of a long molecule with high molecular weight tend to have high internal cohesivity, so they are easy to suck and exit the eye as a single mass. Substances with this feature are made of high or very high molecular weight hyaluronic acid (such as Healon GV, Healon, Biolon, Provisc), whereas substances with short molecular chain and low molecular weight are less cohesive because they tend to fragment. They are by nature more difficult to draw out (Viscoat). Internal cohesivity is an advantage when maintaining intraoperative spaces, but it can cause jamming in the trabecular meshwork (leading to ocular hypertension) if it is not completely removed. Surface adhesivity is the capacity of viscoelastic substances to bind and adhere (to varying degrees) to the surface of tissues, instruments, and IOLs. Surface adhesivity or wettability can be measured by assessing superficial tension and the contact angle. Low superficial tension associated with a small contact angle means the substance adheres very well to a given surface. Substances that have a higher negative charge on their surface (Viscoat) are better at neutralizing the positive charges found on instruments

Viscoelastic Substances  63

Substance

Molecular Weight

Viscosity

Cohesivity

Adhesivity

Healon

4.0 M

200,000

High

Low

Healon GV

5.0 M

2,000,000

High

Low

Viscoat

500 K (hyaluronic acid) 25 K (CDS)

41,000

Low

High

OcuCoat

86 K

5400

None

High

Provisc

1.9 to 2.5 M

150,000

High

Low

Biolon

3M

150,000

High

Low

Amvisc

1.0 M

100,000

High

Low

Amvisc plus

1.5 M

84,000

Medium

Medium

Medium

Medium

Medium

High

DisCoVisc IAL F

1.0 M

61,500

and tissues, which increases their ability to adhere to the corneal endothelium and to provide better protection.

REFERENCES 1.

Floyd M, Valentine J, Coombs J, Olson RJ. Effect of incisional friction and ophthalmic viscosurgical devices on the heat generation of ultrasound during cataract surgery. J Cataract Refract Surg. 2006;32(7):1222-1226.

2. 3. 4.

5.

Malavazzi GR, Nery RG. Visco-fracture technique for soft lens cataract removal. J Cataract Refract Surg. 2011;37(1):11-12. Carifi G. Visco-fracture technique for phacoemulsification. J Cataract Refract Surg. 2011;37(5):978. Berger A, Contin IN, Nicoletti G, Baltar Pazos PF, Baltar Pazos HS, Gomes JÁ. Middle prechop: fracturing the middle portion of the nucleus. J Cataract Refract Surg. 2012;38(4):564-567. Varma D, Baylis O, Wride N, Phelan PS, Fraser SG. Viscogonioplasty: an effective procedure for lowering intraocular pressure in primary angle closure glaucoma. Eye (Lond). 2007;21(4):472-475.

11 Capsulorrhexis Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Continuous circular capsulorrhexis (CCC) was devised in the mid-1980s by Gimbel and Neuhann. Compared to the capsulotomy, which was previously performed during cataract surgery, CCC has many advantages, starting with the fact that the continuous, circular opening reduces the risk of radial tears (that can extend to the posterior capsule) and therefore phacoemulsification of the nucleus can be carried out in the capsular bag.1,2 Capsulorrhexis produces a continuous, circular opening that is also resistant and elastic, preserving the integrity of the capsular bag well and allowing the surgeon to perform phacoemulsification in an area that is partially isolated from other ocular structures.3 Hydrodissection of the lens and hydrodelineation of the nucleus can be safely performed. The elastic forces of the capsular tissue make the borders of capsulorrhexis resistant even to quite strong traction and manipulation. Stress in the zonular areas is very limited and the turbulence produced by phacoemulsification is mainly limited to the capsule’s interior, only marginally affecting other eye tissues.4 CCC makes the cortex irrigation/aspiration step easier because of the so-called C letter profile that is formed and that provides a good separation between the anterior and posterior capsular surface. The irrigation/aspiration probe captures the cortical material without risk of tearing the posterior capsule.5 With CCC, the artificial lens can be centered better and, if rupture of the posterior capsule occurs, it can provide adequate support to the artificial lens positioned in the sulcus. Compared with previously used techniques, CCC has advantages in postoperative conditions as well. The even distribution of forces inside ensures the artificial lens is correctly positioned and remains centered and stable in time—this is particularly important when it is necessary to implant a toric and bifocal lens, which is heavily dependent on stability and immobility to work properly.

The large contact area between the loops of the artificial lens and the capsule reduces the risk of lens decentration. Finally, CCC reduces the possibility of contact between the intraocular lens (IOL) and the iris and ciliary bodies, reducing the risk of inflammation, hyphema, or dispersion of the iris pigment. The risk of synechiae between the iris and lens is reduced because there are no anterior capsule remnants that can adhere to the pupil, causing pupil distortion or pupillary block. A fundamental physical principle in the execution of capsulorrhexis is that an increase in vitreous pressure that determines an anterior push on the lens causes radial tension in the zonular fibers that is transmitted to the anterior capsule. In these conditions, an incision in the anterior capsule tends to spontaneously move toward the lens equator. The more peripheral the capsule incision, the more marked is this tendency. What can be deduced from this physical principle is that, during capsulotomy, the anterior chamber must be adequately shaped and any vitreous pressure must be counterbalanced by using a viscoelastic substance (preferably one with high molecular weight). If the capsulorrhexis tends to escape, viscoelastic material must be repeatedly injected and the capsule must be opened with great caution. Capsulorrhexis, which can be performed with various instruments, creates a continuous capsulotomy. A cystotome or a pair of specific forceps can be used.6

CYSTOTOME TECHNIQUE In the cystotome technique,7 a 25-gauge insulin needle is generally used. A strong needle holder is used to bend the tip,

- 65 -

Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 65-73). © 2014 SLACK Incorporated.

66  Chapter 11

Figure 11-1. First step of the incision of the anterior capsule with a cystotome.

Figure 11-3. The tip of the flap that is created is lifted with the cystotome and pulled with a circular motion.

creating a 45-degree angle (approximately). Alternatively, a pre-packaged cystotome can be used. The cystotome must always enter in the presence of viscoelastic material, either through the main incision or the side-port incision (in which case, the surgeon must be very experienced, having great dexterity). The capsule is cut in a central area of the upper hemifield (Figure 11-1), directing the cystotome radially toward 2 to 3 o’clock. The length of the cut is the length of the radius of the planned circular capsulotomy.

Figure 11-2. The cystotome is turned, so it has a lateral-superior or lateral-inferior orientation.

Beginning inside the circle, you are planning to make means reducing zonular tension, making the creation of the anterior capsule flap easier (Figure 11-2). Joining the final part of capsulorrhexis with the starting part is easier as well. When the desired peripheral limit is reached, the cystotome is turned, so it has a lateral-superior or lateral-inferior orientation (depending on whether the circle was cut clockwise or counterclockwise), with a direction parallel to the pupillary edge, delicately lifting the anterior capsule at the same time. In this way, a small, roughly triangular flap of anterior capsule is created and can be folded onto the intact anterior capsule underneath (Figure 11-3). In this step, it is important to have good corneal transparency, a good pupillary red reflex, and a sufficiently high magnification to be able to appreciate the edges of the anterior capsule. Additionally—as in every step of capsulorrhexis—there must be no posterior pressure pushing the lens, and the zonular fibers must be adequately relaxed.8 The flap formed this way is picked by the cystotome near the apex and stretched with a circular movement in order to perform a continuous, regular capsulotomy (Figure 11-4). After a stretch of about 40 to 50 degrees, the distal end of the flap is released and the proximal part is grasped by the cystotome near the capsular opening point. The folded part of the previously opened anterior capsule is well controlled so that the capsulotomy can be extended (Figure 11-5). In general, six to eight maneuvers are enough to complete the circle and join the two sides of the flap in the most even way possible, connecting the last part of the capsulorrhexis with the first, from outside to inside (Figure 11-6).

Capsulorrhexis  67

Figure 11-4. A continuous, regular capsulotomy is performed this way.

Figure 11-5. The folded part of the previously opened anterior capsule is well controlled so the capsulotomy can be extended.

Figure 11-6. It generally takes 6 to 8 steps to complete the circle and the two sides of the flap can be joined in the most even way possible, connecting the last part of the capsulorrhexis with the first, from outside to inside.

Figure 11-7. The anterior capsule is opened using the sharp tips of Utrata forceps.

FORCEPS TECHNIQUE If forceps with blunt tips are used, the initial step of flap creation is usually performed with a cystotome, as described previously. If forceps with sharp tips are used (Utrata forceps), the initial incision is performed

directly with the forceps used to extend the capsulorrhexis (Figure 11-7). The forceps must lift the flap slightly to obtain a moderately centripetal movement (Figure 11-8). It is necessary to grasp the flap several times (generally every 45 to 50 degrees), to have an effective action without causing traction, directing the capsulorrhexis in the desired direction (Figure 11-9). In the forceps technique, performing the capsulotomy under the incision is a delicate point because

68  Chapter 11

Figure 11-8. The forceps must be given a centripetal movement to obtain a circular, regular opening.

Figure 11-9. It is necessary to pick up the flap several times (generally every 45 to 50 degrees), to have an effective action without causing traction, directing the capsulorrhexis in the desired direction.

Figure 11-10. In the forceps technique, performing capsulotomy under the incision is a delicate point because the width of the tips limits visibility. The forceps must therefore be tilted sideways, lifting the flap and moving it toward the center of the pupillary field in order to have the best view of the edge of the ongoing capsulotomy.

Figure 11-11. The same precautionary measures must be taken when the two extremities of capsulorrhexis are connected, ending the circular opening. In this case, joining must be from outside to inside.

the width of the tips limits visibility. The forceps must therefore be tilted sideways, lifting the flap and moving it toward the center of the pupillary field in order to see the edge of the ongoing capsulotomy (Figure 11-10). The same precautionary measures must be taken when the two

extremities of capsulorrhexis are connected, ending the circular opening. In this case as well, joining must be from outside to inside (Figure 11-11). Special coaxial forceps for capsulorrhexis are currently available. These very fine forceps have a sharp tip to

Capsulorrhexis  69

Figure 11-12. Put the cystotome’s tip in the middle of the nucleus and move it to the cortex.

perform the incision of the anterior capsule and create the starting flap of the capsulorrhexis. The considerable advantage of these forceps is that access to the anterior chamber is possible through the side-port incisions as well. As the incisions are smaller, the surgeon can keep the depth of the anterior chamber more stable, especially if the patient is not very cooperative or the eye is surgically challenging. Additionally, using forceps with a sharp tip is a way of reducing the number of surgical instruments entering into the anterior chamber.

CYSTOTOME AND FORCEPS TECHNIQUE A viscoelastic substance is required for this technique.9 A cystotome is used in the initial phase of the procedure, to cut the capsule starting from the center of the lens and moving outward. By sliding the back of the needle tip under the incision, the anterior capsule is lifted. A small triangular flap is created this way. Forceps can be used at this point (Figure 11-12). Gripping the extremity of the flap firmly, the capsule is opened clockwise or counterclockwise. In both cases, the traction force on the flap will have a centrifugal direction during the capsulorrhexis enlargement phase, alternated with a centripetal direction in the closing phase (Figure 11-13). It is important to try to keep the tip of the forceps parallel to the anterior capsule without lifting it much to reduce the risk of capsulorrhexis escape. As the capsulorrhexis approaches the main incision, great

Figure 11-13. In the forceps technique, during the capsule tear near the incision, it may be difficult to see the edge of the capsulorrhexis, so one must proceed carefully always creating a centripetal movement.

attention is required because the forceps hide the edge of the capsulorrhexis being performed. In this phase, it is useful to proceed very cautiously, pulling the capsulorrhexis flap toward the center of the lens without releasing it. After this point, if the flap is too long, it can be released and gripped nearer the opening edge of the capsulorrhexis.10 If the capsulorrhexis is too small, it can be enlarged, either in the initial phase of the operation or before/after the implantation of the IOL.11 Using curved coaxial scissors or Vannas scissors, an incision is made at the edge of the capsulorrhexis, recreating a flap. Using the capsulorrhexis forceps or coaxial forceps, the opening in the anterior capsule is enlarged. This procedure must be performed with great caution because the nearer the equator of the lens, the higher the risk of capsulorrhexis escape (caused by the stronger force exercised by the vitreous).12 If the cataract is particularly white and hard, the anterior capsule is not easy to see. In this case, dyes that enter the capsule, making it visible, can be used so that the execution of capsulorrhexis is easier. A 0.1% solution of methylene blue (trypan blue) is frequently used (Figure 11-14). It is introduced into the anterior chamber with a precise technique (Figure 11-15).13 To use the dye, an air bubble is injected into the anterior chamber and the dye is introduced next.13 In the presence of air, the dye distributes evenly on the anterior capsule and enters it (Figure 11-16). The anterior chamber is then washed with balanced salt solution (BSS) and, finally, the viscoelastic substance is introduced to flatten and stabilize the anterior capsule (Figure 11-17).

70  Chapter 11

A

Figure 11-15. Air is injected into the anterior chamber through a side-port incision so that the methylene blue distributes evenly on the anterior capsule.

B

Figure 11-16. The next step is the injection of methylene blue, which, by filling the anterior chamber, colors the anterior capsule of the opaque lens.

A C

B Figure 11-14. (A) If the cataract is particularly white and hard, the anterior capsule is not easy to see. In this case, dyes that coat the capsule making it visible can be used so that the execution of capsulorrhexis is easier. A 0.1% solution of methylene blue (trypan blue) is frequently used. (B, C) The anterior capsule colored with methylene blue is clearly visible; with the rhexis forceps, the surgeon opens the anterior capsule and creates a small flap; this is subsequently used to complete the rhexis.

Figure 11-17. (A) Injection of BSS for washing the anterior chamber, (B) followed by injection of viscoelastic substance to perform the capsulorrhexis.

Capsulorrhexis  71

Figure 11-18. At this point, the anterior capsule will be blue and the lens cortex white, so it appears very different from capsular tissue.

Figure 11-20. OCT image of the anterior capsule with the related pointers that indicate the area in which the laser will perform the cut. All anterior capsules must be included in the laser’s spatial range of action.

CCC can be performed at this point. The anterior capsule is blue and the lens cortex is white, so it appears very different from capsular tissue (Figure 11-18).

FEMTOLASER TECHNIQUE The femtosecond laser device has a software program to perform the capsulotomy. The size and centration of the capsulotomy are established by studying an OCT image that is acquired during the applanation of the patient’s

Figure 11-19. Image of an eye after treatment with a femtosecond laser for cataract surgery (LenSx, Alcon). The image on the monitor shows the eye with the projection of all the pointers in order to center capsulorrhexis, the fracture pattern of the cataract nucleus (cross or concentric circles), the site and dimensions of the side-port incisions, and the main incision.

Figure 11-21. OCT image of the laser beam’s action ranges in the cataract nucleus.

eye. The capsulotomy is centered with respect to the pupil and the patient’s visual axis using specific pointers on the obtained OCT image (Figure 11-19). Dimensions can also be precisely established. Next, the spatial interval that the anterior capsule of the lens involves is programmed. The laser will act in that area, performing a complete incision of the capsule (Figure 11-20). Using the foot pedal, the laser is activated and the capsulotomy is performed very quickly, with the profile chosen and programmed by the surgeon14 (Figures 11-21 and 11-22). After the anterior capsule has

72  Chapter 11

Figure 11-22. OCT image of the profile of the main corneal incision. The length, depth, profile, and site of the incision can be selected with the laser’s software.

Figure 11-23. Patient prepared for surgery with femtosecond laser. The incisions, capsulorrhexis, and nucleus fragmentation can be clearly seen.

important for a good outcome of surgery, especially if one of the latest-generation lenses is implanted (multifocal, accommodative) because these lenses are dependent on the characteristics of the capsulotomy to work correctly. Finally, a femtosecond laser capsulotomy does not cause tension or exert traction on zonular fibers, which automatically reduces the risk of capsulorrhexis escape or dislocation of the capsular bag. This is particularly relevant when dealing with patients who have congenital or traumainduced zonular fragility.

REFERENCES Figure 11-24. Complete and perfectly centered capsulotomy obtained with the femtolaser.

1.

2.

been cut, the patient is moved from the laser room to the operating room and prepared for surgery (Figure 11-23). The surgeon can insert a cystotome or coaxial capsulorrhexis forceps (not Utrata forceps) through the main or accessory incision and, with caution, remove the central button of the anterior capsule (Figure 11-24). To perform the capsulotomy correctly with a femtosecond laser, good docking is required and the surgeon must be familiar with the OCT images acquired by the instrument in order to obtain a complete, perfectly centered capsulotomy. If there is a mistake in the programmed energy or width of the interval the laser acts in, the capsulotomy may be incomplete and capsulorrhexis forceps will be required to complete it.15 The advantage offered by the femtosecond laser is to perform precise, perfectly circular capsulotomies, of a predetermined size, centered on the patient’s visual axis and on the center of the pupil. These last elements are crucially

3.

4.

5.

6.

7.

Parel JM, Ziebarth N, Denham D, et al. Assessment of the strength of minicapsulorhexes. J Cataract Refract Surg. 2006;32(8):13661373. Rahar S, Sethi H, Sethi H, Gupta VS. Needle capsulorrhexis in intumescent white cataract using slow injecting viscoelastic device through an anterior chamber maintainer. Nepal J Ophthalmol. 2011;3(2):214-215. Langwin ´ ska-Wos´ko E, Broniek-Kowalik K, Szulborski K. The impact of capsulorrhexis diameter, localization and shape on posterior capsule opacification. Med Sci Monit. 2011;17(10):CR577CR582. Kara N, Yazici AT, Bozkurt E, Yildirim Y, Demirok A, Yilmaz OF. Which procedure has more effect on macular thickness: primary posterior continuous capsulorrhexis (PPCC) combined with phacoemulsification or Nd:YAG laser capsulotomy? Int Ophthalmol. 2011;31(4):303-307. Ratnarajan G, Calladine D, Watson SL. Cross-action capsulorrhexis forceps for coaxial microincision cataract surgery. J Cataract Refract Surg. 2011;37(8):1559-1560. Kim EC, Hwang HS, Kim MS. Anterior capsular phimosis occluding the capsulorrhexis opening after cataract surgery in a diabetic patient with high hemoglobin A1C. Semin Ophthalmol. 2013;28(2):68-71. Kamal S. Anterior capsulorrhexis creation in modified capsular tension ring implantation. J Cataract Refract Surg. 2012;38(7):1303.

Capsulorrhexis  73 8.

Ruggiero J, Keller C, Porco T, Naseri A, Sretavan DW. Rabbit models for continuous curvilinear capsulorrhexis instruction. J Cataract Refract Surg. 2012;38(7):1266-1270. 9. Smith RJ, McCannel CA, Gordon LK, et al. Evaluating teaching methods of cataract surgery: validation of an evaluation tool for assessing surgical technique of capsulorrhexis. J Cataract Refract Surg. 2012;38(5):799-806. 10. Malik KP, Goel R, Kamal S. Bimanual capsulorrhexis using Sinskey hook. Cont Lens Anterior Eye. 2012;35(5):228-229. 11. Muralidhar R, Siddalinga Swamy GS, Vijayalakshmi P. Completion rates of anterior and posterior continuous curvilinear capsulorrhexis in pediatric cataract surgery for surgery performed by trainee surgeons with the use of a low-cost viscoelastic. Indian J Ophthalmol. 2012;60(2):144-146.

12. Jaber R, Werner L, Fuller S, et al. Comparison of capsulorrhexis resistance to tearing with and without trypan blue dye using a mechanized tensile strength model. J Cataract Refract Surg. 2012;38(3):507-512. 13. Leydolt C, Menapace R, Stifter EM, Prinz A, Neumayer T. Effect of primary posterior continuous curvilinear capsulorrhexis with posterior optic buttonholing on pilocarpine-induced IOL shift. J Cataract Refract Surg. 2012;38(11):1895-1901. 14. Auffarth GU, Reddy KP, Ritter R, Holzer MP, Rabsilber TM. Comparison of the maximum applicable stretch force after femtosecond laser-assisted and manual anterior capsulotomy. J Cataract Refract Surg. 2013;39(1):105-109. 15. Carifi G, Zuberbuhler B. Capsulorrhexis rescue techniques. J Cataract Refract Surg. 2012;38(10):1874-1875.

12 Hydrodissection Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Hydrodissection is a very important step for the correct execution of phacoemulsification. It frees the nucleus inside the capsular bag, which, other than making maneuvers of the nucleus itself easier, prevents the capsule and the zonules from being affected by the actions performed on the nucleus1 (Figure 12-1). Technically, hydrodissection consists in injecting a variable amount of fluid (balanced salt solution [BSS]) just under the anterior capsule through a blunt cannula connected to a syringe (Figure 12-2). The tip of the cannula is pushed forward into the most posterior position possible while injecting BBS (Figures 12-3 and 12-4). Great caution is required during this step in order to avoid causing irreparable damage to the capsule.2 The pressure put on the fluid and the effect of gravity cause the BSS to spread between the cortical material and the epinucleus (Figure 12-5). During this procedure, the fluid wave front separating the cortical material from the nucleus completely can be seen (Figure 12-6). This is a good sign (hydrodissection has occurred), but it does not mean that the established goal has been achieved (ie, releasing the nucleus from its cortical-capsular adherences). There are various factors involved in successfully separating the nucleus from the cortical material, such as age, cataract hardness, the degree of compactness of the nuclear lamellae, the type of cannula used, and so on. In some cases, it is impossible to obtain effective cleavage because the compact part of the nucleus involves almost all the lens.3 The main functions of hydrodissection are as follows: To mobilize the nucleus completely so that it can rotate freely inside the capsular bag (Figure 12-7)

●

To create room between the capsule and the nucleus for insertion of viscoelastic substance when intraoperative conditions require the nucleus to be brought into the pupillary plane or into the anterior chamber Hydrodelineation involves the separation (via fluid injection) of the central part of the nucleus from the compact internal nucleus or the nucleus from the epinuclear material (Figure 12-8). This step is performed after hydrodissection. A fine, blunt cannula is inserted into the anterior cortical material and in the epinucleus on the inner edge of capsulorrhexis and moved until resistance is found (ie, the harder part of the nucleus is reached). At this point, fluid is injected and it should create a cleavage between the nucleus proper and the epinucleus. When this occurs, a golden luminescent ring can be seen forming (golden ring) (Figure 12-9). Failure of the golden ring to appear after repeated injections of fluid means the nucleus is hard and compact. The hardness of the nucleus can also be assessed considering how easily (or not) the cannula enters the lens material. The functions of hydrodelineation are as follows: To separate the central nucleus from the external one

●

●

To allow the surgeon to assess the degree of hardness of the nucleus and how easy its emulsification is likely to be4

To release most of the capsular-cortical and corticalnuclear adhesions so that the removal of residual material is easier in irrigation/aspiration - 75 -

●

●

●

To be a crucial step in phacoemulsification techniques, which consider the emulsification of the central nucleus a distinct phase from the emulsification of the external epinucleus (in this way the epinucleus acts as a barrier protecting the posterior capsule and is possible only if the cataract nucleus is not particularly hard)

Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 75-78). © 2014 SLACK Incorporated.

76  Chapter 12

Figure 12-1. Hydrodissection frees the nucleus inside the capsular bag, which, other than making maneuvers on the nucleus itself easier, prevents the capsule and the zonules from being affected by the actions performed on the nucleus.

Figure 12-3. The tip of the cannula must be positioned under the anterior capsule and moved aiming to reach the nucleus equator, injecting BSS at the same time.

Figure 12-2. Example of a cannula used for cataract hydrodissection and hydrodelineation.

Figure 12-4. Injection of BSS with the hydrodissection cannula. The fluid distributes between the cortex and the posterior capsule and mobilizes the cataract nucleus.

Figure 12-5. The pressure put on the fluid and the effect of gravity cause the fluid to distribute between the cortex and the epinucleus.

Figure 12-6. Image of the wave of fluid passing between the cataract nucleus and the cortex.

Hydrodissection  77

Figure 12-7. With correct hydrodissection, the nucleus is completely mobilized and can be freely rotated in the capsular bag.

Figure 12-9. The golden ring: The bright effect is related to the liquid injected for the hydrodelineation between the nucleus and the cortex.

To allow the surgeon to evaluate the hardness of the nucleus by assessing how difficult it is for the cannula to penetrate between the cortical lamellae and especially by assessing how easily the BSS separates the lamellae After the fluid wave front during hydrodissection has passed and the formation of the golden ring with hydrodelineation occurs, it is good practice to rotate the cataract nucleus delicately to check that it is completely mobile. Nucleus rotation is performed using the same cannula used for hydrodissection. The cannula is placed gently into the nucleus and with a delicate maneuver it is rotated clockwise and/or counterclockwise so that the nucleus makes a 90- to 180-degree rotation. Extreme caution is required in this step so that excessive traction is not exerted on the zonules, especially if there is not absolute certainty that the various parts of the lens have been completely cleaved.5 Caution is also required when dealing with very soft cataracts because the cannula may be pushed right through and touch the posterior capsule. In this case—when the nucleus ●

Figure 12-8. Hydrodelineation is the separation (via fluid injection) of the central part of the nucleus from the compact internal nucleus or endonucleus from the epinucleus.

Figure 12-10. Tear in the posterior capsule at the point in which the posterior polar opacity adheres more tightly to the posterior capsule.

is particularly soft—it may help to prolapse the nucleus outside the capsular bag, luxating it into the anterior chamber, which reduces the chances of accidentally damaging the posterior capsule. When dealing with posterior subcapsular cataracts or congenital cataracts that have a “coin” adhering to the posterior capsule, hydrodissection must be performed with the utmost caution. It is preferable to perform only hydrodelineation because in these cases the posterior capsule often opens. If this occurs, it is important (and useful) to rapidly inject an adhesive viscoelastic substance to stop vitreous prolapse (Figure 12-10). Hydrodelineation alone can be used to remove the nucleus, leaving the posterior epinucleus in place, which prevents (or delays) the posterior capsule from opening. With capsulorrhexis escape, hydrodissection must be performed very slowly, injecting BSS in through the opposite side of escape and trying not to apply excessive traction on the peripheral areas of the capsule (to stop the laceration of capsulorrhexis from expanding further). Should this occur, great attention must be paid to ensure the nucleus does not exit from the capsular bag or capsulorrhexis or the opening will enlarge and possibly spread to the posterior capsule.6

78  Chapter 12

REFERENCES 1.

2.

3.

Gupta SK, Kumar A, Agarwal S, Agarwal S. Phacoemulsification without preoperative topical mydriatics: induction and sustainability of mydriasis with intracameral mydriatic solution. Indian Indian J Ophthalmol. 2013 Apr 10. Williams GS, Radwan M, Kadare S, Williams CP. The short to medium-term risks of intracameral phenylephrine. Middle East Afr J Ophthalmol. 2012;19(4):357-360. Lundqvist O, Behndig A. Posterior chamber injection of intracameral mydriatics increases the durability of the mydriatic response. Acta Ophthalmol. 2012 Sep 11.

4.

5.

6.

Lorente R, de Rojas V, Vázquez de Parga P, et al. Intracameral phenylephrine 1.5% for prophylaxis against intraoperative floppy iris syndrome: prospective, randomized fellow eye study. Ophthalmology. 2012;119(10):2053-2058. Bäckström G, Lundberg B, Behndig A. Intracameral acetylcholine effectively contracts pupils after dilatation with intracameral mydriatics. Acta Ophthalmol. 2013;91(2):123-126. Thaler S, Hofmann J, Bartz-Schmidt KU, Schuettauf F, Haritoglou C, Yoeruek E. Methyl blue and aniline blue versus patent blue and trypan blue as vital dyes in cataract surgery: capsule staining properties and cytotoxicity to human cultured corneal endothelial cells. J Cataract Refract Surg. 2011;37(6):1147-1153.

13 Intraocular Fluids Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Cataract surgery with phacoemulsification requires drugs and fluids for intraocular use, such as anesthetics, viscoelastic substances, balanced salt solution (BSS) for hydrodissection, hydrodelineation and hydration of incisions, adrenaline to dilate the pupil in the case of intraoperative miosis, and antibiotics to inject at the end of the operation. Viscoelastic substances were discussed in Chapter 10.

IRRIGATION FLUIDS The purpose of irrigating solutions is to keep the anterior chamber stable during cataract fracturing and fragmentation, to cool the tip of the ultrasound handpiece, and to aspirate the emulsified fragments out of the eye. The first irrigating solutions used in cataract surgery were saline solution, lactated Ringer solution, and plasmalyte 148.1 Later, in 1960, saline solutions with ion composition, pH, and osmolarity more similar to that of the aqueous humor were developed. They were called BSS.2 In 1973, a third generation of saline solutions (BSS Plus) was developed after studies in which the addition of glutathione, glucose, and bicarbonate to the BSS was shown to contribute to better preservation of corneal endothelial cells in vitro.3–5 Studies comparing the effects of using lactated Ringer solution and BSS Plus showed that, in patients in the Ringer solution group, there was more decrease in the density of endothelial cells if phacoemulsification was prolonged or large volumes of irrigating solutions were used, compared to identical cases in which BSS Plus was used.1,2 The

behavior of lactated Ringer solution is therefore similar to BSS in simple cataract operations, whereas in complex cases, BSS Plus should be used. Lactated Ringer solution is a hypotonic (260 mOsm) saline solution that is slightly more acidic (pH 6.4) than aqueous. It contains sodium chloride, potassium chloride, calcium chloride, and lactate ions. BSS contains sodium chloride, calcium chloride, magnesium chloride, sodium acetate, and sodium citrate. It is transparent, does not leave residues, is isotonic with ocular tissues, and the various solutes do not interfere with normal cellular metabolism. Unlike normal saline solutions, BSS is very similar to aqueous and protects tissues more effectively. Because the solution is isotonic, good transparency of the corneal tissue is ensured during surgery. BBS Plus is a saline solution enriched with glucose, sodium bicarbonate, and glutathione. Its pH (7.4) and osmolarity (305 mOsm) are very similar to those of aqueous. Glutathione (GSH and GSSG) is a natural antioxidant. During intraocular surgery, tissue cells release many free radicals that can damage the tissues’ cellular functions. Glutathione is an excellent antioxidant that binds free radicals and, through an oxidization process, eliminates them. It preserves the integrity of the junctional complexes of endothelial cells6 and of the intraocular blood–aqueous barrier.7 Intraocular tissues are particularly sensitive to reduced levels of intracellular glutathione. Glutathione depletion can trigger cellular apoptosis.8 Sodium bicarbonate is one of the elements that make up the buffering system in tissue cells to maintain cellular pH balance. It is the main component of the aqueous and it is crucially important for maintenance of the blood–aqueous barrier

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80  Chapter 13 and to keep retinal cells working. Some studies have shown that a reduction in sodium bicarbonate creates a reduction in light-induced ERG-evoked potentials9 and in the metabolism of isolated rat retinal cells.10 Glucose is the main source of energy used by cells to work. It helps keep the cornea and lens transparent and it is crucial for retinal cells to work properly. A reduction in cellular glucose causes rapid deterioration of endothelial and retinal cells. Finally, magnesium is essential for the function of the Mg-ATPase pump of endothelial cells. The use of BSS Plus is associated with reduced corneal edema and a higher percentage of hexagonal cells 2 to 7 days after surgery,11 which means it protects the corneal endothelium, keeping cellular pleomorphism and polymegethism to a minimum after a short or long irrigation of the anterior segment, unlike BSS.12 The use of BSS Plus is recommended during all cataract operations that are particularly complicated and long in order to ensure the intraocular tissues are better protected during surgical maneuvers. BSS and BSS Plus have been shown to act in a similar way in noncomplex cataract operations. The temperature of the intraocular irrigating solutions (BSS, BSS Plus) must be about 23°C (the temperature of the operating room). Some authors have shown that lower temperatures do not have any beneficial effects in reducing the risk of damage to endothelial cells.13 BSS bottles must be changed at the end of every operation and must be stored in the refrigerator to make full use of the ability to cool the tip of the phaco handpiece. The solutions used for irrigation of the anterior segment must have very specific characteristics so that intraocular tissues are not damaged and there is no induction of dangerous, toxic inflammatory reactions (toxic anterior segment syndrome [TASS]). TASS is an acute, noninfectious inflammatory process that appears in the early hours following surgery and generally clears rapidly with topical treatment with steroids. The inflammation appears within 12 to 72 hours after cataract surgery or other open-eye operations of the anterior segment, which is the only area involved. Bacterial cultures are negative. Damage mainly affects the corneal endothelium. Corneal edema spreads from limbus to limbus and deposits of fibrin and hypopyon are present. The pupil does not react and damage to the trabecular meshwork may cause ocular hypertension. Vision is usually clouded and there may be no pain.14 The causes of TASS are many and difficult to identify. The best known causes include the preservatives in ophthalmic solutions, denatured viscoelastic materials, bacterial endotoxins, and intraocular lenses.15 The incidence of TASS varies between 0.1% and 2% and it is mainly caused by toxicity phenomena (and less by lack of sterility). Treatment must be started very soon with topical steroids administered once an hour.

DRUGS ADDED TO THE INTRAOCULAR IRRIGATING SOLUTIONS Anesthetics Phacoemulsification with topical anesthesia requires the injection of anesthetic into the anterior chamber, before the viscoelastic substance is injected, to improve the analgesic effect.16 The anesthetic must not contain preservatives and the pH of the solution in which it is dissolved must be compatible with the pH of the living cells in the tissues of the anterior segment. The most commonly used product is preservative-free 1% lidocaine hydrochloride, which is injected into the anterior chamber through a 30-gauge cannula. Lidocaine hydrochloride (1%) has been shown to have no toxic effects on the cells of the corneal endothelium because of its neutral pH and it has an excellent analgesic effect.17 A 1% lidocaine solution with epinephrine can be administered to patients taking medication for prostatic hyperplasia and who are suspected to develop intraoperative floppy iris syndrome. In this way—as shown by the studies carried out by Dr. Joel K. Shugar18—good analgesia and excellent pupil dilation can be obtained, especially if few drops of 1% tropicamide are instilled before the operation. This solution is called Epi-Shugarcaine19 (Table 13-1).

Mydriatic Drugs Despite good preoperative dilation obtained by combining a mydriatic drug with a nonsteroidal anti-inflammatory compound, mydriasis reduction may occur (possibly even varying degrees of miosis) during surgery, especially if the operation lasts a long time and there are many maneuvers in the eye. This reaction may depend on a number of factors such as the photomotor reflex in response to the intense illumination from the microscope, the effect of general anesthetics, and the local release of messenger molecules following mechanical tissue stimulation. Miosis induced by mechanical irritation (caused by instruments rubbing or by the turbulence of intraocular liquids) is not linked to sympathetic or parasympathetic innervation, so it cannot be prevented by parasympatholytic agents. However, sympathomimetic agents have a postsynaptic action on the pupil-dilating muscles, so they can be used to correct intraoperative miosis. The main drug used for this purpose is adrenaline, which is diluted in the irrigating solution. It is important to prepare a 1:10,000 dilution and use a preservative-free product to avoid toxic effects on intraocular tissues, especially on the corneal endothelium. Normally, 1 mL of preservative-free 0.025% adrenaline (0.25 mg per 250 cm³ of solution) is diluted in the irrigating solution.

Intraocular Fluids  81

TABLE 13-1.

PREPARATION OF EPI-SHUGARCAINE 9 cc BSS Plus + 3 cc preservative-free 4% lidocaine + 4 cc 1:1000 epinephrine w/o bisulfite Or Dilute 1 cc preservative-free 4% lidocaine in 3 cc BSS Plus, discard 1 cc, and add 1 cc 1:1000 epinephrine w/o bisulfite

Miotics At the end of cataract surgery, the injection of miotic drugs may sometimes be necessary. Miosis at the end of surgery may be needed to check if there are vitreous strands in the anterior chamber that are altering the shape of the pupil or to check if, after implantation in the sulcus, the haptics are adhering to the posterior surface of the iris and are altering normal pupillary motility. The most commonly used drug is acetylcholine chloride. Acetylcholine chloride (Miovisin or Miochol-E) is a powder and it must be appropriately diluted in water for injectable solutions. It works rapidly and causes the immediate contraction of the ciliary muscle, which causes pupillary miosis. It is also rapidly hydrolyzed by the cholinesterase in the cells of the tissues in the anterior chamber, so the duration of its action is limited.

Vital Dyes Trypan blue 0.1% (vision blue) is an isotonic vital dye that is not phototoxic at normal tissue pH. During cataract surgery, it is used to color the anterior capsule before performing capsulorrhexis20 should there not be a good red reflex (as with hypermature cataracts or hyperpigmentation of the ocular fundus). The dye solution is normally injected through a 30-gauge cannula needle after injecting a bubble of air in the anterior chamber. The air allows the dye to spread evenly, coloring the surface of the anterior capsule completely. The dye is later removed by injecting BSS. Methylene blue is a vital dye used to improve the visualization of the anterior capsule of the lens. It is used if the cataracts are white and very mature, in the absence of red reflex and hard cataracts, or in conditions of corneal opacity or retinal abnormalities alter the red reflex. The dye is also required if posterior capsulotomy is performed or when the surgeon is training in phacoemulsification and has not completely mastered the skill of capsulorrhexis. By using this dye, the anterior capsule of the lens can be made clearly visible, making the execution of capsulorrhexis easier and safer.

Air Air is another important element that can be injected into the anterior chamber. It can be useful in many steps of cataract surgery. As mentioned previously, it is required before the injection of the vital dye during capsulorrhexis. It is useful at the end of surgery to check for dehiscence of surgical wounds or to identify small vitreous strands adhering to the surgical wound. During surgery, an air bubble can be injected if secondary anterior vitrectomy is required because capsular rupture has occurred. Thanks to the “pushing” effect of the bubble, the vitreous is kept in the posterior chamber, reducing the risk of vitreous in the anterior chamber. An air bubble can be useful to reattach Descemet’s membrane with partial or extensive detachment of the membrane. Finally, some studies in animals have shown that the presence of an air bubble in the anterior chamber (injected at the end of surgery) can have a protective effect against endophthalmitis induced by Staphylococcus epidermidis.21

REFERENCES 1.

Lucena DV, Ribeiro MSA, Messias A, Bicas HEA, Scott IU, Jorge R. Comparison of corneal changes after phacoemulsification using BSS Plus versus lactated Ringer’s irrigating solution: a prospective randomised trial. Br J Ophthalmol. 2011;95(4):485-489. 2. Merrill DL, Fleming TC, Girard LJ. The effects of physiologic balanced salt solutions and normal saline on intraocular and extraocular tissues. Am J Ophthalmol. 1960;49:895. 3. McCarey BE, Edelhauser HF, Van Horn DL. Functional and structural changes in the corneal endothelium during in vitro perfusion. Invest Ophthalmol. 1973;12:410-417. 4. Edelhauser HF, Gonnering R, Van Horn DL. Intraocular irrigating solutions—a comparative study of BSS Plus and lactated Ringer’s solution. Arch Ophthalmol. 1978;96:516-520. 5. Edelhauser HF, Van Horn DL, Hyndiuk RA, et al. Intraocular irrigating solutions. Their effect on the corneal endothelium. Arch Ophthalmol. 1975;93:648-657. 6. Araie M, Shirasawa E, Hikita M. Effect of oxidized glutathione on the barrier function of the corneale endothelium. Invest Ophth Vis Sci. 1988;29:1884-1887. 7. Araie M, Shirasawa E, Ohashi T. Intraocular irrigation solutions and permeabilità of the blood-aqueous barrier. Arch Ophthalmol. 1990;108:882-885. 8. Ghibelli L, Fanelli C, Rotilio G, et al. Rescue of cells from apoptosis by inhibition of active GSH extrusion. FASEB J. 1998;12:479-486. 9. Winkler BS, Simson V, Benner J. Importance of bicarbonate in retinal function. Invest Ophthalmol Vis Sci. 1977;16:766-768. 10. Winkler BS. Comparison of intraocular solution on glycolysis and levels of ATP and glutathione in the retina. J Cataract Refract Surg. 1988;14:633-637. 11. Glasser DB, Matsuda M, Ellis JG, Edelhauser HF. Effects of intraocular irrigating salutions on the corneal endothelium after in vivo anterior chamber irrigation. Am J Ophthalmol. 1985;99:321-328. 12. Sarobe Carricas M, Segrelles Bellmunt G, jimenez Lasanta L, Iruin Sanz A. Toxic anterior segment syndrome (TASS) studying an outbreak. Farm Hosp. 2008;32(6):339-343.

82  Chapter 13 13. Praveen MR, Vasavada AR, Shah R, Vasavada VA. Effect of room temperature and cooled intraocular irrigating solution on the cornea and anterior segment inflammation after phacoemulsification: a randomized clinical trial. Eye. 2009; 23(5):1158-1163. 14. Cornut PL, Chiquet C. Toxic anterior segment syndrome. J Fr Ophtalmol. 2011;34(1):58-62. 15. Cutler Peck CM, Brubaker J, Clouser S, Danford C, Edelhauser HE, Mamalis N. Toxic anterior syndrome: common causes. J Cataract Refract Surg. 2010;36(7):1073-1080. 16. Carino NS, Slomovic AR, Chung F, Marcovich AL. Topical tetracaine versus topical tetracaine plus intracameral lidocaine for cataract surgery. J Cataract Refract Surg. 1998;24(12):1602-1608.

17. Blanco MR, Jaramillo R, Arroyo LL, Lozano J. Intracamerular anesthesia in cataract surgery. Invest Ophthalmol Vis Sci. 2002;43-46. 18. Shugar JK. Use of epinephrine for IFIS prophylaxis. J Cataract Refract Surg. 2006;32 (7):1074-1075. 19. Shugar JK. Intracameral epinephrine for IFIS prophylaxis. Cataract Refract Surg Today. 2006;6(9):72-74. 20. Smith EF, Desai RU, Schrier A, Enriquez B, Purewal BK. Trypan blue capsulorrhexis. Ophthalmology. 2010;117(7):1462-1462.e1. 21. Mehdizadeh M, Rahat F, Khalili MR, Ahmadi F. Effect of anterior chamber air bubble on prevention of experimental Staphylococcus epidermidis endophthalmitis. Graefes Arch Clin Exp Ophthalmol. 2010;248(2):277-281.

14 Refractive Cataract Surgery Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD The expression refractive cataract surgery is a relatively new concept. It describes the fusion or combination of traditional cataract surgery with modern techniques of refractive surgery.1 In the past, the aim of cataract surgery was purely medical and its purpose was to restore good vision after a period in which vision was reduced by the formation (and progression) of opacity of the lens.2 Cataract surgery was performed when due to the progressive loss of transparency (clouding) of the lens, the patient became blind or had problems performing simple, ordinary everyday tasks, such as reading a newspaper or driving. Today, cataract surgery has evolved into a new role—it is not just performed to restore vision, it is also used to correct previously existing refractive errors, improve visual quality, and correct presbyopia, thus reducing or eliminating the need for glasses when reading or driving. The change in the indications for cataract surgery and its performance has been affected by the improvement and simplification of the surgical technique and by the development of tools that allow surgeons and patients to obtain good, satisfying results.3 The introduction of new artificial lenses (called advanced technology [AT] or premium intraocular lenses [IOLs]) was the key to the development of refractive cataract surgery.4 These latest-generation lenses can, after surgery, provide good visual acuity without requiring correction at almost all distances, eliminating or reducing the need for reading glasses. There is now a broader range of monofocal artificial lenses with different dioptric powers. The power range is high and can correct very high levels of myopia and hyperopia.

Aspheric lenses have been introduced. Traditional monofocal lenses have spherical aberration that causes a slight peripheral image distortion, especially when the pupil dilates in response to poor light conditions, which causes loss of vision quality. Aspheric lenses correct this small distortion, restoring the best quality to perceived images. Aspheric lenses minimize corneal spherical aberrations and improve contrast sensitivity, which means they provide better quality vision especially in the case of medium-large pupils. With these lenses, detail perception is increased, particularly in critical light conditions (fog, at night in closed environments and when driving). In young patients, the negative spherical aberration of the lens and the positive spherical aberration of the cornea create a total nominal aberration.5 Negative spherical aberration increases with age and so does the positive aberration induced by the lens. These variations contribute to patients having reduced quantity and quality of vision.6 Over the years, studies performed on the vision quality of patients who underwent cataract surgery with the implantation of an artificial lens demonstrated that patients who received an artificial lens suffered from a decrease of visual quality compared with patients with a natural lens.7 Aspheric artificial lenses are built in such a way that they can add negative aberration to the total optical system, thus reducing total spherical aberration. This principle allows better contrast sensitivity and a reduction in glares and halos. The latest-generation lenses are aspheric, toric, and/or multifocal and so can offer patients improved visual quality in every way, reducing image distortion and halos, correcting preexisting astigmatism, and restoring distance vision

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84  Chapter 14 (without the need for glasses) as well as intermediate and near vision. The introduction of pseudophakic artificial lenses with high negative power means, among other things, that the refractive error can be corrected in very myopic patients to clear lenses—as long as they are old enough to have presbyopia (especially if contact lenses are no longer tolerated and glasses do not correct the refractive error well enough). These lenses are also useful when correction with excimer laser or surgery with phakic lenses cannot ensure a precise, definite result. Patients with high amounts of hyperopia can undergo cataract surgery and have an artificial lens implanted and their refractive error corrected, obtaining an improvement in their visual quality. In the case of closedangle glaucoma risk, the extraction of the transparent lens can be very useful and recommended.8 Listed next are the AT IOLs or premium IOLs used in cataract refractive surgery. Toric IOLs are artificial lenses that correct astigmatism. About 20% of patients undergoing cataract surgery have a clinically significant level of astigmatism. To obtain emmetropia in these patients, the surgeon can choose between two options: combining cataract surgery and the implantation of a monofocal lens with corneal refractive surgery or implanting a toric artificial lens. Some toric lenses are made of hydrophobic acrylic material and the toric element is present on the posterior surface of the optic. At the level of the lens, there is a mark with two or three peripheral points or a peripheral score that indicates the axis of the lens’s cylinder. When the lens is positioned in the capsular bag, the score must coincide with the mark previously made.9 The power of the toric lens varies depending on the model of artificial lens chosen and can correct up to 6 diopters. The success of implantation of a toric lens is related to the accuracy of the lens power and to its correct positioning in the capsular bag. Lens manufacturers provide surgeons with software that, using the keratometry and biometry of the patient, calculates the power of the lens required to obtain emmetropia. A picture of the position of the lens inside the capsular bag is also provided. To date, however, correct positioning of the lens is still the major hurdle for the success of the operation.10 Some studies have shown that one of the reasons toric lenses fail may be the rotation of the lenses inside the capsular bag (caused by the sac’s fibrosis reaction).11 In general, this event occurs within a month from surgery and it has been shown that even a 10-degree rotation causes a 35% reduction in the corrective power of the lens. The astigmatic correction power of a toric lens vanishes completely with a 30-degree rotation.12 If good and satisfactory refractive postoperative results are to be achieved, it is crucially important that surgery is performed accurately and scrupulously, that the capsulorrhexis size is adequate,13 that the capsular bag is cleaned completely and accurately, and, lastly, that only a minimal amount of

Figure 14-1. Buratto’s corneal marker for slit lamps and toric lenses. This marker is mounted on the slit lamp’s tonometer support and can be used to mark the 0- and 180-degree axes. (Reprinted with permission of Janach.)

viscoelastic substance is left in the capsular bag because it could change the final position of the lens. It is just as important that, before the operation, the axis of astigmatism is precisely identified and exactly marked during the slit lamp examination14 (Figure 14-1). ORA (WaveTec) laser interferometry used intraoperatively has also allowed more correct power choice and alignment of toric lenses. Residual postoperative astigmatism is the main reason patients undergoing cataract surgery must wear distance vision glasses. The possibility of using a toric artificial lens reduces—and can eliminate—the need to use glasses after surgery. High levels of astigmatism in patients who cannot wear contact lenses (or whose refractive error cannot be properly corrected by them) can be corrected by using toric artificial lenses. These kinds of lenses also offer better visual quality to patients with keratoconus whose condition has been stable for a few years and whose refractive error caused by the corneal deformation is causing poor vision quality. In the case of patients with keratoconus and cataract, the removal of the clouded lens and the correction (at least partial) of the preexisting refractive error result in an improvement of vision, which provides considerable advantages in terms

Refractive Cataract Surgery  85 of visual quality. However, for this to occur, astigmatism must not be too asymmetrical or excessively irregular. Accommodative and multifocal IOLs are artificial lenses that use a different mechanism to correct presbyopia and reduce (or eliminate) the need for glasses. Multifocal IOLs and accommodative lenses allow patients to carry out almost every ordinary daily activity (such as driving or reading a newspaper) without using glasses. Today the demand to correct presbyopia is rising because the importance of intermediate and near vision is increasing. The daily use of mobile phones, laptops, tablets, palmtops, and so on requires good near vision (about 30 cm), so the development of presbyopia is problematic, especially in emmetropic patients who have never used glasses and who find themselves forced into a never-ending glasses-on glasses-off routine in order to read or type. The need to change this condition, the wish to improve vision in every situation in which reading is required, and the desire to restore the natural, multifocal condition of the eye have led to the development of accommodative and multifocal artificial lenses. With these lenses, it is possible to focus at various reading distances without requiring glasses all the time. Cataract surgery with multifocal and accommodative lenses means reading glasses may not be necessary except in conditions of poor light.15 There are three kinds of artificial lenses for the correction of presbyopia—diffractive, refractive, and accommodative. The characteristic of diffractive artificial lenses is that the anterior curvature of the lens is used to correct distance vision. The posterior surface of the artificial lens has tiered concentric rings that use the physical principle of diffraction to create a more anterior, second focal point for near vision. The surface of lenses was, a few years ago, improved with apodized optics. The diffractive steps are built with a precise reduction in height from the center to the periphery. The characteristics of this type of artificial lenses are listed next. They provide good distance and near vision, but fair intermediate vision. Regarding the model of the IOL, there is an addition +4, +3, +2.5, or +1.5. ●

●

They are preferable in the dominant eye.

They are minimally affected by the diameter of the pupil. The anterior surface of refractive artificial lenses has annular zones of different curvature. They use the physical principle of refraction to create focal points for distance vision, intermediate vision, and near vision. Their features are listed next. They provide good vision at intermediate distance. ●

●

●

●

They offer fair near vision (which is qualitatively not as good as that offered by diffractive lenses). They offer fair distance vision (which is qualitatively not as good as that offered by monofocal lenses).

They are affected by pupillary diameter and there can be problems especially driving at night. Patients with a large pupil have complained of seeing halos because of the concentric zone layout of the lens. Accommodative artificial lenses attempt to replicate the forward and backward movements caused by contraction and relaxation of the ciliary muscle. The haptics for fixing these lenses are very flexible and have “grooves” to allow the anteroposterior shift of the optic and to change the focus with a mechanism similar to the natural mechanism. They are less reliant on “neural adaptation” mechanisms and are not associated with dazzling, ghost images, and halos frequently reported with multifocal lenses. For these reasons, research is concentrating on accommodative lenses, and new models will probably be developed in the near future. Accommodative lenses generally provide excellent distance vision, but most patients require additional correction for near vision. The possibility of having highly performing lenses requires utmost precision in performance of the tests to calculate their power (such as keratometry and ultrasound biometry). Additionally, the site of the corneal incisions can positively affect the refractive result of the operation, so selecting the right site is crucial. Finally, it is very important to identify and carefully understand the patient’s needs and expectations in order to avoid disappointment. Cataract surgery with the femtosecond laser is the current final frontier of cataract refractive surgery.16 By using a femtosecond laser, certain steps of the surgical procedure that are linked to the surgeon’s experience and skill can be performed in a precise, reproducible manner. To realize their full potential, the increasingly performing artificial lenses described previously—which can offer visual quality bordering on perfection—require very precise, minimally invasive surgery that has no residual, iatrogenic refractive errors. The surgical steps that can cause disappointing postoperative refractive results (caused by the latest-generation artificial lens not working properly) are the corneal incisions, capsulorrhexis, phacoemulsification, and the cortex irrigation/aspiration. The execution of irregular incisions, with uneven and poorly self-sealing edges, causes changes in the tension forces in the corneal tissue, which causes postoperative astigmatism. Capsulorrhexis must be of the right size and have a regular—preferably circular—shape to allow the haptics of accommodative artificial lenses to move correctly and to reduce diffractive phenomena (halos and glares) in patients with multifocal artificial lenses.17 A perfectly centered capsulorrhexis allows the lens to be centered correctly. During phacoemulsification, maneuvers must be performed gently and the amount of ultrasound must be ●

86  Chapter 14

Figure 14-2. Femtosecond laser incisions.

limited to avoid damage to the corneal endothelium and corneal stroma, which could jeopardize postoperative visual quality. The use of large amounts of ultrasound in the presence of very hard cataracts increases the risk of accidental rupture of the posterior capsule, which makes the implantation of the artificial lens difficult. The correct and accurate execution of the cortex aspiration step and of cleaning the capsular bag makes positioning the artificial lens easier, especially with toric lenses. Today, the femtosecond laser can be used to perform some surgical steps of cataract surgery in a precise, standardized, and reproducible manner. The surgical steps in which the femtosecond laser can be used are as follows: Corneal incisions ●

●

Capsulotomy

●

The fragmentation of the cataract nucleus

CORNEAL INCISIONS To begin with, the femtosecond laser can perform corneal incisions with a precise shape, length, and depth, reducing the risk of inducing postoperative astigmatism. Because of the reproducibility and repeatability of the laser, incisions are always precise and identical, allowing the surgeon to standardize the procedure and to obtain refractive results ever closer to perfection. The precision of the incisions prevents them from being excessively “stressed” during surgical maneuvers and ensuring instruments pass through them easily. The possibility of creating a perfect shape with the laser means that it is easy to obtain selfsealing incisions, without the risk of wound dehiscence at the end of surgery (thus reducing the risk of infection and endophthalmitis) (Figure 14-2). The femtosecond laser can be used to perform corneal relaxing incisions in order to correct the patient’s preoperative astigmatism. Because of the precision of the incision profile and depth, the site, and precise optic zone, astigmatism correction can be modulated to obtain the best

Figure 14-3. Capsulorrhexis performed with femtosecond laser.

refractive result. Femtosecond laser incisions are performed incredibly quick and cause little discomfort to the patient because the procedure is completely painless. This, combined with the fact that the globe is in a docked condition, reduces the risk of patient involuntary movements, which can cause the surgical corneal incisions to be imprecise.

CAPSULOTOMY This is certainly the most interesting aspect. The femtosecond laser performs a perfectly round capsulotomy of a pre-calibrated size, without causing traction to the zonules. The capsulotomy is perfectly centered on the pupil, and the optic center of the implanted artificial lens can be positioned at the exact center of the capsulorrhexis (Figure 14-3). All these aspects are, today, more important than ever because of the development of artificial lenses with better performance (that are increasingly better designed to offer close-to-perfect visual quality and acuity) that require surgeons to manage the capsulorrhexis with micrometer-level precision. If the capsulorrhexis is slightly decentered or has a large diameter, it can negatively affect the final refractive result because of tilt or decentration of the artificial lens. Femtosecond laser surgery—which delivers a capsulotomy with a very precise diameter required by new accommodative lenses to work properly—also allows less-experienced surgeons to perform a precise capsulorrhexis with limited risks. Better centration, precise size, and a perfectly circular capsulorrhexis mean that artificial lenses can be centered correctly, which is crucially important in the case of multifocal, toric, and accommodative lenses. To provide good refractive results, toric lenses must be positioned with a precise orientation in the capsular bag and must not rotate from the original position. The risk of this occurring is reduced with the execution of a wellcentered, perfectly round capsulotomy with a pre-established size. The features of a capsulotomy performed with the femtosecond laser are such that the risk of secondary

Refractive Cataract Surgery  87

Figure 14-4. Fragmentation with pre-chopper forceps.

Figure 14-5. Opening of the pre-chopper forceps.

THE FRAGMENTATION OF THE CATARACT NUCLEUS

Figure 14-6. Appearance of the cataract nucleus with cross opening.

opacity arising in the posterior capsule is reduced. The risk of anterior capsular phimosis and fibrosis is reduced as well. Femtosecond laser surgery is a new opportunity to perform the capsulotomy even in very complicated cases; for example, it can be used on patients with alterations in the zonules or pseudoexfoliation syndrome. Laser capsulotomy is possible outside the pseudoexfoliation area without applying traction and tension on the equatorial region of the peripheral capsule and the zonular apparatus. In this way, the risk of bag dislocation can be reduced. Last but not least is the fact that femtosecond laser surgery greatly reduces the risk of capsulotomy radial escape. This can occur during manual execution of capsulorrhexis for a number of reasons, for example, the surgeon is inexperienced, the capsule is very fragile, a low-molecular-weight viscoelastic substance is being used, the anterior chamber has not been filled with enough viscoelastic substance, or the patient moves accidentally. A laser capsulotomy is a completely painless procedure that is very rapidly executed. At the beginning of the surgery, the surgeon extracts the button of cut anterior capsule with a coaxial capsulorrhexis forceps or with a hook.

Phacofragmentation leads to a reduction in the number of steps required for emulsification of the lens, which in turn reduces the quantity of ultrasound needed and allows the patient to recover more quickly. Fragmenting the nucleus with the femtosecond laser reduces the risk of tears in the posterior capsule, which is something that can occur if phacoemulsification is performed manually. It is most likely to happen initially, when the central cross is made, before separating the cataract into quadrants. Furthermore, the time in which ultrasound is needed is considerably reduced when using femtosecond laser and the nucleus can sometimes be removed directly with a 0.5-aspiration probe alone. The nucleus emulsification phase is very short and the risk of burns or stress to the incision is almost nonexistent (Figures 14-4 to 14-6). The reduction in ultrasound phacoemulsification time for the removal of the nucleus and the limited invasiveness of the procedure are associated with a lower incidence and lower risk of damage to the corneal endothelium and the retina, also because there is shorter exposure to the microscope light (Figure 14-7). Reduced ultrasound time is also the main reason the incidence of postoperative damage to the anterior segment and the retina are reduced. The fragmentation of the nucleus with the femtosecond laser is useful in patients with very hard cataracts. The time for nucleus removal is reduced and so is the amount of ultrasound used for cataract removal; there are fewer intraocular manipulations and the risks associated with phacoemulsification are lowered. Patients experience no pain during the nuclear fragmentation phase. The time of the procedure depends on the hardness of the nucleus, but it is, in any case, very short.

88  Chapter 14

A B

Figure 14-7. Aspiration of the quadrants created with prechopper forceps. In this step, the amount of ultrasound used is very small.

C Figure 14-9. Capsulorrhexis forceps. (Reprinted with permission of Janach.)

EXECUTION TECHNIQUE The femtosecond laser device has an integrated OCT system that acquires an image of the eye after applanation. The image is rapidly captured and the images of the lens, cornea, capsule, and iris are projected onto it. The surgeon then programs the treatment to perform. The procedure includes capsulotomy, the main incision and side-port incisions, nuclear phacofragmentation, and relaxing incisions (if needed). The surgeon activates the laser, which performs nuclear fragmentation, capsulotomy, corneal incisions, and the previously programmed relaxing incisions in about 1 minute.

SURGICAL INSTRUMENTS REQUIRED FOR CATARACT SURGERY WITH THE FEMTOSECOND LASER ●

A bivalve speculum to expose the eye during docking

●

A spatula to open the corneal incisions (Figure 14-8)

●

●

Figure 14-8. Buratto spatula for incision opening. (Reprinted with permission of Janach.)

REFERENCES 1.

2.

3.

4.

5.

Forceps to strip the anterior capsule (Figures 14-9 and 14-10)

6.

Prechop (Figure 14-11)

7.

Berdeaux G, Meunier J, Arnould B, Viala-Danten M. Measuring benefits and patients’ satisfaction when glasses are not needed after cataract and presbyopia surgery: scoring and psychometric validation of the Freedom from Glasses Value Scale (FGVS). BMC Ophthalmol. 2010;10:15. Kissner A, Kohlhaas M, Spörl E, Pillunat LE. Corneal aberrations before and after corneal and corneoscleral small incision cataract surgery [article in German]. Klin Monbl Augenheilkd. 2007;224(2):95-100. Tabernero J, Piers P, Benito A, Redondo M, Artal P. Predicting the optical performance of eyes implanted with IOLs to correct spherical aberration. Invest Ophthalmol Vis Sci. 2006;47(10):4651-4658. Visser N, Bauer NJ, Nuijts RM. Residual astigmatism following toric intraocular lens implantation related to pupil size. J Refract Surg. 2012;28(10):729-732. Naranjo-Tackman R. How a femtosecond laser increases safety and precision in cataract surgery? Curr Opin Ophthalmol. 2011; 22(1):53-57. Lim DH, Han JC, Kim MH, Chung ES, Chung TY. Factors affecting near vision after monofocal intraocular lens implantation. J Refract Surg. 2013;29(3):200-204. Goel R, Kamal S, Kumar S, et al. Feasibility and complications between phacoemulsification and manual small incision surgery in subluxated cataract. J Ophthalmol. 2012;2012:205139.

Refractive Cataract Surgery  89

A

A

B

C

B

Figure 14-10. Buratto forceps for removing anterior capsule following femto rhexis. (Reprinted with permission of Janach.) 8. 9.

10.

11.

12. 13.

Rosen E. Cataract surgery is refractive surgery. J Cataract Refract Surg. 2012;38(2):191-192. Nagy ZZ, Kránitz K, Takacs A, Filkorn T, Gergely R, Knorz MC. Intraocular femtosecond laser use in traumatic cataracts following penetrating and blunt trauma. J Refract Surg. 2012;28(2):151-153. Moshirfar M, Churgin DS, Hsu M. Femtosecond laser-assisted cataract surgery: a current review. Middle East Afr J Ophthalmol. 2011;18(4):285-291. Kránitz K, Takacs A, Miháltz K, Kovács I, Knorz MC, Nagy ZZ. Femtosecond laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg. 2011;27(8):558-563. Friedman NJ, Palanker DV, Schuele G, et al. Femtosecond laser capsulotomy. J Cataract Refract Surg. 2011;37(7):1189-1198. Gimbel HV, Brucks M, Dardzhikova AA, Camoriano GD. Scleral fixation of a subluxated intraocular lens-capsular bag complex through a fibrotic continuous curvilinear capsulorrhexis. J Cataract Refract Surg. 2011;37(4):629-632.

Figure 14-11. (A) Buratto pre-chopper forceps for nucleofragmentation. (B) Detail of Buratto pre-chopper forceps. (Reprinted with permission of Janach.)

14. Tan DK, Aung T, Perera SA. Novel method of assessing delamination of the anterior lens capsule using spectral-domain optical coherence tomography. Clin Ophthalmol. 2012;6:945-948. 15. Sipos E, Stifter E, Menapace R. Patient satisfaction and postoperative pain with different postoperative therapy regimens after standardized cataract surgery: a randomized intraindividual comparison. Int Ophthalmol. 2011;31(6):453-460. 16. Ecsedy M, Miháltz K, Kovács I, Takács A, Filkorn T, Nagy ZZ. Effect of femtosecond laser cataract surgery on the macula. J Refract Surg. 2011;27(10):717-722. 17. Miháltz K, Knorz MC, Alió JL, et al. Internal aberrations and optical quality after femtosecond laser anterior capsulotomy in cataract surgery. J Refract Surg. 2011;27(10):711-716.

15 Prevention of Endophthalmitis Lucio Buratto, MD; Stephen F. Brint, MD, FACS; and Laura Sacchi, MD Endophthalmitis is an inflammatory reaction that occurs after microbial agents, bacteria, viruses, and occasionally parasites colonize the interior of the eye. It can be of endogenous origin (septicemia) or of exogenous origin (postsurgical, posttraumatic). In this case, microbial contamination can come from the surface of the eye or the open incision (wound), contaminated instruments, the intraocular lens (IOL), or foreign bodies in the eye.1 The onset, severity, and clinical progress of endophthalmitis are closely related to the origin of the infection, the virulence and quantity of injected pathogens, the immune state of the patient, and the time of diagnosis.2 In about 29% to 43% of cataract operations, there is contamination by the pathogens normally found on the surface of the eye without the development of endophthalmitis.3–5 The eye protection mechanisms known as “immune privilege of the eye”† are particularly efficient in the anterior chamber of the eye and act as a barrier that limits the inflammatory response.6,7 If the defensive barrier is damaged (eg, intraoperative rupture of the posterior capsule with vitreous loss), the risk of endophthalmitis is 14 times higher.8 Microbial endophthalmitis has three infection phases: an incubation phase, acceleration phase, and destructive phase.9 The duration of the first phase (incubation) is variable but is generally 16 to 18 hours, even for the most †NDA: The expression immune privilege of the eye was coined by Peter Medawar to describe the absence of immune response against allotransplants in the anterior chamber or the brain. Studies have shown that the immune privilege is more than a passive microenvironment with anatomical features that ensure the immunity of the organ—it has an active role in stimulating the immune system with biochemical mechanisms. What makes the system unique is the mechanism to protect foveal vision (author’s note).

virulent pathogens. The penetration of pathogens into the eye causes the aqueous barrier to break, which leads to the exudation of fibrin and the infiltration of neutrophil granulocytes.10 The incubation phase is closely related to the proliferation speed of the pathogens and to some of their specific features, such as the capacity to produce toxins. In the case of the most common pathogens (such as Staphylococcus epidermidis and Staphylococcus aureus), the peak of infiltration is seen 3 days after infection.11 In the case of a primary infection in the posterior chamber, inflammation of the anterior chamber is seen first, with a specific immune response (macrophages and lymphocytes in the vitreous chamber) developing on day 7. Just 3 days after the intraocular infection, antibodies specific for the pathogen can be isolated. Once activated, they react against the pathogen and eliminate it, which normally happens on day 10 postinfection. This means that laboratory cultures—if performed after day 10—may be negative, even if there is severe inflammatory disease in the eye. Furthermore, during the immune response against the pathogen, the cells involved release substances, such as cytokines, that act as inflammatory mediators and that have a destructive effect on intraocular tissues—so severe they can cause proliferative vitreoretinopathy12 and, in extreme cases, retinal tears.13 According to one hypothesis, after rupture of the posterior capsule, the pressure increase caused by the use of the phacoemulsification device can push the bacteria into the vitreous chamber, where they proliferate, causing a characteristic anterior vitritis.14 IOLs are a potential vector of infection. Different pathogens have different abilities to adhere to lenses; for example, S epidermis adheres more to polypropylene lenses than to

- 91 -

Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 91-96). © 2014 SLACK Incorporated.

92  Chapter 15 polymethyl methacrylate lenses.15,16 Staphylococci adhere less to heparin-coated lenses.17 Finally, some studies have shown that the implantation of IOLs through a sterile, preloaded injector reduces the chances of intraocular contamination.18

CLASSIFICATION The criteria used for the classification of endophthalmitis can be different. 1. Etiological ●

Bacterial endophthalmitis

●

Viral endophthalmitis

●

Fungal endophthalmitis

●

Protozoan endophthalmitis

●

Parasitic endophthalmitis

2. Route of access used by pathogens ●

●

Exogenous endophthalmitis (90% to 95% of cases)— postoperative (65% to 90%) and posttraumatic (3% to 30%)

immunocompromised patients, in whom surgery probably reactivates the virulence of the pathogen. Protozoans cause 0.1% to 0.4% cases of endophthalmitis especially in patients who wear contact lenses. Although they are not very frequent, these endophthalmitis cases are usually very serious with a poor outcome. About 12.5% to 20% of cases have been found to have polymicrobial origin.23 Postoperative exogenous endophthalmitis can be infectious or sterile—the Endophthalmitis Vitrectomy Study 24 has determined that in 17.9% of cases, the pathogen cannot be isolated. These cases are of postoperative intraocular damage in the absence of septic factors, which occur after prolonged or traumatic surgery. These episodes of pseudoendophthalmitis resolve within 10 to 15 days after starting therapy with anti-inflammatory drugs. In some cases, the origin of damage may be endogenous if it is possible to show that surgery has caused the reactivation of preexisting uveitis. The main sources of contamination causing septic postoperative endophthalmitis are the ocular surface (conjunctival sac, crypts of Fuchs, lacrimal ducts) and the skin and eye adnexa (eyelids, eyelashes).

Endogenous or metastatic endophthalmitis (5% to 10% of cases)

ETIOPATHOGENESIS

3. Clinical assessment ●

Acute endophthalmitis (80% of cases, onset no later than 6 weeks from surgery)

●

Subacute endophthalmitis

●

Chronic endophthalmitis

4. Degree of extension ●

Localized endophthalmitis

Diffuse endophthalmitis The most common forms of endophthalmitis are the infectious exogenous bacterial forms, which account for 62% of all forms.19 Unfortunately, the percentage of cases in which the causative agent can be identified is between 54.4% and 63%.20,21 The Endophthalmitis Vitrectomy Study has highlighted the populations of bacteria that are most involved in infectious endophthalmitis cases. In 94% of the cases, the microbial pathogens are gram-positive bacteria (S epidermidis, S aureus, Streptococcus pneumoniae, and Propionibacterium acnes), whereas in 6.5% of cases, gram-negative bacteria are involved (Pseudomonas aeruginosa, Proteus, Serratia, Enterobacteriaceae).24 According to some authors, up to 16% of infectious forms are of fungal origin and are caused by Candida albicans, whereas forms caused by Aspergilli are very rare. The role of viruses in the development of endophthalmitis has not been fully explained yet. Most cases of viral endophthalmitis occur in weakened and severely ●

As previously mentioned, the most common kinds of endophthalmitis have an exogenous origin and are caused by pathogens that enter the eye through a wound or a corneal ulceration (surgical or traumatic). Traumatic endophthalmitis cases account for about 20% of the total and are caused by Bacillus, S epidermidis, and gramnegative bacteria. Fortunately, advances in surgical techniques and the improvement of prophylaxis and therapies have considerably reduced the incidence of postoperative endophthalmitis. The following are the main pathogens involved in postphacoemulsification endophthalmitis. Acute forms: BHS (β-hemolytic streptococci), Streptococcus mitis, S pneumoniae, Enterococcus faecalis ●

●

●

S aureus, coagulase-negative staphylococci (CNS) Gram-negative bacteria such as Haemophilus influenzae and P aeruginosa

Chronic forms: P acnes ●

●

Diphtheroids

●

CNS

Fungi At the beginning of the 21st century, the incidence of endophthalmitis after cataract surgery was 10%. In the ●

Prevention of Endophthalmitis  93 ECCE period, with incisions at the limbus or sclera, the incidence of endophthalmitis fell to 0.12% in Europe.25 Phaco retrospective studies have demonstrated a 0.015% incidence.26 There is a broad range of technical factors related to cataract surgery that can have a negative effect and increase the risk of endophthalmitis. Clear corneal incisions have led to a considerable reduction in endophthalmitis cases, and the cases associated with clear corneal incisions are related to the presence of wound dehiscence.27 Some pathological conditions can increase the risk of postoperative endophthalmitis (such as diabetes mellitus, pharmacological immune suppression, and conditions associated with altered bacterial flora). Acute endophthalmitis appears in a period of time between 1 day and 2 weeks after cataract surgery. Symptoms include pain in the eye, reduced vision, hypopyon, Tyndall effect, eyelid edema, and reddening. There can be corneal edema as well. The posterior segment may be involved, which causes loss of the red reflex. The late chronic forms can appear a few months after surgery. These forms are mainly caused by P acnes, S epidermidis, some diphtheroids, and fungi. The causative agent produces a fairly typical clinical picture; for example, infections caused by P acnes cause whitish plaques inside the capsular sac, whereas fungi infections are associated with hypopyon, corneal edema, and keratitis. The prognosis is always closely related to the number and virulence of the infectious agents present at the time of infection. The treatment of acute endophthalmitis must be started very quickly, no later than an hour from diagnosis. The gold standard of treatment is vitrectomy, which must be immediate and complete. After peribulbar or retrobulbar block, the vitreous and the infected material are removed. The infected material must be analyzed for the presence of pathogens after being extracted. Surgical posterior capsulotomy is performed to remove purulent material from the vitreous chamber. Surgical maneuvers must be performed with great caution because during endophthalmitis, there is often vasculitis with retinal edema, which can cause retinal detachment. Antibiotics and cortisone are injected at the end of vitrectomy. Should it not be possible to perform a vitrectomy procedure very soon after diagnosis, paracentesis of the anterior and posterior chamber can be carried out, with the intravitreal injection of antibiotics through a 25- or 30-gauge needle. Cortisone therapy is required as well because the massive inflammation of the posterior segment can cause the blood–retinal barrier to break. The intravitreal injection of an antibiotic mixture must be repeated at 48- to 72-hour intervals, depending on the clinical condition of the patient and taking into account the possibility of retinal toxicity. The most commonly used mixtures include vancomycin (1 mg) and ceftazidime (2 mg)28 (taking special care because vancomycin and ceftazidime29

mixed together in the same solution can cause the formation of precipitates) or amikacin (0.4 mg) and ceftazidime (2 mg). A 0.1-mL solution of each antibiotic of the selected combination must be injected separately after paracentesis or vitrectomy. An intravitreal injection of dexamethasone (0.4 g in 0.1 mL) is also necessary. The following tables list the intravitreal doses of the various antibiotics. Preparations: 5% to 10% povidone–iodine disinfecting solution: Prepare a 1:1 dilution of povidone–iodine solution with balanced salt solution (BSS) or isotonic saline solution. Remove about 1 mL with an insulin syringe and wash the conjunctival fornix and cornea. Ceftazidime for washing the anterior chamber (dose to use 2000 μg in the vitreous chamber): Dissolve 500 mg of the ceftazidime vial into 10 mL of 0.9% saline solution. Shake the vial well. Remove 2 mL of solution and add 3 mL of 0.9% saline solution. Draw 0.1 mL (= 2000 μg) and inject it into the vitreous. Vancomycin (dose to use 1000 μg): Dissolve 250 mg of the vancomycin vial into 10 mL of 0.9% saline solution. Shake the vial well. Remove 2 mL of solution and add 3 mL of 0.9% saline solution. Draw 0.1 mL (= 1000 μg). Amikacin (dose to use 400 μg): Dissolve 500 mg of the amikacin vial into 10 mL of 0.9% saline solution or BSS. Shake the vial well. Draw 0.8 mL using a 1-mL syringe and add 9.2 mL of 0.9% saline solution or BSS. Draw 0.1 mL (= 400 μg).

Gentamycin (dose to use 200 μg): Draw 0.5 mL using a 1-mL syringe from a vial containing 40 mg/mL gentamycin, add 9.5 mL of 0.9% saline solution or BSS, and use 0.1 mL (= 200 μg). Clindamycin (dose to use 1000 μg): Draw 2 mL from the vial containing 300 mg of clindamycin and add 1 mL of 0.9% saline solution or BSS; draw 1 mL with a 1-mL syringe, and add 9.5 mL of 0.9% saline solution or BSS. Use 0.1 mL (= 1000 μg).

Amphotericin (dose to use 5 μg): Dilute the 50-mg vial with 10 mL of water for injectable solutions. Draw 1 mL with a 1-mL syringe, add 9 mL of 5% dextrose solution, and complete the 1/100 dilution. Use 0.1 mL (= 5 μg). Miconazole (dose to use 10 μg): Use a 1-mL syringe to draw 1 mL from the 10 mg/mL miconazole vial for IV use and add 9 mL of 0.9% saline solution or BSS. Draw 0.1 mL (= 10 μg).

94  Chapter 15 The Endophthalmitis Vitrectomy Study, a multicenter study, has not shown that systemic antibiotic therapy has any positive effect on the clinical course of endophthalmitis.30 The antibiotics recommended for systemic therapy are the same used intravitreally (vancomycin and ceftazidime) in the case of particularly virulent acute bacterial endophthalmitis.31,32 In this case, the patient must be kept under close observation and admitted to the hospital. Vancomycin is effective against many gram-positive bacteria, and ceftazidime is used against gram-negative bacteria including P aeruginosa. Imipenem has good activity against gram-positive bacteria, and fluoroquinolones are quite effective against gram-negative bacteria, although they have not yet been tested intravitreally. This mixture can be considered if the administration of vancomycin and ceftazidime is contraindicated.33,34 Clindamycin, vancomycin, and ceftazidime have been proven to be effective in the case of endophthalmitis caused by P acnes,35 although the intravitreal injection must be combined with vitreal surgery.36,37 In the case of fungal infections, amphotericin can be used intravitreally and systemically but precautions are required because it is relatively toxic. Flucytosine can be used in association with Amphotericin B in the case of C albicans infections. Endophthalmitis attacks caused by Fusarium are particularly aggressive and resistant to therapy. Treatment includes surgical vitrectomy and intravitreal, intracameral, topical, and systemic pharmacological therapy. Fusarium is often not sensitive to amphotericin, so combined therapy with imidazoles is required.

EFFECTIVE ANTIBIOTIC TREATMENTS Pathogens

Effective antibiotic treatment

Gram positive

Vancomycin, Imipenem

Gram negative

Ceftazidime, Fluoroquinolones

P aeruginosa

Ceftazidime

P acnes

Clindamycin, Vancomycin, Ceftazidime

Fungi, C albicans

Amphotericin B, Flucytosine

Finally, it can be useful to start a systemic antiinflammatory therapy with corticosteroids in order to limit tissue destruction by activated leukocytes, to control the release of proinflammatory antigens following the destruction of bacterial cell walls, and to induce the release of intraocular cytokines. The intravitreal injection of dexamethasone (400 μg in 0.1 mL) at the end of vitrectomy causes the rapid reduction in the inflammatory reaction.38 The oral administration of prednisolone (1 or 2 mg/kg/day) from the day after the intravitreal injection of antibiotics—whether combined or not with vitrectomy—has not been shown to have any negative effect on the course of bacterial endophthalmitis, although it does reduce the inflammatory reaction.

In the case of chronic endophthalmitis, the causative pathogen must be identified. Some authors advise therapy with clarithromycin (250 mg twice a day for 2 weeks).23 Removing the IOL and performing vitrectomy (with the aspiration of purulent material) can be useful. If removing the IOL is postponed, a week’s intravitreal therapy with vancomycin and cefazolin or cefuroxime is required.

PROPHYLAXIS Prophylaxis begins in the operating room, which must have a specific ventilation system. To significantly reduce the environmental bacterial count, no less than 20 air changes per hour must occur for vertical and horizontal air flows. Surgical instruments must be appropriately sterilized in an autoclave or possibly be single use. Phacoemulsification cassettes must be single use and appropriately disposed of at the end of each round of surgery. BSS bottles must be used only for one patient and must be protected against all types of bacterial contamination. The disinfection of the operating field is important in the prevention of the risk of endophthalmitis. To begin with, the skin of the periorbital region must be disinfected with a 5% to 10% povidone–iodine solution,39 which must be left to act for at least 3 minutes. In the case of patients allergic to povidone–iodine, a 0.05% chlorhexidine aqueous solution can be used.40 The conjunctiva and cornea must be disinfected with a 5% povidone–iodine solution left to act for at least 3 minutes before being washed off with saline solution.41 Preoperative antibiotic therapy is required to reduce the bacterial count of the conjunctival sac. In the past, various combinations of antibiotics (such as quinolones, neomycin, bacitracin, and chloramphenicol) were used, but none clearly showed that they could reduce the risk of endophthalmitis.42 A retrospective study showed how ofloxacin is more effective at reducing the risk of endophthalmitis compared with ciprofloxacin.43 Antibiotics administered orally combined with topical antibiotic therapy starting 3 days before the scheduled date for surgery lead to a high concentration of antibiotics in the anterior chamber.44 Some in vitro studies have shown that ofloxacin and levofloxacin penetrated more effectively into the anterior chamber than povidone–iodine.45 Systemic IV antibiotic prophylaxis, the disinfection of the lacrimal duct, and cutting eyelashes before surgery have not been proven to significantly reduce the risk of endophthalmitis.46 Intraoperative antibiotic prophylaxis consists of injecting 1 mg of cefuroxime in 0.1 mL of saline solution into the anterior chamber at the end of the surgery. Diluting vancomycin and gentamycin in the BSS bottle has not been shown to actually reduce the risk of postoperative endophthalmitis.47 Experiments in vitro have shown that the

Prevention of Endophthalmitis  95 peak of vancomycin effectiveness is after 1 day, whereas the drug persists in the anterior chamber for only 3 hours. Finally, there is risk of dose-dependent retinal toxicity caused by aminoglycosides and the development of resistance to the drug.48 The postoperative use of antibiotics—especially in the case of clear corneal incisions—has shown a reduction in the risk of infection. The most recent studies suggest that topical quinolones (or chloramphenicol) should be instilled four times a day for 1 week after surgery.49 The recent ESCRS47 guidelines recommend the following therapy schedule for the antibiotic prophylaxis of postoperative endophthalmitis: Use of topical quinolone starting from 2 days before surgery

●

●

●

●

1.

2. 3.

●

●

●

●

●

Application of the same quinolone 1.5 hours before surgery

4.

Disinfection of the conjunctival fornix with a 5% povidone–iodine solution for at least 3 minutes before beginning surgery

5.

Disinfection of periorbital skin with a 10% povidone– iodine solution Application of the surgical drape moving eyelashes away from the operating field

6. 7. 8.

Execution of cataract surgery, preferably using a preloaded IOL Injection into the anterior chamber of 1 mg cefuroxime in 0.1 mL of saline solution

9. 10.

Instillation of a drop of topical quinolone at the end of surgery and other two times, at 5-minute intervals Instillation of a drop of topical quinolone 4 times a day for a week after surgery

11.

12.

PREPARATION OF ANTIBIOTICS AND STERILIZING SOLUTIONS

13.

Antibiotics and cleansing and disinfecting solutions must be prepared under sterile conditions using sterile materials. Some simple rules are crucially important such as the following: Never reinject diluted solutions back into the original drug vial because once opened the vials are not sterile anymore.

14.

Do not perform dilutions greater than 1:10 because they are ineffective.

18.

●

●

●

Do not reuse used syringes.

●

Do not reuse BSS bottles.

Inject the drug slowly into the vitreous (over 1 to 2 minutes).

REFERENCES

●

●

Handle drugs with the utmost care and safety, following dilution instructions exactly.

15. 16.

17.

19.

Bodnar Z, Clouser S, Mamalis N. Toxic anterior segment syndrome: update on the most common causes. J Cataract Refract Surg. 2012;38(11):1902-1910. Peyman G, Lee P, Seal DV. Endophthalmitis—diagnosis and management. London: Taylor & Francis; 2004:1-270. Sherwood DR, Rich WJ, Jacobs JS, Hart RJ, Fairchild YL. Bacterial contamination of intraocular and extraocular fluids during extracapsular cataract extraction. Eye. 1989;3:308-312. Dickey JB, Thompson KD, Jay WM. Anterior chamber aspirate cultures after uncomplicated cataract surgery. Am J Ophthalmol. 1991;112:278-282. Montan PG, Koranji G, Setterquist HE, Stridh A, Philipson BT, Wiklud K. Endophthalmitis after cataract surgery: Risk factors relating to technique and events of the operation and patient history. A retrospective case-control study. Opthalmology. 1998;105:2171-2177. Niederkorn JY. Immune privilege and immune regulation in the eye. Adv Immunol. 1990;48:191-226. Streilein JW. Ocular immune privilege and the Faustian dilemma. Invest Ophthalmol Vis Sci. 1996;37:1940-1950. Menikoff JA, Speaker MG, Marmor M, Raskin EM. A casecontrol study of risk factors for post-operative endophthalmitis. Ophthalmology. 1991;98:1761-1768. Kain HL. Prinzipien in der Behandlung der Endophthalmitis. Klin Monatsbl Augenheilkd. 1997;210:274-288. Engstrom RE Jr, Mondino BJ, Glasgow BJ, Pitchekian-Halabi H, Adamu SA. Immune response to Staphylococcus aureus endophthalmitis in a rabbit model. Invest Ophthalmol Vis Sci. 1991;32:663-667. Pleyer U, Mondino BJ, Adamu SA, Pitchekian-Halabi H, Engstrom RE Jr, Glasgow BJ. Immune response to Staphylococcus epidermidis endophthalmitis in a rabbit model. Invest Ophthalmol Vis Sci. 1992;33:2650-2663. Kon CH, Occleston NL, Aylward GW, Khaw PT. Expression of vitreous cytokines in proliferative vitreoretinopathy: a prospective study. Invest Ophthalmol Vis Sci. 1999;40:295-299. Cutler Peck CM, Brubaker J, Clouser S, Danford C, Edelhauser HE, Mamalis N. Toxic anterior segment syndrome: common causes. J Cataract Refract Surg. 2010;36(7):1073-1080. Cao X, Liu A, Zhang J, et al. Clinical analysis of endophthalmitis after phacoemulsification. Can J Ophthalmol. 2007;42(6):844-848. Dilly PN, Sellors PJ. Bacterial adhesion to intraocular lenses. J Cataract Refract Surg. 1999;15: 317-320. Ng EW, Barrett GD, Bowman R. In vitro bacterial adherence to hydrogel and poly(methyl methacrylate) intraocular lenses. J Cataract Refract Surg. 1996;22(Suppl 2):1331-1335. Arciola CR, Caramazza R, Pizzoferrato A. In vitro adhesion of Staphylococcus aureus on heparin-surface-modified intraocular lenses. J Cataract Refract Surg. 1994;20:158-161. Mayer E, Cadman D, Ewings P. A 10 year retrospective study of cataract surgery and endophthalmitis in a single eye unit: injectable lenses lower incidence of endophthalmitis. Br J Ophthalmol. 2003;87:867-869. Hawkins AS, Deutsch TA. Infectious endophthalmitis. Curr Infect Dis Rep. 1999;1(2):172-177.

96  Chapter 15 20. Han DP, Wisniewski SR, Wilson LA, et al. Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study. Am J Ophthalmol. 1996;122(1):1-17. 21. Kunimoto DY, Das T, Sharma S, et al. Microbiologic spectrum and susceptibility of isolates: part II. Posttraumatic endophthalmitis. Endophthalmitis Research Group. Am J Ophthalmol. 1999;128(2):242-244. 22. Buratto L, Lovisolo C, Moncalvi M, Iori M. Prevenzione e trattamento delle endoftalmiti. Collana di oftalmologia pratica. Fogliazza Ed.; 1994. 23. Kunimoto DY, Das T, Sharma S, et al. Microbiologic spectrum and susceptibility of isolates: part I. Postoperative endophthalmitis. Endophthalmitis Research Group. Am J Ophthalmol. 1999;128(2):240-242. 24. Results of the Endophthalmitis Vitrectomy Study. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Arch Ophthalmol. 1995;113(12):1479-1496. 25. Koc F, Sen E, Demirbay P, et al. Factors influencing treatment results in pseudophakic endophthalmitis. Eur J Ophthalmol. 2002;12:34-39. 26. Taban M, Behrens A, Newcomb RL, et al. Acute endophthalmitis following cataract surgery. Arch Ophthalmol. 2005;123:613-620. 27. Stonecipher KC, Parmley VC, Jensen H, Rousey JJ. Infectious endophthalmitis following sutureless cataract surgery. Arch Ophthalmol. 1991;109:1562-1563. 28. Kwok AK, Hui M, Pang CP, et al. An in vitro study of ceftazidime and vancomycin concentrations in various fluid media: implications for use in treating endophthalmitis. Invest Ophthalmol Vis Sci. 2002;43:1182-1188. 29. Fiscella RG. Physical incompatibility of vancomycin and ceftazidime for intravitreal injections. Arch Ophthalmol. 1992;110:16251629. 30. Endophthalmitis Vitrectomy Study Group: Results of the Endophthalmitis Vitrectomy Study Group. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of post-operative bacterial endophthalmitis. Arch Ophthalmol. 1995;113:1479-1496. 31. Durand ML. The Post-Endophthalmitis Vitrectomy Study Era. Arch Ophthalmol. 2002;120:233-234. 32. Sternberg P Jr, Martin DF. Management of endophthalmitis in the Post-Endophthalmitis Vitrectomy Study Era. Arch Ophthalmol. 2001;119:754-755. 33. Behrens-Baumann W, Martell J. Ciprofloxacin concentrations in human aqueous humor following intravenous administration. Chemotherapy. 1987;33:328-220. 34. Adenis JP, Mounier M, Salomon JL, Denis F. Human vitreous penetration of imipenem. Eur J Ophthalmol. 1994;4:115-117.

35. Abreu JA, Cordovés L. Chronic or saccular endophthalmitis: diagnosis and management. J Cataract Refract Surg. 2001;27:650-651. 36. Deramo VA, Ting TD. Treatment of Propionibacterium acnes endophthalmitis. Curr Opin Ophthalmol. 2001;12:225-229. 37. Aldave AJ, Stein JD, Deramo VA, Shah GK, Fischer DH, Maguire JI. Treatment strategies for post-operative Propionibacterium acnes endophthalmitis. Ophthalmology. 1999;106:2395-2401. 38. Das T, Jalali S, Gothwal VK, Sharma S, Naduvilath TJ. Intravitreal dexamethasone in exogenous bacterial endophthalmitis: results of a prospective randomized study. Br J Ophthalmol. 1999;83:1050-1055. 39. Shimada H, Arai S, Nakashizuka H, Hattori T, Yuzawa M. Reduction of anterior chamber contamination rate after cataract surgery by intraoperative surface irrigation with 0.25% povidoneiodine. Am J Ophthalmol. 2011;151(1):11-17. 40. Kramer A, Rudolph P. Efficacy and tolerance of selected antiseptic substances in respect of suitability for use on the eye. In: Kramer A, Behrens-Baumann W. eds. Antiseptic Prophylaxis and Therapy in Ocular Infections. S. Kargen AG, Basel; 2002:117-144. 41. Isenberg SJ, Apt L, Yoshimori R, Khwarg S. Chemical preparation of the eye in ophthalmic surgery. Comparison of povidoneiodine on the conjunctiva with a prophylactic antibiotic. Arch Ophthalmol. 1985;103:1340-1342. 42. Ciulla TA, Starr MB, Masket S. Bacterial endophthalmitis prophylaxis for cataract surgery. Ophthalmology. 2002;109:13-24. 43. Jensen MK, Fiscella RG, Crandall AS, et al. A retrospective study of endophthalmitis rates comparing quinolone antibiotics. Am J Ophthalmol. 2005;139:141-148. 44. Ta CN, Egbert PR, Singh K, Shriver EM, Blumenkranz MS, Mino de Kaspar H. Prospective randomized comparison of 3-day versus 1-hour preoperative ofloxacin prophylaxis for cataract surgery. Ophthalmology. 2002;109:2036-2040. 45. Keverline MR, Koealski RP, Dhaliwal DK. In vitro comparison of ciprofloxacin, ofloxacin, and povidone-iodine for surgical prophylaxis. J cataract Refract Surg. 2002;28:915-916. 46. Cordoves L, Abreu A, Seal D, Barry P. Intravitreal antibiotics: the emergency kit. J Cataract Refract Surg. 2001;27:971-972. 47. Barry P, Seal DV, Gettinby G, Lees F, Peterson M, Revie CW; ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: Preliminary report of principal results from a European multicenter study. J Cataract Refract Surg. 2006;32(3):407-10. Erratum in: J Cataract Refract Surg. 2006;32(5):709. 48. Gritz DC, Cevallos AV, Smolin G, Whitcher JP Jr. Antibiotic supplementation of intraocular irrigating solutions. An in vitro model of antibacterial action. Ophthalmology. 1996;103(8):12041208; discussion 1208-1209. 49. Walker S, Diaper CJ, Bowman R, Sweeney G, Seal DV, Kirkness CM. Lack of evidence for systemic toxicity following topical chloramphenicol use [Review]. Eye (Lond). 1998;12(Pt 5):875-879.

Part II

16 Ophthalmic Viscosurgical Devices for Modern Cataract Surgery Steve A. Arshinoff, MD, FRCSC Ophthalmic viscosurgical devices (OVDs; previously known as viscoelastics) are the primary tools used by ophthalmic surgeons to create the physical environments that can optimally enhance the facility of performance of the controlled, delicate intraocular maneuvers in modern anterior segment eye surgery of all types, most particularly cataract surgery. Since the introduction of Healon (Advanced Medical Optics) in 1979,1 OVDs have proliferated and become essential in anterior segment surgery for space creation, tissue stabilization, balancing pressure between the anterior and posterior segments of the eye, spatial partitioning to isolate specific areas from fluid turbulence, and protection of the corneal endothelial cells from surgical trauma, free radicals, and other surgical hazards.2 Understanding the unique physical characteristics of a given surgical environment that need to be controlled in surgery (especially when faced with a circumstance that alters the “usual” environment) and the different properties of the available OVDs, allows the surgeon to perform in a customized, more stable, and safer environment, and makes his or her surgery simpler and smoother in its execution. Before addressing the specific spatial problems encountered in surgery and how to deal with them, some understanding of the properties of the palette of OVDs available is important. The goal should always be to create an environment in which a given task can be performed easily, rather than learning to perform heroically in a difficult, unstable, and uncontrolled environment.

THE NATURE OF OPHTHALMIC VISCOSURGICAL DEVICES OVDs are pseudoplastic solutions of biopolymers. Only three biopolymers have been successfully used in OVDs. Sodium hyaluronate (hyaluronan, NaHa) is an extremely long chain polymer upon which the vast majority of OVDs depend for their properties. Chondroitin sulfate is a shorter chain, lower molecular weight biopolymer used as a “supplemental” additive to alter the properties of some hyaluronan-based OVDs. Hydroxypropyl methylcellulose (HPMC) is a much lower viscosity biopolymer used in the most economical OVDs. Pseudoplastic means that when we plot OVD viscosity versus the applied shear rate (a measure of the stress to which the viscoelastic is exposed in a standard rheometer), the viscosity of a pseudoplastic solution falls as the shear rate rises, but has a limiting value at very low shear rates (the “zero-shear viscosity”), thus always remaining fluid. If the viscosity continued to rise as shear rates fell, the OVD would eventually become solid, like “plastics” do, a behavior that is referred to as “plastic.” There are two other types of fluid rheologic behavior sometimes seen when performing rheologic measurements (Figure 16-1): Newtonian fluids possess constant viscosity independent of shear rate, whereas dilatant fluids, an example of which is egg whites, demonstrate increasing viscosity as shear rates increase (the opposite of pseudoplastics). OVDs useful in

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Buratto L, Brint SF, Sacchi L. Cataract Surgery: Introduction and Preparation (pp 99-107). © 2014 SLACK Incorporated.

100  Chapter 16

A

B

Figure 16-1. (A) Rheometric patterns of fluid viscosity in response to varying rates of shear. (B) Pseudoplasticity curves of common OVDs.

ophthalmic surgery must have low viscosity at high shear rates in order to permit injection through small bore cannulas and should have high enough viscosity at low shear rates to maintain surgical spaces, permitting delicate surgical maneuvers while maintaining anterior chamber depth. All OVDs that have been found to be useful, to date, possess pseudoplastic rheologic behavior. OVDs differ in their rheologically active polymeric substance(s), concentration(s), and chain length(s). These factors determine the viscosity, elasticity, and cohesion of the OVD, and also are the greatest determinants of other physical and chemical properties.3 The particular combination of constituents makes each commercial OVD unique, making generic reference to an OVD (eg, 1% NaHa) misleading about its properties, sometimes intentionally so, depending upon the source. Unlike the case with most drugs, generic OVDs are not equivalent, and use of proprietary names is strongly encouraged for OVDs to avoid confusion.

THE CLASSIFICATION OF OPHTHALMIC VISCOSURGICAL DEVICES Initially all cataract viscosurgery was done using the first OVD, Healon. When Viscoat (Alcon Laboratories) and HPMC appeared, a few years after Healon, surgeons divided themselves into two groups: one group that preferred to work with higher-viscosity cohesives (Healon and later others) and another group that preferred lower-viscosity dispersives (Viscoat or HPMCs). The staggering number of OVDs marketed since 1990 made their classification important in order for the surgeon to have a logical basis to understand the behavioral attributes of a given OVD in surgery, upon which to select one for a specific use and to design OVD usage methods. A functional classification of OVDs for ophthalmic surgery should be based on the physical properties that are most important in cataract surgery, not a system adopted from another field with different requirements (eg, the oil industry). After reviewing the various physical and chemical properties of OVDs, and assessing which were most pertinent to use in ophthalmic surgery, Arshinoff, in 1989, devised the first OVD classification scheme based on zero-shear viscosity, but noting the high correlation between zero-shear viscosity and relative degree of cohesion or dispersion (Table 16-1A).4,5 Higher-viscosity cohesives were excellent at creating spaces and sustaining pressure, whereas lower-viscosity dispersives were capable of partitioning spaces and coating tissues (Table 16-1B). Each group was poor at performing the tasks for which the other group excelled, and so surgeons were forced to choose an OVD based on which type of complication would most likely present in a particular case, and therefore desirable to avoid. The first change in this classification was the introduction of a higher zero-shear viscosity OVD, Healon GV (greater viscosity), in 1992, which gave rise to the new class of super viscous higher viscosity cohesive OVDs. The appearance of viscoadaptives, in 1998, required further expansion of the scheme (see Table 16-1A),6 and the more recent appearance of another new OVD, DisCoVisc (Alcon Laboratories), which does not fit into the previous classification because it is the result of an attempt to dissociate the historic correlation between zero-shear viscosity and cohesion in OVDs and create a viscous dispersive OVD, required a further, major modification of the scheme from a simple one-dimensional list to a two-dimensional table (Table 16-2).7

Ophthalmic Viscosurgical Devices for Modern Cataract Surgery  101

TABLE 16-1A.

THE CLASSIFICATION OF OPHTHALMIC VISCOSURGICAL DEVICES PRIOR TO 2005 (ARSHINOFF 1989-2000) Year of Class Appearance

OVD Class Range

1998

Viscoadaptives

1992

Higher-viscosity cohesives ●

●

1980 to 1987

Zero Shear Viscosity (mPa.s) 7-24 x

106

Approximation 10 Millions

Super viscous cohesives

1-5 x 106

Millions

Viscous cohesives

105

100 Thousands

‒

106

Lower-viscosity dispersives ●

●

Medium-viscosity dispersives

104 ‒ 105

10 Thousands

Very low viscosity dispersives

103

Thousands

‒

104

mPa.s = milliPascal seconds. Note that the primary parameter used for classification is zero-shear viscosity.

TABLE 16-1B.

OPTIMAL USES OF COHESIVE AND DISPERSIVE OPHTHALMIC VISCOSURGICAL DEVICES (VISCOADAPTIVES DESIGNED TO DO ALL) Higher-Viscosity Cohesives

Lower-Viscosity Dispersives

Create space

Prolonged retention

Induce and sustain pressure

Partition spaces

SOFT SHELL AND ULTIMATE SOFT SHELL TECHNIQUE A dilemma existed before the development of viscoadaptives. The surgeon needed to choose, before the intended procedure, between OVD groups, each of which was inadequate alone for all steps in a cataract procedure. This dilemma provided impetus to the development of the “viscoelastic dispersive–cohesive soft shell technique” (SST).8 Subsequently, when viscoadaptives were found to have their own different restrictions, the “ultimate soft shell technique” (USST) was devised to overcome those by pairing extremely viscous viscoadaptives with the ultimate low viscosity aqueous-based fluid, water, or balanced salt solution (BSS) (Figure 16-2).9 Both soft shell techniques recognize that more physical effects can be achieved with two fluids of disparate properties than can be achieved with any single fluid, and thus enable the enhancement of the behavior of any OVD, by using it in a logical combination with another, different, OVD. Attempts continue to be made to design a single OVD that can replace multiple OVD techniques (eg, DisCoVisc), but, despite the success these efforts have

achieved for routine cataract cases, a single OVD can never replace SST abilities to create rheologically different adjacent physical spaces that do not mix, thus providing a much better environment in which to deal with more complex cases. Consequently, OVD techniques designed to deal with complications are usually variations of the SST and USST. A few are presented next.

Managing Difficult Cases Fuchs Endothelial Dystrophy Fuchs’ endothelial dystrophy cases are best handled with a variation of SST. The idea is to first place a dispersive OVD on the lenticular surface and then pressurize it up against the corneal endothelium by injecting a cohesive OVD below it. During phaco, the cohesive OVD will likely be aspirated. At the end of the case, residual cohesive is removed, while the dispersive is left in the eye, as a thin layer coating the endothelium, to protect it. The eye is best treated with a cholinergic ocular hypotensive agent, either intracameral carbachol (for glaucoma patients—Miostat, Alcon Laboratories) or topical carbachol (I use 0.2% topically made in our pharmacy) to prevent postoperative intraocular pressure (IOP) spikes. If needed (patients with

102  Chapter 16

TABLE 16-2.

THE CLASSIFICATION OF OPHTHALMIC VISCOSURGICAL DEVICES 2013 V0 (Zero-shear viscosity) range Cohesive OVDs Cohesion-Dispersion Dispersive OVDs CDI < 30 ( % asp / (milliPascal.seconds, mPa.s) Index, CDI ≥ 30 ( % asp / mm Hg) mm Hg) 7 - 18 x 106 (ten millions)

I. Viscoadaptive Healon5 iVisc (MicroVisc) Phaco BD MultiVisc

1 - 5 x 106 (millions)

II. Higher-viscosity cohesives A. Super viscous cohesives Healon GV iVisc (MicroVisc, HyVisc) Plus BD Visc, AcriHylonPlus

105 - 106 (hundred thousands)

104 - 105 (ten thousands)

103 - 104 (thousands)

B. Viscous cohesives Healon iVisc (MicroVisc, HyVisc) EyefillHC Ophthalin Plus Provisc OpeganHi Biolon Prime Biolon Amvisc Plus Amvisc Ophthalin Eyefill SC

II. Higher-viscosity dispersives A. Super viscous dispersives none

B. Viscous dispersives DisCo Visc

III. Lower-viscosity cohesives A. Medium-viscosity cohesives none

III. Lower-viscosity dispersives A. Medium-viscosity dispersives Viscoat Biovisc Endogel Rayvisc Opelead Vitrax, Healon D, Healon Endocoat Cellugel Eyefill HD

B. Very low-viscosity cohesives none

B. Very low-viscosity dispersives Opegan OccuCoat Icell, Visilon, Ocuvis, Hymecel, Adatocel, Celoftal, ...*HPMCs

Modified from Arshinoff SA, JafariM. A new classification of ophthalmic viscosurgical devices (OVDs). J Cataract Refract Surg. 2005; 31: 2167-2171

Ophthalmic Viscosurgical Devices for Modern Cataract Surgery  103

Figure 16-2. Ultimate soft shell technique (USST).

pre-existing glaucoma) a topical prostaglandin analogue may also be added, but all agents that reduce aqueous production by the ciliary body delay OVD washout and are ineffective in reducing or preventing postoperative IOP spikes caused by OVDs.10

Zonular Deficiency It is not uncommon to encounter a posttraumatic situation or a patient with Marfan syndrome, high myopia, pseudoexfoliation, or another reason to be missing a significant portion of the zonular ring. SSTs have greatly simplified these cases. First, the area of zonular deficiency is covered with a dispersive OVD. Then a cohesive (SST) is injected behind the dispersive, centrally in the anterior chamber, to pressurize the anterior chamber (AC) and force most, if not all, of the bulging vitreous, along with some dispersive OVD around the cataractous lens. At the earliest sign of instability, a capsular tension ring, Cionni ring, or Ahmed segment is inserted and Grieshaber, or other, hooks may be used as needed. As there is no vitreous in the AC, these cases usually progress relatively routinely, with the capsular tension ring and OVDs in place.

Capsular Staining of White and Black Cataracts The first technique proposed for capsular staining was simply to fill the anterior chamber with Vision Blue, leave it in for 1 minute, and then wash it out and continue the surgery with OVD injection followed by capsulorrhexis.

Because of concern with the amount of dye used and its dispersion throughout the AC, in this technique, many have used trypan blue under an air bubble. Since I first began to use Vision Blue in late 1999, I have been using a variation of the USST.11 Marques et al12 published their 3-step technique, which differs from my USST technique in that the last two steps are reversed in order, but I prefer the USST method. Trypan blue is listed as a carcinogen in the Merck Index, and Yetil et al13 were able to successfully stain the anterior capsule with as little as 0.1 mL of 0.0125% trypan blue (one-fourth commercial concentration), and the general goal is to use as little dye as possible for capsular staining, in case it should later prove hazardous, as indocyanine green (ICG) did.14 Ultimate Soft Shell Capsular Dye Technique for Capsular Staining The ultimate soft shell capsular dye technique proceeds as follows: Fill the anterior chamber 80% to 90% with viscoadaptive OVD, being careful not to inject initially at the wound, which would blockade the incision hampering subsequent steps. ●

●

Paint trypan blue over the capsule, below the OVD, using only a tiny drop ejected onto the capsular surface through a 27-gauge hockey stick cannula, attached preferably to a tuberculin syringe containing trypan blue (Figure 16-3A). (Vision Blue is now supplied in its own syringe. This syringe is considerably more difficult to use than a tuberculin syringe, but after a bit of

104  Chapter 16 2. Viscoadaptive filled space (injected second) 1. Dispersive filled space (injected first)

A

3. BSS filled space (injected third) Incision : red – too short blk – good

Figure 16-4. The IFIS soft shell bridge (IFIS SSB).

the incision and pressurize the eye. Figure 16-3B illustrates the ensuing capsulorrhexis, showing the crystalclear view of the capsule that ensues.

B

Tamsulosin (Flomax; Astellas Pharma, Inc) Intraoperative Floppy Iris Syndrome (IFIS) The Intraoperative Floppy Iris Syndrome Soft Shell Bridge

Figure 16-3. The ultimate soft shell capsular dye technique (USSCDT). (A) After filling the anterior chamber 90% with a viscoadaptive, trypan blue is painted over the anterior capsule, beneath the OVD. (B) After washing excess trypan blue from the AC, and pressurizing the chamber with a brief burst of BSS, the USSCDT is seen to provide extreme clarity for capsulorrhexis in mature cataracts, while enabling pressurizing of the AC to prevent Argentinean Flag Syndrome.

practice, it works. Alternatively, the dye can be easily transferred to a tuberculin syringe.) The drop of trypan blue is then painted over the capsular surface using the distal “blade” of the hockey stick cannula. ●

Slowly inject BSS, xylocaine, or Xylo-Phe (Appendix) under the viscoadaptive onto the capsular surface, using a 27-gauge hockey stick cannula, washing out excess trypan blue. Then, suddenly increase the injection speed to a “pulse,” injected away from the wound, with the cannula aperture positioned remote from the incision, in the style of the USST. This will force the viscoadaptive upward and backward, toward the incision, to blockade

Intraoperative floppy iris syndrome is an ever more common problem due to the use of α-A1 antagonists, for benign prostatic hypertrophy, of which tamsulosin (Flomax) seems to be the worst, but it can occur with others and some psychiatric drugs as well. I have described an OVD technique to manage IFIS, which can be used alone, or in combination with iris hooks, or a Malyugin ring, depending on the severity of the case.15 Managing IFIS is best looked at as a series of maneuvers in a stepladder, progressing along the ladder in the more severe cases. The IFIS USB is performed as follows (Figure 16-4): Study the eye preoperatively: Determine if you are indeed dealing with IFIS or some other cause of small pupils (Is the iris atrophic? Is there a pupillary fibrotic ring? Are both pupils symmetrical? Is there a history of miotic use?). Perform a preoperative dilation test 1 to 2 weeks before surgery to confirm the presence and severity of expected IFIS as follows: Give tropicamide 1% gtt twice, 5 minutes apart, and phenylephrine 2.5% gtt once. After 20 minutes, the pupils are measured. ●

○

If the pupils exceed 6.5 mm, and especially if the patient has brown eyes, no particular difficulty is expected in surgery. Up to 0.5 mL of intracameral Xylo-Phe is injected through the side port, and after 30 seconds the main incision is made and the surgery is started. The IFIS soft shell bridge (SSB) is used, but the flow rate is not generally reduced below 25 mL/min.

Ophthalmic Viscosurgical Devices for Modern Cataract Surgery  105 ○

○

●

●

●

●

If the pupils are about 6 mm, some difficulty will be encountered and the IFIS SSB is used in addition to intracameral Xylo-Phe, with a flow rate of 20 mL/ min. If the pupils are less than 5.5 mm, and especially if the patient has blue irides, intracameral Xylo-Phe and IFIS SSB are used with flow rates in the range of 15 mL/min, and a Malyugin ring may be needed.

Tight incisions: Both the side-port and main phaco incisions are made tight and long. This prevents iris prolapse, and in the event of iris displacement, it goes under, rather than through the incision. IFIS SSB: The anterior chamber is then filled, through the phaco incision, with Viscoat (Alcon Laboratories), until the AC is about 40% full, making sure to inject it peripherally to cover the iris. Healon5 is then injected onto the surface of the anterior lens capsule, in the center of the AC, and proceeds, pushing the Viscoat upward and outward, until the pupil stops dilating. It is important that the boundary of the Healon5/Viscoat be near the pupillary margin. This will later serve as a fracture boundary, and will help to keep the iris stable, and the pupil dilated, throughout surgery. At this point, the AC should be about 90% full of OVD. Xylo-Phe is then injected slowly under the Healon5 layer, on the surface of the lens capsule, with the cannula aperture placed at the very center of the lens surface, to elevate the OVD soft shell, created above, off the lens surface, and create an aqueous pocket on the lenticular surface, confined to the lenticular surface, where the surgery will take place. Capsulorrhexis smaller than pupil: A routine capsulorrhexis is then performed using a bent needle, which will keep the AC OVD structure intact better than a forceps capsulorrhexis, beginning at the center of the lens, and being sure to keep the diameter of the capsulorrhexis slightly smaller than the pupil diameter. This will later act to confine fluid flow into an area smaller than the pupil, preventing turbulence from impacting the iris and the Viscoat layer, which would permit the pupil to flop and constrict. Careful hydrodissection: Hydrodissection is then performed with BSS on a 10-mL syringe with a Chang cannula, using small short pulses of BSS. As long as care is taken in performing the previous steps, as well as in placement of the BSS cannula, the BSS should be able to circulate around the lens and flow out of the eye, beneath the OVD shell, without disturbing the shell. If the OVD shell is disturbed in this step, and some OVD is lost, Healon5 is reinjected followed by BSS below it, before proceeding. The Viscoat placed peripherally is rarely washed out inadvertently, but the central Healon5 may be.

Figure 16-5. TriSoft shell technique (TSST).

Low flow, low chatter phaco: The Alcon Infiniti Phaco (or similar peristaltic) machine settings are adjusted to flow ≤ 20 mL/min, vacuum ≤ 300 mm Hg, bottle height 75 to 80 cm above patient’s eye, continuously variable pulse, or torsional mode. The procedure is performed using Phaco slice and separate or similar chopping technique, being sure to keep the phaco tip at or below the capsulorrhexis, and confining fluid flow into the capsular bag.16 All work is done in the capsular bag, and the phaco is only engaged when it is in the bag and in contact with a piece of nucleus. Unnecessary irrigation of the anterior chamber is avoided. When the previous steps are followed, paying careful attention to measuring the pupils preoperatively, creating tight incisions and a stable OVD environment, IFIS cases become relatively routine procedures. ●

TriSoft Shell Technique The TriSoft Shell Technique is a generalization of all previously described SSTs in order to conceptually simplify a system of rational OVD selection and use in combinations for different types of cases, as well as routine ones (Figure 16-5).18 Each of the preceding techniques combines multiple OVDs into distinct shells within the anterior chamber. Partitioning spaces in this way makes it possible to create vastly different adjacent physical environments within a single enclosed space, with rheological properties in each space chosen to best achieve an optimal environment in which to perform the desired surgical maneuvers. Routine combination of SST and USST concepts into a single general approach makes soft shell surgery more consistent and conceptually easier. The TriSoft Shell Technique (TSST) is performed as follows: After creating the side-port incision, the eye is anesthetized and pressurized, and the pupil dilated, using 0.1 mL of a lidocaine–phenylephrine mixture, XyloPhe, injected intracamerally. A 2.2-mm phaco incision (or other size based on the intended phaco machine) is then created. ●

106  Chapter 16 ●

●

●

●

●

The dispersive OVD (I prefer Viscoat; Alcon Laboratories: sodium hyaluronate 3%, chondroitin sulfate 4%) is injected through the phaco incision to form a central mound on the surface of the anterior capsule, stopping once the AC is about 20% to 25% full. A cohesive (eg, sodium hyaluronate 1% (Healon; AMO, Healon GV; AMO or Provisc; Alcon Laboratories) or preferably a viscoadaptive OVD (eg, Healon5; AMO, iVisc Phaco; I-Med Pharma), maximizing the rheological difference between the OVDs, is then injected beneath the dispersive onto the surface of the anterior capsule. This displaces the Viscoat shell upward against the endothelial surface of the cornea, creating a smooth, continuous dispersive shell to protect the endothelium. Injection of viscoadaptive should continue until the pupil stops dilating but before the eye becomes firm. At this point, a variant of the SST has been formed composed of a low-viscosity protective outer dispersive shell encircling either a cohesive or a viscoadaptive pressurizing and stabilizing inner shell. BSS, or lidocaine–phenylephrine (Xylo-Phe), is then injected slowly underneath the viscoadaptive layer, with the cannula aperture directed downward toward the lens surface. This creates a continuous lake of lowviscosity fluid directly on the lenticular surface, with the pupillary margin serving roughly as its minimal peripheral border. The viscoadaptive shell is displaced upward, creating a central bridge. Now, a variant of the USST has been created below the SST, hence the name “tri-soft shell.” In cases of white or brunescent cataract, trypan blue may also be added before the “Xylo-Phe step” to enhance visualization. A routine capsulorrhexis is performed using a bent needle or forceps. Because this takes place within the low-viscosity aqueous lake, minimal resistance is encountered when manipulating the instruments or capsular flap. Use of a bent needle will disturb the OVD shells less than a forceps. Hydrodissection is performed using BSS in a 10-mL syringe with a 27-gauge Chang cannula. Careful injection of BSS will allow it to circulate around the lens, underneath the OVD shells, and out of the eye through the phaco incision without disturbing the shells. Occasionally during hydrodissection, the shells may be disrupted and OVD will be lost. In this case, it is always the viscoadaptive layer that is lost. If this occurs, simply reinject the viscoadaptive layer and the BSS layer below it before proceeding. During the subsequent phaco procedure, the layered OVD shells are preserved better with lower flow rates. I routinely use a flow rate of 32 mL/min, a bottle height of 95 cm above the patient’s eye, and a vacuum limit of 330 mm Hg. In a patient with IFIS, or severe Fuchs’ endothelial dystrophy, the machine settings are

reduced to flow rate 15 to 25 mL/min, vacuum 200 to 250 mm Hg, and bottle height 75 to 80 cm. These cases take a bit longer, but the TSST shells remain completely undisturbed. In all cases, the phaco and irrigation/ aspiration (I/A) tips should be kept deep to the plane of the capsulorrhexis to contain flow within the capsular bag, minimizing the disturbance of the soft shells, and the turbulence to which the iris and the endothelium are exposed. Once the I/A has been completed, intraocular lens (IOL) insertion then proceeds as described for the USST previously. Briefly, viscoadaptive is injected into the AC beginning at the phaco incision to block the incision and partially (after experience is gained) or completely (initially) block the opening of the capsulorrhexis—but not into the capsular bag. Injection should continue until OVD just begins to enter the capsular bag. BSS injection is then performed into the capsular bag in a manner similar to that used during hydrodissection using a hockey stick cannula. The BSS injection pushes the OVD forward out of the capsular bag as it pushes the posterior capsule posteriorly. BSS injection ceases once the capsular bag is wide open. BSS is now sealed within the capsular bag by the viscoadaptive layer sealing the incision. The IOL is then inserted using a cartridge, with the low viscosity of the BSS shell encouraging the leading IOL haptic to open, while the trailing haptics remains folded within the OVD environment. The I/A is inserted into the eye and turned on as slight posterior nudging of the trailing haptics and IOL is exerted. The irrigation force, combined with the directional nudging of the IOL, causes the IOL to fall backward into the aqueous-filled capsular bag and open. The OVD shells are simultaneously removed using I/A. It all takes just a few seconds. Once the surgeon realizes that the IOL has fallen backward into the capsular bag, he or she also realizes that the OVD is completely gone from the eye. In cases where endothelial cell count (ECC) is a concern, the surgeon may elect to leave the dispersive layer in the eye, by keeping the I/A posteriorly in the AC, to avoid exposing the endothelium to the turbulence of I/A. Just to be doubly certain, postoperative IOP spikes can be prevented with one drop of carbachol 0.2% (cholinergic agents are the most effective to prevent postoperative IOP spikes, and carbachol lasts 24 hours). A low concentration is needed to prevent the patient from developing a headache.

SUMMARY OVDs are used almost universally in cataract surgery to create and preserve surgical spaces and protect endothelial cells. SST and USST techniques enable us to design variations that can assist us in almost any conceivable physical space and protection problem than may occur in cataract surgery. I have presented a few examples from which others can easily be derived. However, the multitude of situations

Ophthalmic Viscosurgical Devices for Modern Cataract Surgery  107 and corresponding SST can be confusing, so I have combined them into the TSST with broad applicability, and from which variations are fairly intuitively obvious. I have found that when the unexpected occurs, a good reaction is to sit back for a few seconds, think, and reach for whichever combination of OVD(s) can help best in the new situation. As our techniques continue to change in cataract surgery, we also must look for new approaches, but the principles remain the same. Femtosecond laser cataract surgery permits the initial capsulorrhexis, nuclear division, and incisions to be performed on closed eyes, but once the eye is open, endothelial protection from phaco may still be needed and individual circumstances, such as partial zonular absence, will require creation of soft shell structures before re-docking the laser with a soft dock to continue. TSST easily adapts to change.

APPENDIX: XYLOCAINEPHENYLEPHRINE MIXTURE FOR INTRACAMERAL USE: XYLO-PHE Richard Packard has previously published the use of intracameral phenylephrine, by diluting Bausch & Lomb (Chauvin) minims for floppy iris syndrome.17 Because Bausch & Lomb minims are stabilized with metabisulfite and also contain EDTA, I decided to maximally dilute it for intracameral use. Over the past few years, the following method has proved safe and extremely effective: 1. An entire minim (0.3 mL) of 10% phenylephrine (Bausch & Lomb) is added to 5 mL of BSS in a 6-mL syringe, achieving a final concentration of 0.57%. 2. The circulating nurse adds 2 to 3 drops of this solution to each polyamp (2 mL) of 1% nonpreserved xylocaine (Astra) on the scrub tray, yielding a concentration of 0.03% phenylephrine and 1% xylocaine for injection (300% dilution of the phenylephrine). 3. The surgeon injects 0.1 to 0.2 mL of this solution through the side port immediately after its creation, which is the first step in every cataract procedure. After the OVD has been placed into the AC, the surgeon injects another 0.1 to 0.2 mL of the same Xylo-Phe solution under the OVD, onto the lenticular surface in the USST or TSST fashion.

I have noticed outstanding pupillary dilation in all cases, including floppy iris patients, better than with anything else we have tried, making surgery much easier, even if IFIS patients. I have labeled this solution Xylo-Phe and used it now in more than 1000 cases with no noticeable negative effects. Xylocaine achieves complete paralysis of the pupillary sphincter, while phenylephrine is the most powerful stimulant of the iris dilator available.

REFERENCES 1. 2. 3. 4. 5.

6. 7.

8. 9. 10. 11. 12.

13.

14.

15.

16. 17. 18.

Balazs EA. Ultrapure hyaluronic acid and the use thereof. US Patent No. 4.141.973, 1973. October 17, 1979. Arshinoff SA. Dispersive and cohesive viscoelastic materials in phacoemulsification. Ophthalmic Pract. 1995;13:98-104. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg. 1999;25:167-173. Arshinoff SA. Comparative physical properties of ophthalmic viscoelastic materials. Ophthalmic Pract. 1989;7:16-36. Arshinoff S: Dispersive and cohesive viscoelastic materials in phacoemulsification. In: Solomon L, ed. Ophthalmic Advisory Panel at the ASCRS. April 9, 1994. Boston, MA: Medicopea International, Montreal; 1995:28-40. Arshinoff SA. Healon5 entering selected countries in Europe. Ocul Surg News. 1998;9:11-12. Arshinoff SA, Jafari M. A new classification of ophthalmic viscosurgical devices (OVDs)—2005. J Cataract Refract Surg. 2005;31:2167-2171. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J. Cataract Refract Surg. 1999;25(2):167-173. Arshinoff SA. Using BSS with viscoadaptives in the ultimate softshell technique. J Cataract Refract Surg. 2002;28(9):1509-1514. Arshinoff et al. FDA metaanalysis study of OVDs. Unpublished data on record. Arshinoff SA. Letter. Capsular dyes and the USST. J Cataract Refract Surg. 2005;31:259-260. Marques DM, Marques FF, Osher RH. Three-step technique for staining the anterior lens capsule with indocyanine green or trypan blue. J Cataract Refract Surg. 2004;30(1):13-16. Yetil H, Devranoglu K, Ozkan S. Determining the lowest trypan blue concentration that satisfactorily stains the anterior capsule. J Cataract Refract Surg. 2002;28(6):988-991. Gandorfer A, Haritoglou C, Gass CA, et al. Indocyanine greenassisted peeling of the internal limiting membrane may cause retinal damage. Am J Ophthalmol. 2001;132:431-433. Arshinoff SA. Modified SST–USST for tamsulosin-associated intraocular floppy-iris syndrome. J Cataract Refract Surg. 2006;32:559–561 (April); erratum, 1076. Arshinoff SA. Phaco slice and separate. J Cataract Refract Surg. 1999;25(4):474-478. Packard R. Phenylephrine for IFIS. Cataract Refract Surg Today. 2006; September:75-76. Arshinoff SA, Norman R. Tri-Soft shell technique. J Cataract Refract Surg. 2013;39:1196-1203.

17 Cataract Surgery Incisions Daniel Calladine, BMedSci, BMBS, FRCOphth Over the past few decades, with the introduction and widespread adoption of phacoemulsification techniques, cataract surgery has undergone a remarkable revolution. One of the most dramatic changes has been the type and size of cataract surgery incisions. Using older intra- and extracapsular techniques, incisions as large as 10 mm were often used, requiring multiple sutures to close. Nowadays, with modern “micro” incision phacoemulsification technology, main incisions with much narrower widths of around 2.0 mm are commonly used, which also have the ability to self-seal without sutures. This chapter will be mainly concerned with clear corneal incisions (CCIs), which are by far the most popular type of incision used in developed countries (Figure 17-1). It covers basic incision parameters, knife design, the intraoperative factors that affect incision architecture, and how to improve the self-sealing properties of these incisions together with a description of new “wound sealants.” There is also a section dedicated to the intraoperative complications that can occur because of incorrectly constructed incisions.

CLEAR CORNEAL INCISIONS CCIs are quick and easy to create, have a fast postoperative recovery, and should self-seal if constructed correctly. However, if constructed incorrectly, they can leak in the early postoperative period. A leaking wound can lead to hypotony and further gaping open of the incision, which may ultimately lead to ingress of tear film contaminants into the anterior chamber, thereby increasing the risk of endophthalmitis. During the widespread adoption of CCIs in the 1990s, there was an associated increase in the endophthalmitis rates reported in some countries. This

was theoretically linked to learning curve associated with CCIs, which are more likely to leak if created incorrectly.1 Nowadays, much more is known about how to construct CCIs correctly in a way to encourage them to self-seal. They are therefore much safer and, combined with their advantages, have grown rapidly in popularity. The key variables with regard to CCIs are incision width, length, and cross-sectional profile. Ideally the incision width should match the width of the instrument being used through it. This minimizes the unnecessary use of overly wide incisions and avoids leakage of fluid from the anterior chamber during the operation between the instrument and incision edges. By creating a tight seal, it helps to utilize the benefits of phacoemulsification machine fluid dynamics control. Different instruments are used through the main incisions and side-port incisions requiring the surgeon to think ahead and plan incision width correctly. For the main CCI, the width of the phacoemulsification needle and sleeve should dictate the incision width. To avoid needing to enlarge the incision, it is important to use a model of intraocular lens (IOL) that can be inserted without having to enlarge the incision (Table 17-1). Most knives for main incisions are classified by their width, which is typically the width at their widest point. Thus, if the whole blade enters the anterior chamber, then the width is the same as that stated by the blade width, whereas if the blade is stopped short of entering the anterior chamber, the width can only be guessed by eye or measured afterward. However, some blades have width marks that specify positions to stop the blade during incision construction. An example is the Bausch & Lomb blade for coaxial-micro incision techniques, which has width marks specifying 2.0 and 2.2 mm (Figure 17-2). This blade can therefore be used to stop mid-incision when the

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110  Chapter 17

Figure 17-1. A clear corneal main incision being constructed using a 2.2-mm wide Windsor Knife (Core Surgical). This knife has a single-bevel blade with a facet on its upward facing surface, the base of which can be used as an incision length measuring mark.

Figure 17-2. Bausch & Lomb 2.2-mm knife with width marks denoting 2.0 mm for the internal lip of the incision and a 2.2-mm-width mark, which is the width of the external lip of the incision.

TABLE 17-1.

A SELECTION OF COMMONLY USED PHACOEMULSIFICATION PLATFORMS SHOWING HOW INCISION WIDTH CAN BE MATCHED TO THE PHACO NEEDLE SLEEVE SIZE AND IOL INJECTION CARTRIDGE BEING USED Incision Width

Phaco Machine

Needle Sleeve

IOL Injection Cartridge

1.8 mm

Alcon Infiniti (Alcon Laboratories)

Microsmooth Nano (orange color)

D-cartridge using wound-assisted technique

Bausch & Lomb Stellaris (Bausch & Lomb)

C-MICS (blue/gray color) D-cartridge using wound-assisted technique

Alcon Infiniti

Microsmooth Ultra (pink C-cartridge using wound-assisted color) technique or D-cartridge

Bausch & Lomb Stellaris

C-MICS (blue/gray color) C-cartridge using wound-assisted technique or D-cartridge

AMO Sovereign (Abbott Medical Optics)

20 gauge (yellow color)

C-cartridge using wound-assisted technique or D-cartridge

Alcon Infiniti

Microsmooth Micro (purple color)

C-cartridge

Bausch & Lomb Stellaris

Standard (blue color)

C-cartridge

2.2 mm

2.75 mm

2.0-mm mark is in the endothelial layer, thereby creating a trapezoidal configuration incision. This type of incision is well suited to the coaxial micro incisional cataract surgery (C-MICS) blue/gray color sleeve that fits easily through the external 2.2-mm lip of the incision and then snugly within the internal 2.0-mm lip of the wound so as to reduce fluid leaking during surgery. In a similar way, IOL injectors of the appropriate size fit more easily in the external lip of a

trapezoidal incision, while maintaining a narrower internal lip if required for the phacoemulsification sleeve. For side-port incisions, the width is usually dictated by the gauge of irrigation and aspiration (I/A) handpieces being used. For example, when using 21-gauge bimanual I/A handpieces, two 21-gauge side-port incisions are required. The definition of gauge is based on an industrial standard for defining the diameter of metal wires, which was then

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Figure 17-3. High-resolution optical coherence tomography of a clear corneal incision. The yellow line is the course of the incision and represents the true “incision length,” the green line shows the chord length of the incision, and the angle of the incision is shown as the angle between tangents to the corneal curvature at the external edge of the incision relative to the chord length (angle A).

Figure 17-4. High-resolution optical coherence tomography of two separate main CCIs. The top image incision was constructed with a 2.2-mm-wide blade, to create a nearly square-shaped profile. The bottom image incision was constructed with a 1.8-mm-wide blade and is nearly a square-shaped incision.

Figure 17-5. A 2.75-mm-wide CCI that has been created too long, although this has an almost square configuration, reaches too far across the cornea, and will make visualization difficult by distorting the central corneal surface during phacoemulsification.

modified for use with hypodermic needles and narrow tubing used in medicine, where a smaller gauge number indicates a larger diameter. It is not a linear scale, which can make it difficult for the surgeon to calculate the incision width required for a given gauge of instrument. The incision width required for a particular gauge instrument can be estimated by the diameter of the gauge plus a small additional correction factor to allow the incision to open enough for the instrument. For example, the external diameter of 21 gauges is approximately 0.8 mm; with the addition of 0.1 to 0.2 mm correction factor at each side to allow the incision to stretch open, a 1.1- to 1.2-mm diameter incision should be suitable. Making the incision a little smaller than this will create a tighter seal around the instrument during use, but this can restrict maneuverability. Incision length typically refers to the traceable length along the course of the incision, whereas incision chord length refers to the length of a theoretical straight line drawn from the point of entry in the cornea to the point

of exit. It follows that a straight single-plane incision will have the same incision and chord length, whereas a curved incision will have a longer incision length than the chord length. The angle of incision is the angle between a tangent and the cornea curvature at which the incision begins relative to the chord of the incision. A larger angle therefore correlates with a steeper shorter incision (Figure 17-3). The correct incision length for phacoemulsification surgery will depend mainly on the width of the incision being used. To improve the self-sealing properties of incisions, it is helpful for them to have a square- or nearly squareshaped profile.2,3 A square profile is easier to achieve with a 1.8-mm-wide CCI, for example, where the length can also be 1.8-mm and with a 2.2-mm-wide CCI where the length can be 2.0 mm, making it nearly square (Figure 17-4). As the incision width increases beyond 2.2 mm, it becomes increasingly unpractical to have incisions with a square shape. Incisions that are too long make access into the anterior chamber awkward and can distort the corneal surface making visualization difficult (Figure 17-5). A compromise can be achieved when using incisions wider than 2.0 mm by making them as nearly square as possible by creating a multiple plane profile, which maximizes the incision length relative to the chord length of the incision. In order to help the surgeon achieve a known incision length, most manufacturers now include an incision length measuring mark on their upward facing surface of the blade of the knife. The distance of this mark from the cutting tip does vary between different manufacturers and also

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Figure 17-7. A high-resolution optical coherence tomography image of a three-plane CCI.

Figure 17-6. An Alcon 2.2-mm-wide single-bevel blade with an incision length-measuring mark.

Figure 17-8. An MVR blade being used to create a side-port incision from within an LRI. This same technique can be used to create main incisions normally by making a circumferential vertical incision one-third depth into the cornea, and then starting the main blade from within this.

between different widths of blades, so the surgeon needs to be vigilant and, in some cases, use them as an approximate guide only (Figure 17-6). It has already been explained how incision length, chord length, and angle can be used to describe the profile of an incision. However, it is also very important to consider the cross section of the incision. This can either be straight (single plane) or curved with either a discernible 2-plane or 3-plane profile (Figure 17-7), or a have a continuous curved profile as described by Dr. Howard Fine.4 By increasing the number of incision planes, the incision length increases relative to the chord length of the incision, which in theory will improve the structural integrity and self-sealing properties of the incision postoperatively. For incisions wider than 2 mm, this also helps to make the incision more square by increasing the incision length to nearer that of the width.

There are various ways of creating CCIs with multiple plane profiles. A two-step technique can be used where an initial steep corneal incision is made about one-third of the corneal thickness parallel to the limbus with either a 15- or 30-degree blade, or a diamond knife. The main incision is then started from the base of this incision where it is extended forward into the anterior chamber to create a tunnel of appropriate length before entering the anterior chamber. This type of incision is usually referred to as a Langerman hinge, and is particularly useful if the surgeon has also made an limbal relaxing incision (LRI) at the site of the incision so that the main incision can be started from inside the LRI (Figure 17-8). Care must be taken not to make the main incision too short and steep by accidentally starting the main incision from the base of the LRI, which would typically be to a depth of around 90% of corneal thickness. This is therefore avoided by starting the main incision in the superficial half of the LRI and making a tunnel within the stroma as described above. An alternative and very popular way of making CCIs multiplane is to use a three-plane technique in one step using a single type of blade. This is achieved by burying the tip of the blade steeply into the cornea at the limbus to an approximate depth of one-third of corneal thickness. The blade angle of incision is then flattened markedly by placing the underside of the blade on to the globe, and a tunnel of approximately 1.5 mm is made almost parallel to the corneal curvature within the stroma. The angle of insertion is then steepened again to enter the anterior chamber by directing the tip toward the center of the pupil to complete the incision (Figure 17-9). This technique is most easily achieved using a single-bevel blade. The placement of incisions varies markedly between surgeons depending on the techniques they are using. For vertical chopping, it is easier to have the side-port incision nearer to the main incision to create the necessary vertical cutting action with the chopper second instrument, without pushing the nucleus downward with the hilt of the instrument and breaking the occlusion with the phaco needle tip. When using four-quadrant nucelofractis and horizontal chopping techniques, this is less important and the sideport can be placed further away from the main incision if desired. Surgical comfort is of paramount importance, and

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Figure 17-9. A 3-plane incision construction technique using a 2.2-mm-wide Windsor Knife, which is a single-bevel blade with a facet on its upward surface that can also be used as an incision length measuring mark, and blade stability technology. Figure 17-10. The variations in bevel and facet design seen on modern-day ophthalmic blades.

therefore the location of main and side-port incisions must always reflect this. Some surgeons choose to operate on the steep meridian of corneal curvature, which means placing the main incision on this meridian and sometimes combining it with a limbal relaxing incision at 180 degrees to this. While this may be beneficial for larger incisions such as 2.75 mm where a small astigmatic effect may be created, for sub 2.2-mm “micro” incisions, this effect is negligible. Placement of the main incision superiorly is thought to better protect it by covering it with the upper eye lid. However, in contrast to this, by placing the incision temporally can improve access into the anterior chamber, especially in patients with a prominent front-orbital ridge. As the cornea is wider in the horizontal than in the vertical meridian, it is easier to make a longer incision in the temporal cornea, which should also improve its ability to self-seal. There has been a definite trend toward temporal incision surgery with the newer generation of cataract surgeons, and this is also probably due to the improvements in knife design, and the increasing confidence and reliability of this type of incision if constructed correctly. When using a bimanual I/A technique, the second side port should be placed between 150 and 180 degrees from the first side port. Care must be taken to construct side ports correctly, as these tend to be the incisions that leak as opposed to main incisions where often more care is taken during their creation. Ideally side ports should have a square profile where the incision length matches the incision width to improve their ability to self-seal. To improve maneuverability, they can be created with a trapezoid shape being wider at either the external or internal edge. The other edge, though, should be of the correct width for the gauge of the instrument being used to prevent excessive leakage.

KNIFE DESIGN The most common types of knife for creating CCIs are those with a steel blade. Manufacturers will typically produce a range of blade widths to suit different surgical techniques. For main incisions, it is important for the surgeon to choose the correct width to match their phacoemulsification sleeve and IOL insertion technique. In the preferred setup, an IOL is used that can be injected through a cartridge that fits into the main incision without having to enlarge it, either without assistance or by using a woundassisted technique. The blade of the knife usually has either a single- or double-plane bevel (Figure 17-10). A single-bevel blade is flat on its underside, which allows it to glide better and more easily create a multiplane profile by pivoting against a flat platform. A double-bevel blade is better suited in creating an incision with a single-plane profile. It is harder to pivot a double-bevel blade as the bevel on the underside does not provide a flat platform. Steel blade design continues to evolve at a rapid pace, with many different varieties to choose from. The surgeon must decide whether they want a “super sharp” tip versus one with a little more resistance. Some novel blade designs are now available, which have a bevel-on-a-bevel feature also known as a facet. These blades have a single bevel with a flat underside and a facet on the upward facing surface. The effect of the facet is to provide a gradual increase in cutting resistance as the blade passes through the cornea. This is important to counteract the natural decrease in cutting resistance as the tip of the blade begins to enter the anterior chamber, which can lead to jumping forward of the blade. Similar technology to support shaft of the blade and prevent unwanted flexing and

114  Chapter 17

Figure 17-12. Left images showing a blade with an obtuse cutting angle used with a three-plane construction technique and producing a mainly multiplane profile, and right images showing a blade with an acute angle giving rise to a mainly two-plane or single-plane profile.

Figure 17-11. The Windsor Knife has a handle that extends downward to support the neck of the blade, which helps prevent unwanted flexing.

Figure 17-13. Alcon 2.2-mm intrepid blade when used with a three-plane incision construction technique, as described in Figure 17-9, will produce a mainly three- and two-plane incision.

stored potential energy is also used, which aims to further improve the surgeon’s control over incision construction. The majority of blades in commercial use suffer from too much front end resistance, which then suddenly gives way as the blade enters the anterior chamber causing it to jump forward. Newer knives such as the Windsor Knife (Core Surgical) have a blade design that incorporates a facet to gradually increase cutting resistance and also blade stability technology to prevent flexing of the neck of the blade (Figure 17-11). By combining these two design features, unwanted jumping forward of the blade is prevented. Incision length measuring marks have become increasingly popular now that a consensus has developed on what defines a good CCI in terms of the correct incision length. Although these marks do vary between different manufacturers in terms of distance from the cutting tip and also with the width of the blade being used, they all represent an improvement from having no mark at all. If the surgeon finds that the mark is too near or too far from the tip, they can use it as an approximate reference but add in a small correction factor. For instance, if a single-bevel 2.2-mm-wide

blade is used to create an incision with a three-plane profile, the incision mark is used to define the point at which the second plane then becomes the third plane, but the overall chord length of the incision is too long. This can be rectified next time, as the surgeon can bury the tip of the blade deeper during the first plane before flattening the incision angle and completing the second plane as before to the measuring mark. This will have the effect of reducing the length of the third plane and therefore reducing the overall chord length of the incision. When using a three-plane incision construction technique as described in Figure 17-9, the angle of the tip of the blade has an effect on the proportion of the incision that is multiplane. For descriptive purposes, an obtuse tip will tend to produce an incision with two or three planes and, conversely, an acute tip will mainly produce an incision with two planes or a single plane (Figure 17-12). This effect occurs because the angle of incision has already started to change before the edges of the blade have cut into the cornea. By making a steel blade too obtuse, however, the front end cutting resistance is made too high for practical use. Most blades are therefore in the middle range with a tip angle of around 45 degrees. For these blades, it is easier to make a multiplane incision with a narrower blade of less than 2.2 mm. At this narrower width, the majority of the blade has already cut into the cornea before entering the anterior chamber. For wider incisions, it is often the case that the tip of the blade has already entered the anterior chamber before the edges of the blade begin cutting (see comparison of Figures 17-13 and 17-14). The yellow line in both these figures represents the ideal incision length as a measured distance from the tip of the blade; it can be seen on the wider blade how approximately half of the incision will not have been created until the blade has entered the anterior chamber. It therefore follows that for new micro (sub 2.2 mm) incisions with square or nearly square configurations, it is easier to create multiplane profile. Much enterprise has been given to developing knives for main incision construction. However, it tends to be side ports that have the maximum tendency to cause

Cataract Surgery Incisions  115

Figure 17-14. An Alcon 2.75-mm blade, which when used with a 3-plane incision construction technique as described in Figure 17-9, will tend to produce a mainly two-plane and single-plane incision profile. A potential consequence is that the single-plane profile at the edges can end up being shorter than desired (red line). Figure 17-15. The Windsor Knife side-port knife, which is based on the same design as the main incision blade: the width is calculated for a given gauge of instrument.

INTRAOPERATIVE FACTORS

Figure 17-16. The “fish mouthing” effect that occurs on the lateral sides of an incision during surgery. The effects tend to be more marked on one side than the other.

intraoperative problems or leak postoperatively. Some side-port knives are available that have been specifically designed for this purpose (Figure 17-15). These blades look similar to main incision blades apart from being considerably narrower and reference sized depending on the gauge of instruments intended to be used instead of by a defined width in millimeters. Side ports can, of course, be created using a variety of knives such as using the main incision blade, but only going in halfway; a 15-degree blade is useful for creating a side port with a trapezoidal shape, or a MVRtype blade, which aims to produce an incision to match a certain gauge. As with single-bevel main incision blades, single-bevel blades used to create side ports are better suited to creating a multiplane profile, whereas double-bevel blades, such as the MVR blade, are better for single-plane incisions. It follows that in order to use a knife effectively, the surgeon needs to be aware of the dimensions of its blade and the nature of its bevel, and these principles apply to ocular surgery in general.

The anatomy of CCIs at the end of surgery is usually quite different from how it was just after being created due to intraoperative factors that can affect the incision architecture. The most significant factor is stretching and damage from inserting and removing instruments, which can lead to gaping of the internal or external edges, loss of coaptation along the stromal tunnel, local detachment of Descemet’s membrane (DM), or abrasion of surrounding epithelium. Although quite striking in appearance when visualized in the immediate postoperative period using high-resolution optical coherence tomography, these changes often quickly resolve within a week of surgery.5 One of the most common locations in the incision that can be stretched is at the lateral edges where a “fish mouthing” effect is seen (Figure 17-16). Gripping or holding the incision with forceps at any point during surgery will tend to leave a visible depression or notch (Figure 17-17). More serious damage can occur from phacoemulsification burns when either excessive ultrasound energy is used or if the needle becomes clogged and heat energy builds up due to the loss of the cooling effects of aspiration. The appearance of the incision at the end of surgery is also affected by the intraocular pressure (IOP). With a low IOP, the incision would tend to gape internally, has loss of coaptation along the stromal tunnel, and is more likely to have local detachment of DM. In contrast, at high IOP, the incision often appears more closed and under tamponade. Stromal hydration using balanced salt solution (BSS) at the end of surgery is a useful technique for thickening up the surrounding cornea and maintaining a higher IOP

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Figure 17-18. An optical coherence tomography image showing the effect of stromal hydration with BSS on a 2.75-mm-wide CCI. The corneal thickness has been increased locally to 1.2 mm.

Figure 17-17. Top image shows a slit lamp photograph using cobalt blue light and fluorescein to show a corneal abrasion at the site where the main incision was gripped with forceps during IOL insertion. Bottom image is a grid capture optical coherence tomography encompassing the entire main incision for the same eye where the forceps mark can be clearly seen (white arrow).

(Figure 17-18).6 Obviously, care must be taken to not leave the IOP so high as to be dangerous, but an eye with an IOP on the upper end of normal is much more likely to be able to resist deforming forces from accidental trauma from removing the wire lid speculum or from squeezing of eyelids. An eye with a low or hypotonous IOP combined with gaping of the incision is potentially susceptible to ingress of tear film contaminants. By increasing the thickness of the surrounding cornea, stromal hydration also increases the incision length due to basic trigonometry.

SELF-SEALING PROPERTIES The advent of anterior segment optical coherence has greatly improved our understanding of CCI “wound architecture,” and in many instances highlights just how fragile these types of incisions can be (Figure 17-19).

The simple rule with regard to improving how well CCIs self-seal at the end of surgery is to remember incisions that are too short and too steep will leak. However, incisions that are overly long will make surgery difficult by distorting the corneal surface and causing awkward instrumentation. The compromise, as explained earlier, is to use a multiplaned incision profile so that the overall length of the incision is increased relative to the chord length. A multiplaned profile will also improve the inherent mechanical strength of the incision to resist deforming forces. By creating incisions with a square or nearly square shape and by considering previous information, the majority of incisions are likely to self-seal. However, it is always important to check for this at the end of surgery because even the best quality CCI is susceptible to intraoperative damage that can leave it vulnerable. There are two techniques recommended for checking if the incision has sealed. Both are best performed after reforming the anterior chamber with BSS at the end of surgery and usually before injecting intracameral or subconjunctival antibiotics. With the anterior chamber firm, a dry absorbent spear can gently touch and dry at the external lip of the incision and deform the limbus slightly. A leaking wound will be seen to form a bleb of fluid (Figure 17-20). If a leaking incision is seen, it can be hydrated with BSS to create local stromal edema, which can sometimes help it seal, but it is always important to recheck with an absorbent spear test afterward. Another useful way to check for wound leaking is to perform a Seidel test with a drop of fluorescein 2% on the eye. If the incision is still leaking, it is better to place a corneal suture. A leaking wound is a route for infection to enter the eye, which can lead to the devastating complication of endophthalmitis. Even if the wound seals eventually without an infection forming, there

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Figure 17-19. Two hours postoperative examination following routine uncomplicated cataract surgery. Left image shows a deep formed anterior chamber and a Seidel negative eye, but with a low IOP of 8 mm Hg. Right image of the same eye using optical coherence tomography clearly shows how the incision is gaping open internally and has significant loss of coaptation. Figure 17-20. A small bleb of fluid is seen to be leaking from the side-port incision despite stromal hydration with BSS. This incision required a corneal suture to seal effectively.

Figure 17-21. An optical coherence tomography image of a 2.75-mm-wide main incision in an eye seen 1 hour after routine cataract surgery, where it was noted to have a shallow anterior chamber and very low IOP (2 mm Hg). The incision was Seidel positive and was taken back to the operating room for suturing.

Figure 17-23. The hydrogel is mixed to activate the gelling process and then applied to the ocular surface as a liquid to cover the incisions.

Figure 17-22. The granny knot. Left image shows a single forehand throw. Middle shows a second single forehand throw completed and the knot tightened. Right image shows checking the incision is properly sealed using an absorbent sponge; the knot can then be locked by doing one single backhand throw followed by one single forehand throw.

by doing one backhand throw and a further forehand throw (Figure 17-22). This type of knot is generally very useful in many types of ocular surgery when using nylon or Prolene sutures; for example, when doing corneal graft surgery it helps avoid having to redo several of the initial graft sutures that tend to be tied off either too tight or too loose earlier in the procedure. The granny knot will hold reasonably well during surgery but must be tied off at the end of the procedure or it will loosen markedly in the postoperative period.

WOUND SEALANTS is also the increased risk of corneal epithelial ingrowth, which is invariably sight threatening. If, in the postoperative examination, the incision is leaking (Figure 17-21), it is advised to take the patient back to the operating room to place a suture. The most common suture material used is 10/0 nylon and the knot is usually left in situ for 2 to 3 months after surgery. A useful tying technique is to initially use a “granny” knot, with one completed throw and then a second forehand throw. This type of slip knot can be tightened to the desired tension while at the same time rechecking the incision has sealed using the absorbent spear test. With the anterior chamber then reformed and the incision closed under the correct tension, the knot can then be locked off

The development of wound sealants provides a useful device to help surgeons improve the sealing properties of CCIs. These are essentially in situ gel-forming hydrogels, which have the ability to be applied to the ocular surface as a liquid and set to form a gel in defined period of time, usually around 30 seconds (Figure 17-23). They should not be mistaken as glues, as they vary markedly from the cyanoacrylate glues typically used in medicine. They are also not formed of human tissue extracts such as fibrin-based adhesives. During the gelling process, the hydrogel adheres firmly to collagen-like–based tissue, such as the cornea and sclera, to form an adhered “hydrogel bandage.” The surface of the hydrogel becomes smooth and comfortable

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Figure 17-25. Slit lamp photograph by the author showing the ReSure PEG hydrogel applied over a cataract surgery clear corneal incision. Left: in white light the hydrogel is translucent; middle: following instillation of fluorescein dye and viewed in white light, the hydrogel absorbs the dye; right: in cobalt blue light the fluorescein fluoresces brightly clearly defining the extent of the hydrogel.

Figure 17-24. Photographs taken from the operating microscope during fornix-based trabeculectomy surgery where the ReSure hydrogel has been applied to the conjunctival–limbal incision. (A) The wound is dried with a cellulose sponge; (B) one drop of the hydrogel and accelerating component are placed on the foil packaging a few minutes before being required by the surgeon; (C) the surgeon uses the plastic end of the foam-tipped applicator to mix the two components; (D) the foam-tipped applicator is used to transfer the hydrogel to the ocular surface as seen in images E and F; (H) within 30 seconds, the hydrogel has formed a firm rubbery gel adhered to the ocular surface covering the wound; (I) a further transfer of hydrogel material has been applied to completely cover the wound.

for patients due to blinking movements of the eyelids that sheer off and smooth its surface. The degree and duration of adherence demonstrate a positive trend with the amount and depth of epithelial damage; in more severe cases of epithelial damage, it can remain in situ on the ocular surface for up to 2 weeks. Optical coherence tomography studies show how epithelial cells grow underneath the hydrogel and gradually displace it and do not grow over its surface.7 The ability of hydrogels to form a smooth protective bandage has also made them attractive to other types of ocular surgery, such as in trabeculectomy surgery, where they can be applied over the limbal–conjunctival wound (Figure 17-24). In order to achieve appropriate adhesion, the ocular surface at the site of application must be dry. If the hydrogel is applied to a wet surface, the hydrogel material will migrate with the fluid before it has time to polymerize over the wound. It is found that the best method for application is to place an absorbent spear over the wound using one hand, and then remove it just before applying the hydrogel with

the other hand. This coordinated hand movement ensures the wound is dry and allows proper adherence of the hydrogel to the incision. In the days following surgery, any colorant visualization aid will diffuse out of the hydrogel to leave behind a translucent material, which can make identifying the presence of the hydrogel difficult even when viewing it down the slit lamp microscope. To aid in visualization of the hydrogel, a drop of fluorescein is instilled into the eye, which is absorbed by the hydrophilic hydrogel making it fluoresce in cobalt blue light such that its presence can be clearly defined (Figure 17-25). Wound sealants should not be used as a substitute for correct incision construction techniques, but they do provide a useful adjunctive effect. They are particularly helpful if the external lip of the incision has been damaged during surgery, if the incision has accidentally been created too short and steep, or in patients undergoing toric IOL insertion where a stable anterior chamber is very important postoperatively to prevent unwanted rotation.

INTRAOPERATIVE COMPLICATIONS The two most common intraoperative complications are caused by creating incisions that are too short or steep and located too close to the limbus. A steep, short incision near the limbus can lead to troublesome iris prolapse (Figure 17-26). This is more likely to occur at the side-port incision because here the second instrument used during phacoemulsification is usually of a narrower gauge than the width of the instrument, whereas at the main incision the phaco sleeve tends to be well matched to the incision width. For patients undergoing topical anesthetic procedures, iris prolapse can be very painful. If severe, this can also lead to long-term iris damage, atrophy and glare, and intra- or postoperative hemorrhage and inflammation. When it occurs during the operation, there is an immediate tendency to

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Figure 17-27. The Packard “Fat Boy” chopper and manipulator (Duckworth and Kent) has a thickened shaft of a known gauge so that the side-port incision can be matched to it. This helps to prevent intraoperative leakage and therefore maximizes the benefits seen with modern-day phacodynamics.

Figure 17-26. A main incision that was created too short and steep immediately developed quite severe iris prolapse during hydrodissection and required suturing and creating a new main incision at a different location in order to complete the operation safely.

try and push it back directly through the offending incision with either an iris repositor or an ocular viscoelastic device (OVD). However, this is incorrect. If intracameral phenylephrine has not yet been used in the procedure, particularly if the iris is floppy, then now is a good time to inject this via a different incision while at the same time decompressing the anterior chamber. An OVD with dispersive properties can then also be used via a different incision to gently sweep and compress the iris downward away from the offending incision. Depending on the stage of the operation and severity of the iris prolapse, surgery can then be continued with some protection against a repeat event being provided by the dispersive characteristics of the OVD. Alternatively, it may be better to suture the offending incision closed and create a new correctly constructed incision nearby. Techniques have been designed to reduce the risk of iris prolapse from side-port incisions by using nucleus manipulators and choppers with thickened shafts such as the Packard “Fat Boy” (Duckworth and Kent) vertical

chopper (Figure 17-27). However, the simplest way to avoid iris prolapse is to create a good-quality incision in terms of location, width, length, and profile. If the incision is started too limbal, the external edge of the incision can catch the conjunctiva. During surgery, fluid leakage around the phaco sleeve then tracks underneath the conjunctiva leading to chemosis of the conjunctiva. In severe cases, this can lead to an arm band effect where a pool of fluid then comes to rest over the cornea, making visualization difficult. It can be corrected by performing a small conjunctival peritomy along the external lip of the incision and extending it outward a few millimeters on each lateral side of the incision.

REFERENCES 1.

2.

3.

4.

5.

6.

7.

Taban M, Behrens A, Newcomb RL, et al. Acute endophthalmitis following cataract surgery: a systematic review of the literature. Arch Ophthalmol. 2005;123(5):613-620. Ernest PH, Lavery KT, Kiessling LA. Relative strength of scleral corneal and clear corneal incisions constructed in cadaver eyes. J Cataract Refract Surg. 1994;20(6):626-629. Masket S, Belani S. Proper wound construction to prevent shortterm ocular hypotony after clear corneal incision cataract surgery. J Cataract Refract Surg. 2007;33(3):383-386. Fine IH, Hoffman RS, Packer M. Profile of clear corneal incisions demonstrates by optical coherence tomography. J Cataract Refract Surg. 2007;33(1):94-97. Calladine D, Packard R. Clear corneal incision architecture in the immediate postoperative period evaluated using optical coherence tomography. J Cataract Refract Surg. 2007;33(8):1429-1435. Calladine D, Tanner V. Optical coherence tomography of the effects of stromal hydration on clear corneal incision architecture. J Cataract Refract Surg. 2009;35(8):1367-1371. Calladine D, Ward M, Packard R. Adherent ocular bandage for clear corneal incisions in cataract surgery. J Cataract Refract Surg. 2010;36(11):1839-1848.

Recommended Reading Auffarth GU, Reddy KP, Ritter R, Holzer MP, Rabsilber TM. Comparison of the maximum applicable stretch force after femtosecond laser-assisted and manual anterior capsulotomy. J Cataract Refract Surg. 2013;39(1):105-109. Bodnar Z, Clouser S, Mamalis N. Toxic anterior segment syndrome: update on the most common causes. J Cataract Refract Surg. 2012;38(11):1902-1910. Buratto L, Bellucci R. Viscoelastici in chirurgia oftalmica. Vol. 2. Fabiano Editore. Buratto L, Giardini P. Viscoelastici in chirurgia oftalmica. Vol. 1. Fabiano Editore. Buratto L. Chirurgia della Cataratta Facoemulsificazione e stato dell’arte. Camo Srl Editore. Chee SP. Pseudo anterior capsule barrier for the management of posterior capsule rupture. J Cataract Refract Surg. 2012;38(8):1309-1315. Conrad-Hengerer I, Hengerer FH, Schultz T, Dick HB. Effect of femtosecond laser fragmentation on effective phacoemulsification time in cataract surgery. J Refract Surg. 2012;28(12):879-883. Fishkind WJ. The phaco machine: analysing new technology. Curr Opin Ophthalmol. 2013;24(1):41-46. Goldenberg D, Habot-Wilner Z, Glovinsky Y, Barequet IS. Endothelial cells and central corneal thickness after modified sutureless manual small-incision cataract surgery. Eur J Ophthalmol. 2013;23(5):658-663. Haridas A, Syrimi M, Al-Ahmar B, Hingorani M. Intraoperative floppy iris syndrome (IFIS) in patients receiving tamsulosin or doxazosin—a UK-based comparison of incidence and complication rates. Graefes Arch Clin Exp Ophthalmol. 2013;251(6):1541-1545.

Kerr NM, Abell RG, Vote BJ, Toh T. Intraocular pressure during femtosecond laser pretreatment of cataract. J Cataract Refract Surg. 2013;39(3):339-342. Kurian M, Das S, Umarani B, Nagappa S, Shetty R, Shetty BK. Y sign: clinical indicator to stop trenching and start cracking. J Cataract Refract Surg. 2013;39(4):493-496. Lauschke JL, Amjadi S, Lau OC, et al. Comparison of macular morphology between femtosecond laser-assisted and traditional cataract surgery. J Cataract Refract Surg. 2013;39(4):656-657. Lawless M, Bali SJ, Hodge C, Roberts TV, Chan C, Sutton G. Outcomes of femtosecond laser cataract surgery with a diffractive multifocal intraocular lens. J Refract Surg. 2012;28(12):859-864. Lorente R, de Rojas V, Vázquez de Parga P, et al. Intracameral phenylephrine 1.5% for prophylaxis against intraoperative floppy iris syndrome: prospective, randomized fellow eye study. Ophthalmology. 2012;119(10):2053-2058. Mahdy MA, Eid MZ, Mohammed MA, Hafez A, Bhatia J. Relationship between endothelial cell loss and microcoaxial phacoemulsification parameters in noncomplicated cataract surgery. Clin Ophthalmol. 2012;6:503-510. Malik KP, Goel R, Kamal S. Bimanual capsulorrhexis using Sinskey hook. Cont Lens Anterior Eye. 2012;35(5):228-229. Mencucci R, Giordano C, Favuzza E, Gicquel JJ, Spadea L, Menchini U. Astigmatism correction with toric intraocular lenses: wavefront aberrometry and quality of life. Br J Ophthalmol. 2013;97(5):578-582. Nagy ZZ, Filkorn T, Takács AI, et al. Anterior segment OCT imaging after femtosecond laser cataract surgery. J Refract Surg. 2013;29(2):110-112.

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122  Recommended Reading Nichamin LD. Endoilluminated infusion cannula for anterior segment surgery. J Cataract Refract Surg. 2012;38(8):1322-1324. Ostern AE, Sandvik GF, Drolsum L. Positioning of the posterior intraocular lens in the longer term following cataract surgery in eyes with and without pseudoexfoliation syndrome. Acta Ophthalmol. 2012. Palanker DV, Blumenkranz MS, Andersen D, et al. Femtosecond laser-assisted cataract surgery with integrated optical coherence tomography. Sci Transl Med. 2010;2(58):58ra85. Rückl T, Dexl AK, Bachernegg A, et al. Femtosecond laser-assisted intrastromal arcuate keratotomy to reduce corneal astigmatism. J Cataract Refract Surg. 2013;39(4):528-538. Sim BW, Amjadi S, Singh R, Bhardwaj G, Dubey R, Francis IC. Assessment of adequate removal of ophthalmic viscoelastic device with irrigation/aspiration by quantifying intraocular lens “judders”. Clin Experiment Ophthalmol. 2013;41(5):450-454.

Smith P, Tang L, Balntas V, et al. “Phaco Tracking”: an evolving paradigm in ophthalmic surgical training. JAMA Ophthalmol. 2013;21:1-3. Sorensen T, Chan CC, Bradley M, Braga-Mele R, Olson RJ. A comparison of cataract surgical practices in Canada and the United States. Can J Ophthalmol. 2012;47(2):131-139. Talamo JH, Gooding P, Angeley D, et al. Optical patient interface in femtosecond laser-assisted cataract surgery: contact corneal applanation versus liquid immersion. J Cataract Refract Surg. 2013;39(4):501-510. Trikha S, Turnbull AM, Morris RJ, Anderson DF, Hossain P. The journey to femtosecond laser-assisted cataract surgery: new beginnings or a false dawn? Eye (Lond). 2013;27(4):461-473. van den Berg TJ, Franssen L, Kruijt B, Coppens JE. History of ocular straylight measurement: A review. Z Med Phys. 2013;23(1):6-20.

FINANCIAL DISCLOSURES Dr. Steve A. Arshinoff is a consultant for Alcon Laboratories, Abbott Medical Optics, and Bausch & Lomb. Dr. Stephen Brint has no financial or proprietary interest in the materials presented herein. Dr. Lucio Buratto has not disclosed any relevant financial relationships. Dr. Daniel Calladine has not disclosed any relevant financial relationships. Dr. Laura Sacchi has no financial or proprietary interest in the materials presented herein.

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