Glaucoma Drainage Devices: A Practical Illustrated Guide [1st ed.] 978-981-13-5772-5;978-981-13-5773-2

Table of contents :
Front Matter ....Pages i-ix
The Glaucoma Treatment Paradigm: An Overview (Shibal Bhartiya, Parul Ichhpujani, Monica Gandhi)....Pages 1-6
Indications of Glaucoma Drainage Implant (Julie Pegu, Amit Purang, Monica Gandhi)....Pages 7-12
The Glaucoma Drainage Devices: Types and Models (Bhumika Sharma, Monica Gandhi, Usha Yadava)....Pages 13-17
Preparing the Patient for the Glaucoma Drainage Device Surgery (Parul Ichhpujani)....Pages 19-23
The Ideal Glaucoma Drainage Device: Which One to Choose? (Purvi Bhagat)....Pages 25-32
Surgical Technique of Implantation: AGV, Limbal Variant (Shibal Bhartiya, Monica Gandhi)....Pages 33-38
Pars Plana Ahmed Glaucoma Valve: Surgical Technique (Gowri J. Murthy, Praveen R. Murthy, Shaifali Chahar)....Pages 39-46
Surgical Technique for Baerveldt Glaucoma Devices (Gurjeet Jutley, Laura Crawley)....Pages 47-56
Molteno Implants: Surgical Technique (Parth R. Shah, Ashish Agar, Colin I. Clement)....Pages 57-66
AADI Technique (Suresh Kumar, Sahil Thakur)....Pages 67-72
Glaucoma Drainage Devices in Special Cases (Sirisha Senthil)....Pages 73-77
Combined Surgeries: Glaucoma Drainage Devices and Cataract (Sagarika Patyal, Santosh Kumar, Suneeta Dubey)....Pages 79-83
Glaucoma Drainage Devices (Ahmed Glaucoma Valve) in Penetrating Keratoplasty-Associated Glaucoma (Madhu Bhadauria)....Pages 85-91
Combined Surgeries: Glaucoma Drainage Devices with Boston KPro (Suneeta Dubey, Nidhi Gupta, Madhu Bhoot, Shalini Singh)....Pages 93-99
Glaucoma Drainage Devices in Children (Oscar Daniel Albis-Donado, Alejandra Hernandez-Oteyza)....Pages 101-107
Modifications of Surgical Techniques in Glaucoma Drainage Devices (Kleyton Barella, Vital Paulino Costa)....Pages 109-116
Glaucoma Drainage Devices: Complications and Their Management (Bhumika Sharma, Monica Gandhi, Suneeta Dubey, Usha Yadava)....Pages 117-125
Postoperative Care and Follow-Up of the Patient with Glaucoma Drainage Devices (Sushmita Kaushik, Gunjan Joshi)....Pages 127-133
Histological Considerations of Glaucoma Drainage Devices (Nadia Ríos-Acosta, Sonia Corredor-Casas)....Pages 135-141
Economic Considerations of Glaucoma Drainage Devices (Maneesh Singh, Arijit Mitra)....Pages 143-148
Quality of Life Following Glaucoma Drainage Device Surgery (Bernardo de Padua Soares Bezerra, Syril Dorairaj, Fabio Nishimura Kanadani)....Pages 149-154
Important Clinical Trials in Glaucoma Drainage Devices (Monica Gandhi, Anupma Lal, Shibal Bhartiya)....Pages 155-162
Newer Devices for Aqueous Drainage (Reena Choudhry, Isha Vatsal, Foram Desai)....Pages 163-173

Citation preview

Glaucoma Drainage Devices A Practical Illustrated Guide Monica Gandhi Shibal Bhartiya  Editors

123

Glaucoma Drainage Devices

Monica Gandhi  •  Shibal Bhartiya Editors

Glaucoma Drainage Devices A Practical Illustrated Guide

Editors Monica Gandhi Dr. Shroff’s Charity Eye Hospital New Delhi India

Shibal Bhartiya Fortis Memorial Research Institute Gurgaon India

ISBN 978-981-13-5772-5    ISBN 978-981-13-5773-2 (eBook) https://doi.org/10.1007/978-981-13-5773-2 © Springer Nature Singapore Pte Ltd. 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Glaucoma Drainage Devices: A Practical Illustrated Guide is the collaborative effort of some of the best clinician scientists and surgeons across the globe. We have tried our best to keep this book free of unnecessary text, concentrating more on what is relevant clinically, emphasizing on the surgical technique. You will find the book full of algorithms and flowcharts and lots of images for illustration of surgical steps. Each of the chapters is accompanied by videos that demonstrate the surgical techniques and tips and tricks that improve surgical outcomes. There are enough videos by some of the most skilled surgeons in the world, detailing modifications of surgical techniques which you can try in your surgical practice and choose one that suits you best. You will, therefore, find the Glaucoma Drainage Devices: A Practical Illustrated Guide to be a handy reference for when you are in the glaucoma clinic, deliberating what would be the best choice for your patient, surgically. You will find that the book and the accompanying videos are your best friends when you are learning how to implant a glaucoma drainage device or to refine your technique. So whether you are a glaucoma surgeon in training or a trained glaucoma practitioner, we are sure this book will prove to be invaluable in your operating room. We hope you enjoy reading the book to be a learning experience, editing it has definitely changed the way we look at glaucoma drainage devices in our clinical practice. With best wishes, New Delhi, India Gurgaon, India 

Monica Gandhi Shibal Bhartiya

v

Contents

1 The Glaucoma Treatment Paradigm: An Overview ��������������������   1 Shibal Bhartiya, Parul Ichhpujani, and Monica Gandhi 2 Indications of Glaucoma Drainage Implant����������������������������������   7 Julie Pegu, Amit Purang, and Monica Gandhi 3 The Glaucoma Drainage Devices: Types and Models������������������  13 Bhumika Sharma, Monica Gandhi, and Usha Yadava 4 Preparing the Patient for the Glaucoma Drainage Device Surgery���������������������������������������������������������������������������������  19 Parul Ichhpujani 5 The Ideal Glaucoma Drainage Device: Which One to Choose?��������������������������������������������������������������������  25 Purvi Bhagat 6 Surgical Technique of Implantation: AGV, Limbal Variant ��������������������������������������������������������������������������������  33 Shibal Bhartiya and Monica Gandhi 7 Pars Plana Ahmed Glaucoma Valve: Surgical Technique������������  39 Gowri J. Murthy, Praveen R. Murthy, and Shaifali Chahar 8 Surgical Technique for Baerveldt Glaucoma Devices������������������  47 Gurjeet Jutley and Laura Crawley 9 Molteno Implants: Surgical Technique������������������������������������������  57 Parth R. Shah, Ashish Agar, and Colin I. Clement 10 AADI Technique������������������������������������������������������������������������������  67 Suresh Kumar and Sahil Thakur 11 Glaucoma Drainage Devices in Special Cases ������������������������������  73 Sirisha Senthil 12 Combined Surgeries: Glaucoma Drainage Devices and Cataract ������������������������������������������������������������������������������������  79 Sagarika Patyal, Santosh Kumar, and Suneeta Dubey

vii

viii

13 Glaucoma Drainage Devices (Ahmed Glaucoma Valve) in Penetrating Keratoplasty-­Associated Glaucoma����������������������  85 Madhu Bhadauria 14 Combined Surgeries: Glaucoma Drainage Devices with Boston KPro ����������������������������������������������������������������������������  93 Suneeta Dubey, Nidhi Gupta, Madhu Bhoot, and Shalini Singh 15 Glaucoma Drainage Devices in Children�������������������������������������� 101 Oscar Daniel Albis-Donado and Alejandra Hernandez-Oteyza 16 Modifications of Surgical Techniques in Glaucoma Drainage Devices������������������������������������������������������������������������������ 109 Kleyton Barella and Vital Paulino Costa 17 Glaucoma Drainage Devices: Complications and Their Management ������������������������������������������������������������������ 117 Bhumika Sharma, Monica Gandhi, Suneeta Dubey, and Usha Yadava 18 Postoperative Care and Follow-Up of the Patient with Glaucoma Drainage Devices�������������������������������������������������� 127 Sushmita Kaushik and Gunjan Joshi 19 Histological Considerations of Glaucoma Drainage Devices������������������������������������������������������������������������������ 135 Nadia Ríos-Acosta and Sonia Corredor-Casas 20 Economic Considerations of Glaucoma Drainage Devices������������������������������������������������������������������������������ 143 Maneesh Singh and Arijit Mitra 21 Quality of Life Following Glaucoma Drainage Device Surgery���������������������������������������������������������������� 149 Bernardo de Padua Soares Bezerra, Syril Dorairaj, and Fabio Nishimura Kanadani 22 Important Clinical Trials in Glaucoma Drainage Devices������������������������������������������������������������������������������ 155 Monica Gandhi, Anupma Lal, and Shibal Bhartiya 23 Newer Devices for Aqueous Drainage�������������������������������������������� 163 Reena Choudhry, Isha Vatsal, and Foram Desai

Contents

About the Editors

Monica  Gandhi  is currently working as Associate Medical Director and Senior Consultant in Glaucoma and Anterior Segment Services at Dr. Shroff’s Charity Eye Hospital, New Delhi, India. She is an alumnus of Maulana Azad Medical College and Guru Nanak Eye Centre, under the University of Delhi. A former glaucoma fellow at the Glaucoma Imaging Centre under Prof. NN Sood, she has several publications and book chapters on glaucoma to her credit. Besides her keen interest in clinical and surgical training for fellows, she is also committed to mentoring fellows and trainees in their research work. Shibal Bhartiya  is currently working as a senior consultant glaucoma surgeon at Fortis Memorial Research Institute, Gurgaon, and Fortis Flt. Lt. Rajan Dhall Hospital, New Delhi, India. She has a special interest in glaucoma diagnosis and management and ocular surface diseases. She was a senior clinical research fellow in the glaucoma services of the Department of Clinical Neurosciences, University of Geneva, Switzerland. Prior to that, she did her glaucoma training as senior research associate in the cornea and glaucoma services at Dr. R P Centre for Ophthalmic Sciences, AIIMS, New Delhi. She has published extensively on glaucoma, contributing numerous articles and book chapters alike. She has coedited the prestigious ISGS Textbook of Glaucoma Surgery, Manual of Glaucoma, and Practical Perimetry; has coauthored Living with Glaucoma; and is the managing editor of the Video Atlas of Glaucoma Surgery. An avid educator and researcher, she has been responsible for the design and execution of many clinical trials involving both clinical and basic research. She serves as a reviewer for many ophthalmology journals and is the executive editor of the Journal of Current Glaucoma Practice, the official journal of the International Society of Glaucoma Surgery. She is also the editor in chief of Clinical and Experimental Vision and Eye Research.

ix

1

The Glaucoma Treatment Paradigm: An Overview Shibal Bhartiya, Parul Ichhpujani, and Monica Gandhi

1.1

Introduction

The only evidence-based, accepted, and the most practiced therapeutic modality for management of glaucoma patients is reducing intraocular pressure. Topical ocular hypotensive medications, as well as laser and incisional glaucoma filtering surgeries, all aim to decrease the IOP, thereby preventing visual field damage by decreasing the rate of retinal ganglion cells death. This chapter aims to provide an objective overview of current glaucoma practice in order to help decision-making for clinicians.

is unlikely to affect the patient’s quality of life. Risk stratification helps to guide target IOP (Table 1.1). The burdens and risks of therapy should be balanced against the risk of disease progression [1]. Therefore, important determinants when prescribing include choosing drugs with maximal efficacy, compliance, safety, persistence, and affordability (Table 1.2). Regular follow-up is necessary to detect progression and reassess target IOP, which might require escalation or downregulation of therapy. The follow-up duration depends on the stage of the disease, stability, and access to healthcare [2].

1.2

1.2.2 How to Augment Therapy

Medical Management of Glaucoma

1.2.1 How to Initiate Therapy The primary aim of medical treatment is to obtain the target IOP, which is defined as the IOP range at which the clinician judges that progressive disease S. Bhartiya (*) Department of Ophthalmology, Fortis Memorial Research Institute, Gurgaon, India P. Ichhpujani (*) Department of Ophthalmology, Government Medical College and Hospital, Chandigarh, India M. Gandhi (*) Department of Ophthalmology, Dr Shroff’s Charity Eye Hospital, New Delhi, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_1

In case, monotherapy is unable to meet the target IOP, and the first drug has been proven to be efficacious, a second drug may be added to the treatment protocol. Advantages of fixed combination preparations include ease of use, improved patient adherence, less preservative toxicity, and better tolerability. Maximal Medical Therapy (MMT): Maximal medical therapy can be defined as the minimum number and concentration of drugs (within the combination of different classes of medications) that provides maximum lowering of IOP.  It has to take into account factors including efficacy, compliance, tolerability, and affordability of ­glaucoma treatment, customized to the needs of the individual patient. 1

S. Bhartiya et al.

2

Table 1.1  Risk categories to guide treatment targets for POAG (Adapted from Asia-Pacific Glaucoma Guidelines, 2nd edition, 2008) Risk category Description High Moderate to advanced GON with VFD Higher IOP Rapid progression Bilateral visual field defects Pigmentary or pseudoexfoliative glaucoma Split fixation Glaucoma-related visual disability Younger age Moderate Mild GON with early VFD Mild-moderate GON with low IOP Younger age Fellow eye of established GON: (excluding secondary unilateral Glaucoma suspect with glaucoma) OHTN with multiple risk factors: thin CCT, high IOP, suspicious discs moderate GLC gene mutations associated with severe POAG risk Recurrent disc hemorrhages Pseudoexfoliation Younger age Glaucoma suspect with low risk

OHTN Older age Pigment dispersion with normal IOP Disc suspect Positive family history of glaucoma Less important:  Steroid responder  Myopia   β-peripapillary atrophy  Diabetes mellitus  Uveitis  Systemic hypertension

Treatment targets ≥40% IOP reduction or 1–2 SD below population mean (9–12 mmHg)

>30% IOP reduction or population mean Monitor closely for change or treat depending on risk and patient preferences Treat if risk(s) increase(s) with ≥20% IOP reduction or 1 SD above population mean Monitor

GON glaucomatous optic neuropathy, VFD visual field defects, IOP intraocular pressure, OHTN ocular hypertension, SD standard deviation Table 1.2  Broad classification of common ocular hypotensive agents IOP-lowering agent class Prostaglandin analogues

β-blockers

α2-agonists Carbonic anhydrase inhibitors

Cholinergics

Important drugs Latanoprost Travoprost Bimatoprost Tafluprost Timolol (0.25 or 0.5%) Betaxolol (0.25 or 0.5%)

Dosage A day, at bedtime

Brimonidine (0.15 or 0.2%), apraclonidine Brinzolamide Dorzolamide

Twice a day Twice or thrice a day

Pilocarpine (1, 2 or 4%)

Two to four times a day

Once or twice a day

Side effects Red eyes, dry eyes Iris pigmentation Eyelid skin darkening Longer, thicker lashes Bradycardia Bronchospasm Syncope, impotence Lipid disturbances Allergy Allergy, tachyphylaxis Hypotension Blurred vision Stinging, of dry eye Sulfonamides: Stevens-­Johnson syndrome, blood dyscrasias Allergy Headache, cataract, epiphora, change in vision, increased salivation, abdominal cramps

Contraindications Trimester 3 pregnancy (uterine contractility) Herpes infections of the eye Uveitis Heart block Asthma/COPD Caution in heart failure Betaxolol is cardioselective and has fewer pulmonary complications Avoid brimonidine in children 270° of the eye, it will not be possible to implant a GDI as fixing the plate to the underlying thin sclera may cause perforation. In phakic patients with shallow anterior chamber, GDI should not be implanted due to the risk of corneal touch. In patients who have a flat anterior chamber with no posterior view, or in eyes with total adherent leucoma, GDIs cannot be implanted unless combined with a cornea rescue procedure.

2.4

Summary

Surgeons typically keep GDI as the last reserve for control of IOP, but the GDI has gained more popularity with a shift in practice patterns over time as an initial treatment because of dreaded complications associated with trabeculectomy. The final choice of surgery depends on surgeon preference, but when managing high-risk ­glaucoma patients, patients likely to need future surgery or patient where the follow up is questionable, a tube implant procedure is preferred.

References 1. Kwon YH, Taylor JM, Hong S, et  al. Long-term results of eyes with penetrating keratoplasty and glaucoma drainage tube implant. Ophthalmology. 2001;108:272–8. 2. Arroyave CP, Scott IU, Fantes FE, et al. Corneal graft survival and intraocular pressure control after pen-

12 etrating keratoplasty and glaucoma drainage device implantation. Ophthalmology. 2001;108:1978–85. 3. Sidoti PA, Mosny AY, Ritterband DC, et  al. Pars plana tube insertion of glaucoma drainage implants and penetrating keratoplasty in patients with coexisting glaucoma and corneal disease. Ophthalmology. 2001;108:1050–8. 4. Burgoyne JK, WuDunn D, Lakhani V, et al. Outcomes of sequential tube shunts in complicated glaucoma. Ophthalmology. 2000;107:309–14. 5. Netland PA, Terada H, Dohlman CH.  Glaucoma associated with keratoprosthesis. Ophthalmology. 1998;105(4):751–7. 6. Freedman SF, McCormick K, Cox TA.  Mitomycin C augmented trabeculectomy with post-operative wound modulation in pediatric glaucoma. J AAPOS. 1999;3:117–24. 7. Blanco R, Wilson R, Spaeth G, et al. Filtration procedures supplemented with mitomycin C in the management of childhood glaucoma. B J Ophthalmol. 1999;83:151–6. 8. Pakravan M, Homayoon N, Shahin Y, et  al. Trabeculectomy with mitomycin C versus Ahmed glaucoma implant with mitomycin C for treatment of pediatric aphakic glaucoma. J Glaucoma. 2007;16:631–6. 9. Beck AD, Freedman S, Kammer J, et  al. Aqueous shunt devices compared with trabeculectomy with

J. Pegu et al. mitimycin C for children in the first two years of life. J Ophthalmol. 2003;136:994–1000. 10. Kim DK, Aslanides IM, Schmidt CM Jr, et  al. Long-term outcome of aqueous shunt surgery in ten patients with iridocorneal endothelial syndrome. Ophthalmology. 1999;106:1030–4. 11. Ishida K, Ahmed II, Netland PA.  Ahmed glau coma valve surgical outcomes in eyes with and without silicone oil endotamponade. J Glaucoma. 2009;18(4):325–30. 12. Sidoti PA, Belmonte SJ, Liebmann JM, Ritch R.  Trabeculectomy with mitomycin-C in the treatment of pediatric glaucomas. Ophthalmology. 2000;107(3):422–9. 13. Beck AD, Freedman S, Kammer J, et  al. Aqueous shunt devices compared with trabeculectomy with mitomycin-C for children in the first two years of life. Am J Ophthalmol. 2003;136:994–1000. 14. Hill R, Ohanesian R, Voskanyan L, et  al. The Armenian Eye Care Project: surgical outcomes of complicated pediatric glaucoma. Br J Ophthalmol. 2003;87:673–6. 15. Iwach AG, Hoskins HD Jr, Hetherington J Jr, Shaffer RN.  Analysis of surgical and medical management of glaucoma on Sturge-Weber syndrome. Ophthalmology. 1990;97:904–9.

3

The Glaucoma Drainage Devices: Types and Models Bhumika Sharma, Monica Gandhi, and Usha Yadava

3.1

Introduction

Glaucoma drainage devices are designed to divert aqueous humor from the anterior chamber to the subconjunctival space. In 1912 the first attempt was made by Zorab [1] with a silk thread for translimbal aqueous drainage, and subsequently attempts were made with gold [2], platinum [3], and tantalum [4], but the results were poor because of uncontrolled flow, hypotony, and foreign body inflammatory reaction. Molteno in 1969 introduced the concept of a device that consisted of a long acrylic tube attached to an acrylic plate sutured to the sclera adjacent to the limbus, but this had a high failure rate due to bleb perforation or end plate exposure [5]. In 1973 Molteno introduced the concept of draining the aqueous away from the limbus [6], placing the end plate at the equatorial region, and all of the currently available glaucoma drainage devices are based on this concept.

B. Sharma (*) · U. Yadava Guru Nanak Eye Centre, Maulana Azad Medical College, New Delhi, India M. Gandhi Anterior Segment and Glaucoma Services, Department of Ophthalmology, Dr. Shroff’s Charity Eye Hospital, New Delhi, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_3

3.2

Classification

The conventional glaucoma drainage devices consist of a tube that shunts the aqueous to an end plate located at the equatorial region. These devices can be further divided into valved or non-­ valved implants, depending on whether a valve mechanism is present to restrict the outflow when the IOP becomes too low.

3.2.1 A  hmed Glaucoma Valve (AGV) (Fig. 3.1) AGV is a silicone tube connected to a silicone sheet valve held in a scarab-shaped end plate of polypropylene (model S2, S3, B1) or silicone (model FP8, FP7, FX1). The valve consists of a thin silicon elastomer membrane to reduce internal friction within the valve system. The AGV consists of a tapered trapezoidal chamber. A Venturi effect is generated to help aqueous flow through the device. The velocity of aqueous entering the larger port of the Venturi chamber increases significantly as it exits the smaller outlet port of the tapered chamber. The increased exit velocity helps in evacuating the aqueous from the valve, in effect reducing the valve friction. The valve is designed to restrict the outflow when intraocular pressure is less than 8  mmHg [7–10]. End plate size of AGV is available from 96 mm2 (S3, FP8) to 364 mm2 (B1, FX1). 13

B. Sharma et al.

14 Model FP7 Ahmed® Glaucoma Valve - Flexible Plate

16.0 mm

Plate/Valve Thickness: 2.1 mm

Tube Outer Diameter 0.635 mm

Tube Inner Diameter 0.305 mm

13.0 mm Tube Length: 25.4 mm

Surface Area: 184.0 mm2

Fig. 3.1  Ahmed glaucoma valve FP7 Table 3.1  Specifications of the commonly used AGV models Ahmed glaucoma valve models FP7 Plate material Medical grade silicone Plate thickness 2.1 mm Plate surface 184.0 mm2 area Tube material Medical grade silicone Tube length 25.4 mm Tube inner 0.305 mm diameter Tube outer 0.635 mm diameter Valve material Medical grade silicone, elastomer membrane Valve casing Medical grade polypropylene

FP8 (pediatric) Medical grade silicone 2.1 mm 102.0 mm2

S2 Medical grade polypropylene 1.6 mm 184.0 mm2

S3 (pediatric) Medical grade polypropylene 1.6 mm 85.0 mm2

Medical grade silicone 25.4 mm 0.305 mm

Medical grade silicone 25.4 mm 0.305 mm

Medical grade silicone 25.4 mm 0.305 mm

0.635 mm

0.635 mm

0.635 mm

Medical grade silicone, elastomer membrane Medical grade polypropylene

Medical grade silicone, elastomer membrane Medical grade polypropylene

Medical grade silicone, elastomer membrane Medical grade polypropylene

A new model M4 [11] was introduced with a modification of a porous polyethylene shell. It was anticipated to reduce encapsulation and provide better tissue integration, thereby a better IOP control. Initial studies noticed an effective reduction of IOP in the early postoperative stage, but the failure rates after 1 year were reported to be high.

The rate of hypertensive phase was noted to be less as compared to other AGV models. Further studies and evaluation of the model showed that the outcome and failure rates were not acceptable hence the production of the model was discontinued [12] (Tables 3.1 and 3.2).

3  The Glaucoma Drainage Devices: Types and Models

3.2.1.1 Tube Extenders for AGV In certain cases, the tube may fall short and is needed to be extended. Model TE tube extender is available which can be used to extend the existing tube. It has a flange which is sutured to the sclera.

15

3.2.3 Molteno Implant (Fig. 3.2)

Krupin slit valve consists of a silicone tube with a unidirectional horizontal and vertical slit valve at its distal end, attached to a silicone oval disc with a surface area of 183 mm2. Alternatively, the tube may be attached to a #220 silastic band. The opening pressure of the slit valve is designed to be 10–12  mmHg, and the closing pressure is designed to be 8–10 mmHg [13].

Single-plate Molteno implant is a silicone tube attached to 134 mm2 polypropylene end plate. In 1981 Molteno introduced the double-plate Molteno (DPM) with a surface area of 274 mm2 with the second end plate attached to the right or left of the original end plate [14]. The two plates in double-plate Molteno implant are connected by a 10-mm-long silicone tube. Molteno dual ridge device contains V-shaped ridge on the surface of end plate. Pressure ridge reduces the risk of postoperative hypotony by restricting initial aqueous drainage to the small primary drainage area until the IOP rises sufficiently to lift the tissues and allow drainage of aqueous over the entire plate. The implants are MRI safe (Table 3.3).

Table 3.2 Specifications of the other AGV models available

3.2.4 Baerveldt Implant (Fig. 3.3)

3.2.2 Krupin Slit Valve

Other AGV models Single plate Double plate Silicone plate Polypropylene plate Size 96 mm2 Size 184 mm2 Size 364 mm2 Fig. 3.2 Molteno S-series single-plate implant

S2, FP7, M4 B1, FX1 FP7, FP8, FX1, PC7, PC8 S2, S3, BI, M4, PS2, PS3 S3, FP8, PS3, PC8 S2, FP7, PS2, PC7 B1, FX1

Baerveldt implant is a silicone tube implant attached to a soft, pliable, barium-impregnated silicone end plate of various sizes (i.e., 250 mm2, 350 mm2, or 500 mm2). This was introduced by Baerveldt in 1992 [15, 16]. The end plate has fenestrations which allow fibrous septa to develop that reduces the movement of the bleb.

SS

Surface Area of Plate = 185 mm2

SL

Surface Area of Plate = 245 mm2

B. Sharma et al.

16 Table 3.3  Specifications of Molteno implant Molteno implants Molteno3 S-series SS Molteno3 S-series SL Molteno3 G-series GS Molteno3 G-series GL Molteno S1 Molteno Pediatric P1 Molteno L2 and R2 Molteno pressure ridge D1 Molteno pressure ridge DL DR

Plate Single plate Single plate Single plate Single plate Single plate Single plate Double plate Single plate Double plate

Size 185 mm2 254 mm2 175 mm2 230 mm2 133 mm2 80 mm2 266 mm2 133 mm2 266 mm2

Fig. 3.4  Baerveldt glaucoma implant BG 102-350 for pars plana insertion

cus in a pseudophakic eye or in pars plana in a vitrectomized eye (Fig. 3.4). AGV with pars plana clip (PS2, PS3) and Baerveldt BG 101-350 glaucoma implant are used as pars plana glaucoma drainage devices.

Fig. 3.3  Baerveldt BG 101-350 implant

AADI is a Baerveldt type implant manufactured in India.

3.2.5 Schocket Implant Schocket implant [17] is a silastic tube implant with 0.3  mm internal diameter. One end of the tube is inserted into the AC, and the other end is tucked beneath the groove portion of # 20 retinal encircling band attached 360° around the globe near the equator under the recti muscles.

3.2.6.1 Indications for Pars Plana GDD • Patients that require shunt surgery and have undergone (or are expected to need) corneal transplantation. • Patients that require shunt surgery and a vitrectomy is otherwise indicated include chronic uveitis and neovascular glaucoma are the conditions which require shunt surgery and vitrectomy. 3.2.6.2 Advantages of the Pars Plana Approach • Pars plana implant does not compromise the cornea. • Risk of retraction of the tube is less with pars plana approach. • Accurate positioning is less important with a pars plana device compared with an anterior chamber implant.

3.2.6 P  ars Plana Glaucoma Drainage Devices

3.3

The tube of the glaucoma drainage implant is most commonly placed in the anterior chamber. However, the tube may also be placed in the sul-

The conventional glaucoma drainage devices shunt the aqueous from the anterior chamber to the subconjunctival space and thereby help in

Summary

3  The Glaucoma Drainage Devices: Types and Models

17

maintain the IOP.  Various models are available, and they are chosen in accordance with the patient and disease profile. Newer devices are discussed in a separate chapter.

Ahmed Glaucoma Valve implant. Am J Ophthalmol. 1999;127:27–33. 10. Topouzis F, Coleman AL, Choplin N, et al. Follow-up of the original cohort with the Ahmed glaucoma valve implant. Am J Ophthalmol. 1999;128:198–204. 11. Cvintal V, Moster MR, Shyu AP, McDermott K, Ekici F, Pro MJ, Waisbourd M. Initial experience with the new Ahmed glaucoma valve model M 4: short-term results. J Glaucoma. 2016;25(5):e475–80. 12. Sluch I, Gudgel B, Dvorak J, Anne Ahluwalia M, Ding K, Vold S, Sarkisian S.  Clinical experience with the M4 Ahmed Glaucoma drainage implant. J Curr Glaucoma Pract. 2017;11(3):92–6.. Epub 2017 Oct 27 13. The Krupin Eye Valve Filtering Surgery Study Group. Krupin eye valve with disk for filtration surgery. Ophthalmology. 1994;101:651–8. 14. Airaksinen PJ, Aisala P, Tuulonen A. Molteno implant surgery in uncontrolled glaucoma. Acta Ophthalmol. 1990;68:690–4. 15. Britt MT, LaBree LD, Lloyd MA, Minckler DS, Heuer DK, Baerveldt G, et al. Randomized clinical trial of the 350-mm2 versus the 500-mm2 Baerveldt implant: longer term results: is bigger better? Ophthalmology. 1999;106:2312–8. 16. Hodkin MJ, Goldblatt WS, Burgoyne CF, Ball SF, Insler MS.  Early clinical experience with the Baerveldt implant in complicated glaucomas. Am J Ophthalmol. 1995;120:32–40. 17. Omi CA, De Almieda GV, Cohen R, et al. Modified schocket implant for refractory glaucoma. Experience of 55 cases. Ophthalmology. 1991;98(2):211–4.

References 1. Zorab A.  The reduction of tension in chronic glaucoma. Ophthalmoscope. 1912;10:258–68. 2. Stefansson J.  An operation for glaucoma. Am J Ophthalmol. 1925;8:681–92. 3. Muldoon WE, Ripple PH, Wilder HC.  Platinum implant in glaucoma surgery. Arch Ophthalmol. 1951;45:666. 4. Tronsco MU. Use of tantalum implants for inducing a permanent hypotony in rabbit eyes. Am J Ophthalmol. 1949;32:499–508. 5. Molteno ACB. New implant for draining in glaucoma. Br J Ophthalmol. 1969;53:609. 6. Molteno AC, Straughan JL, Ancker E, et al. Long tube implants in the management of glaucoma. S Afr Med J. 1976;50:1062–6. 7. Ayyala RS, Zurakowski D, Smith JA, et  al. A clinical study of the Ahmed glaucoma valve implant in advanced glaucoma. Ophthalmology. 1998;105:1968–76. 8. Coleman AL, Hill R, Wilson MR, et al. Initial clinical experience with the Ahmed Glaucoma Valve implant. Am J Ophthalmol. 1995;120:23–31. 9. Huang MC, Netland PA, Coleman AL, et  al. Intermediate-term clinical experience with the

4

Preparing the Patient for the Glaucoma Drainage Device Surgery Parul Ichhpujani

Medical and/or laser treatment are the first line of treatment for most glaucoma patients. However, if the target intraocular pressure (IOP) is not attained on maximally tolerable medical therapy and glaucomatous damage is still progressing or is deemed likely to progress, then surgery is suggested to the patient. Usually, the surgeon and the patient are faced with a dilemma to choose between a trabeculectomy and a glaucoma drainage device. Patients scheduled for any surgery are apprehensive and have lots of queries. Clinicians can enhance patient preparation by explaining the need for the suggested surgery, available alternatives and what to expect from the surgery and reinforcing instructions as regards preoperative fasting (especially in cases undergoing general anaesthesia and for diabetics), medications (e.g. aspirin, oral hypoglycaemics, antihypertensives), anaesthesia and postoperative care.

glaucomas that have failed medical and laser therapies in addition to one or more surgical procedures such as trabeculectomy [1]. In recent years, some surgeons have forgone standard trabeculectomy surgery and started using GDDs or tube shunts as first-line surgery [2, 3]. Patient must understand that a GDD surgery will not result in improvement in vision; rather the chief reason for performing the procedure is preventive as without it, vision is likely to deteriorate or, in rare cases, be totally lost. For most patients, the benefits of the surgery outweigh the risks, but this has to be evaluated separately for each patient.

4.1

Trabeculectomy: If prior trabeculectomy has not been performed, then trabeculectomy may be considered as an option. The Tube Versus Trabeculectomy (TVT) Study has shown that both the procedures resulted in a significant reduction in IOP that was sustained even at the 5-year follow-up, with a significant reduction in the use of supplemental antiglaucoma medicines in both the groups. Early postoperative complications were more frequent in the trabeculectomy group, though

 hat Are the Indications W for Glaucoma Drainage Device (GDD) Surgery?

Glaucoma drainage devices or tube shunts are employed as a surgical procedure to control IOP in primary or secondary, open-angle or angle-­closure P. Ichhpujani (*) Glaucoma Service, Department of Ophthalmology, Government Medical College and Hospital, Chandigarh, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_4

4.2

 hat Are the Alternatives W to Glaucoma Drainage Device Surgery?

19

P. Ichhpujani

20

most were transient and self-limited. Late postoperative complications, resurgery for complications, cataract extractions and vision loss were not statistically different between the two groups [3]. Cyclodestructive procedures: Cyclodestruction using cryotherapy is associated with visionthreatening complications and hence is no longer considered a preferred option. Cyclodestruction by diode laser cyclophotocoagulation (DLCP) is an option in refractory cases with poor functional vision. It is achieved by transcleral application of infrared light, which is mainly absorbed at the site of aqueous production, pigmented epithelial cells of the ciliary body resulting in the destruction of ciliary body epithelium and coagulation necrosis of ciliary body stroma. Immediate and late complications of DLCP include corneal edema, hypotony and, rarely, phthisis bulbi. These days endocyclophotocoagulation (ECP) has emerged as an option for cyclodestruction under direct visualization. ECP is being used as a stand-alone procedure or in combination with phacoemulsification. ECP can be used in glaucoma patients with good visual potential. Most surgeons prefer GDDs over cyclodestructive procedures when patient has functional central vision (better than 20/100).

These GDDs do not have a restrictive valve device within them; hence, these need to be tied off (rip cord suture) at the time of surgery. Depending on the type of suture used, the ligature often spontaneously dissolves at around 6 weeks to allow flow from the tube to the plate. Some surgeons prefer a stent to block the tube, which when removed makes the GDD functional. Usually by 6 weeks, a thick capsule forms around the plate. Therefore, when aqueous passes through the tube, and to the plate, the capsule provides some resistance and helps prevent the IOP from being too low. Data from the Ahmed Versus Baerveldt (AVB) Study and the Ahmed Baerveldt Comparison (ABC) Study suggests that there are pros and cons to these two most commonly used GDDs [4, 5]. The choice of device is based on the surgeon’s skill and expertise and patients’ need. Some surgeons reserve AGV for refractory cases such as neovascular glaucoma or uveitic angle closure where IOP is markedly elevated and needs to be reduced quickly. But if moderate pressure can be maintained in the early postoperative period, Baerveldt is a good option. It has a lower profile than the AGV, and the 5-year treatment outcomes in the ABC Study show that IOP is slightly lower in the Baerveldt group [5].

4.3

4.4

 hich GDD Is Better: Valved W or Non-valved?

Valved drainage implants: These implants can potentially avoid low IOP/hypotony in the early postoperative period. Ahmed glaucoma valve (AGV) implant is currently the only valved GDD used. Non-valved drainage implants: Baerveldt drainage implant and Molteno drainage implant are two commonly used non-valved GDDs across the globe. India also has a cheaper alternative by the name of AADI (Aurolab aqueous drainage implant).

 hat Are the Basic W Investigations Required Prior to Surgery?

Preoperative optimization of medical conditions such as diabetes, hypertension and coronary disease is mandatory prior to scheduling the patient for a planned surgery. As a routine preoperative procedure, basic investigations that are carried out include haemoglobin, coagulogram, blood sugar, routine urine examination, ­electrocardiogram, etc. These help to identify undiagnosed systemic conditions requiring attention prior to surgery.

4  Preparing the Patient for the Glaucoma Drainage Device Surgery

4.5

 hich Drugs Should W Be Continued or Discontinued Prior to Surgery?

Prior to undergoing GDD surgery, all topical and systemic medications must be continued up until the morning of the surgery. Blood-thinning medications such as aspirin, warfarin and clopidogrel should be discontinued at least 1 week before the surgery, to reduce the risk of any bleeding inside the eye. Patients who are taking warfarin are advised to have their level (INR) checked in the week prior to surgery to ensure it is within their usual treatment range. These may be restarted 3  days after surgery (unless otherwise stated). The prescribing clinician must be consulted to be sure if it is safe to discontinue these medications or switch to an alternative medication, especially if the patient has a history of recent heart valve replacement or other serious condition that may need to be taken into consideration. These patients can be operated under monitored anaesthesia care (MAC).

4.6

 hat Type of Anaesthesia Is W Given for a GDD Surgery?

Most cases can be operated under the effect of peribulbar anaesthesia, with or without a mild sedative. In special circumstances, general anaesthesia may be preferable. General anaesthesia is also preferable for patients who are claustrophobic or have back or breathing problems. The surgical procedure usually lasts about an hour and a half.

4.7

What to Expect in the Postoperative Period?

The eye is patched after the surgery, and the patch is removed the following day. If the unoperated eye has poor vision, then the operated eye is not patched with a cotton pad. Instead, a clear shield is placed on the operated eye so that patient can

21

function after surgery. Shield is also advised at bedtime to prevent pressure over the globe. The postoperative eye drops usually consist of an antibiotic and steroid eye drop. Initially, the steroids need to be used intensively (about six times daily) and the antibiotic four times daily. In case of frequent instillation, the drops are usually intended to be instilled during the day (waking hours) only. If overnight intensive use is intended, then the patient must be instructed specifically. Topical medications for the unoperated eye must be continued unless advised otherwise. Patients are seen on the first postoperative day and then once a week for the first 4  weeks and may be seen more frequently if the IOP is either elevated or too low or bleb is showing signs of impending failure. The postoperative eye drops need to be taken for 1 or 2 months.

4.8

 hat Are the Possible Risks W and/or Complications?

Majority of tube shunt procedures are successful and relatively halt the glaucoma progression to blindness. Nonetheless, it is important to understand the possible risks and complications associated with GDDs. Any of the complications listed underneath can occur even with the best surgical techniques. Most of the complications are short-­ lived or can be conservatively or surgically managed, while serious complications are much more rare. The principal long-term complication of an anterior chamber GDD is corneal endothelial decompensation. Other common postoperative issues include: • Transient hypotony: This usually results due to leak around the tube in limbal tissues or failure of flow-restricting devices to maintain sufficient resistance. • Postoperative hypertensive phase: This is usually seen 2–3  weeks post surgery. IOP increases due to inflammation induced by flow of aqueous humour around the explant, necessitating resumption of topical antiglaucoma medications.

P. Ichhpujani

22

Uncommon or rare complications include: • Choroidal detachment. • Intraocular bleed. • Infection: With a GDD surgery, infection can occur months to years after the surgery and may sometimes necessitate GDD removal. Postoperative instructions usually address in detail how to prevent late infections. • Diplopia: Seen with larger GDDs such as Baerveldt. • Tube-related complications: Tube-cornea touch, tube extrusion and tube exposure.

4.9

 hat Is the Success Rate W of GDD Surgery?

• With GDDs such as the Baerveldt, the expected success rate over 5 years is as high as 70% and 80% [4, 5]. Although a significant proportion of patients achieve adequate IOP control without the need for antiglaucoma medications, many may still require one or two medications to assist the shunt in controlling the IOP. • Any GDD surgery may fail over a period of time, due to the natural wound healing tendencies of the eye. The body reacts to the GDD as a “foreign object” and results in fibrosis and scarring around the plate of the GDD.  As a result, glaucoma medications may need to be resumed or stepped up to lower the elevated IOP. Additionally, sometimes a repeat surgery may be required. On the flip side, non-valved GDDs may cause hypotony, which may result in vision impairment and thus may require a revision procedure.

4.10 W  hich Day-to-Day Activities Can Be Carried Out After a GDD Surgery? • Watching television, using a computer and reading can be continued without worry. If the intraocular pressure is very low, then patient

•

•

•

•

must refrain from all forms of exertion until the pressure is restored. Preferably the patient should wear an eye shield during sleep for the first postoperative week. While praying, patients may kneel but should refrain from bowing the head down to the floor in the first 2  weeks. Yoga asanas that require head-down posturing should also be avoided. It is important to avoid strenuous activity and sports such as swimming, jogging and contact sports, during the early postoperative period. It is recommended to commence strenuous activity only after consulting with the concerned surgeon. It is safe to fly after surgery, but it is best not too travel in the first 2 weeks after surgery as frequent follow-up visits may be scheduled in this period. If a patient wears contact lenses, it is possible to start wearing them again about 4–5 weeks after surgery and sometimes sooner.

4.11 W  hen Can the Patient Resume Work? The duration of time off work depends on a number of factors such as the nature of job, vision in the other eye and/or any postoperative complications. Typically, a patient working in an office environment can resume work in 2  weeks. If work entails heavy labour/weight lifting, or a dusty environment, then longer rest is needed.

4.12 W  hat Are the Chances of Infection with the Donor Tissue Used as a Patch Over the Tube of GDD? • The donor tissues used in GDD surgery are not live transplants. Donors are tested prior to receiving the tissue for infectious diseases such as HIV, hepatitis B and C and syphilis. • They are not tested for prion disease as no suitable test exists. The risk of transmission of

4  Preparing the Patient for the Glaucoma Drainage Device Surgery

prion disease has been documented to be extremely low. • In the United Kingdom, after receiving donor tissue, patients no longer remain eligible to donate blood.

4.13 A  re the GDDs Safe for MRI Scanning? AGV does not show up on an X-ray but is visible on a CT scan and MRI images. The Baerveldt implant is “radiopaque” (Barium impregnated) and shows up on all three imaging studies. Neither of these implants have any metal in them; therefore they both are safe for use with MRI scanning. One size does not fit all. Ultimately, “to trab or to tube” is the surgeon’s decision, but a well-­ informed patient will be more prepared and have realistic expectations from the surgery performed.

23

References 1. Hong CH, Arosemena A, Zurakowski D, et  al. Glaucoma drainage devices: a systematic literature review and current controversies. Surv Ophthalmol. 2005;50:48–60. 2. Gedde SJ, Schiffman JC, Feuer WJ, et al. The Tube Versus Trabeculectomy Study: design and baseline characteristics of the study patients. Am J Ophthalmol. 2005;140:275–87. 3. Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the Tube Versus Trabeculectomy (TVT) Study after five years of follow-up. Am J Ophthalmol. 2012;153(5):789–803. 4. Christakis PG, Tsai JC, Kalenak JW, Zurakowski D, Cantor LB, Kammer JA, Ahmed II. The Ahmed versus Baerveldt study: three-year treatment outcomes. Ophthalmology. 2013;120(11):2232–40. 5. Budenz DL, Barton K, Gedde SJ, Feuer WJ, Schiffman J, Costa VP, Godfrey DG, Buys YM, Ahmed Baerveldt Comparison Study Group. Five-year treatment outcomes in the Ahmed Baerveldt comparison study. Ophthalmology. 2015;122(2):308–16.

5

The Ideal Glaucoma Drainage Device: Which One to Choose? Purvi Bhagat

5.1

Introduction

The number of available surgical options for managing glaucoma is on the rise. Innovations in technology not only offer greater hope to patients but also force the surgeons to make difficult therapeutic decisions. The surgeons must critically evaluate each individual case and treatment options to determine which surgical measure would finally be the most appropriate. After the first glaucoma drainage device (GDD), i.e., the Molteno implant, was introduced, various modifications in design and improvements in surgical techniques have occurred leading to greater success with better pressure control, easier implantation, and fewer complications [1]. With implantation of a GDD into the episcleral space and placement of its silicone tube either into the anterior chamber or pars plana, the aqueous humor is drained from the eye under the Tenon’s capsule and conjunctiva, leading the fluid to the base plate. Placed near the equator of the eye, this plate leads to a cyst formation that provides resistance to fluid transport, ultimately leading to reduction of intraocular pressure (IOP) (Fig. 5.1) [2]. Currently, the GDD are available in various sizes, materials, and designs and with or without P. Bhagat (*) M & J Western Regional Institute of Ophthalmology, B. J. Medical College and Civil Hospital, Ahmedabad, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_5

an IOP regulating valve. The conventional ones are the Molteno, Krupin, Baerveldt, Ahmed glaucoma valve (AGV), and Aurolab aqueous drainage implant (AADI). There are also newer devices like the Ex-Press mini shunt, Glaukos iStent, OptiMed Glaucoma Pressure Regulator, and gold micro shunt. These are positioned in the anterior chamber angle from where they either drain the aqueous into the Schlemm’s canal, subconjunctival space, or the suprachoroidal space. Fluid exits the eye onto plate Cornea

Iris

Tube

Plate

Fig. 5.1  Principle of a glaucoma drainage device 25

P. Bhagat

26 Table 5.1  Glaucoma drainage devices [1, 3] Type Valved implants •  Ahmed implant  Single plate   Pediatric size   Double plate   Pars plana   Pars plana (pediatric) •  Krupin slit valve • OptiMed Non-valved implants • Baerveldt   Single plate   Pars plana •  Eagle vision • Molteno   Single plate   For microphthalmos   Double plate   Molteno 3/single plate   Molteno 3/double plate •  Aurolab aqueous drainage implant (AADI)

Size

Material

184 mm2 96 mm2 364 mm2 184 mm2 96 mm2 183 mm2 140 mm2

Polypropylene/silicone Polypropylene/silicone Polypropylene/silicone Polypropylene/silicone Polypropylene/silicone Silastic Silicon + polymethylmethacrylate

250/350 mm2 350 mm2 365 mm2

Silicone Silicone Silicone

137 mm2 50 mm2 274 mm2 175 mm2 230 mm2 350 mm2

Polypropylene Polypropylene Polypropylene Polypropylene Polypropylene Silicone

The drainage devices most frequently used are the AGV, AADI, and Ex-Press (Table 5.1). With the gradual increase in the use of these implants, it is important to be aware of their merits and demerits so that the most appropriate can be selected for a given case. Unfortunately, there is inadequate evidence suggesting that one particular shunt is the best choice for a specified given diagnosis [4]. However, some guidelines maybe formed that maybe useful in selecting one implant over another. These guidelines are based on various comparative studies done on different devices and aim to answer the following questions: 1. Do all the glaucoma drainage implants lower the pressure equally? 2. Do larger implants lower the IOP more than smaller ones? 3. Does the design of the implant influence the complications? 4. Do indications for various devices differ?

5.2

Comparison of Glaucoma Drainage Devices

Although the drainage implants are used so very frequently, almost all comparisons have been

retrospective and nonrandomized and have compared different device models in different patient populations using different criteria for success and for variable follow-ups [3]. • An important conclusion to be remembered from the study of Mills et al. was that a 10% failure rate existed per postoperative year in a series including long-term follow-up for single- and double-plate Molteno tubes. Extrapolating the data, it seems that most GDDs have a functional life span of less than 5 years before they fail from fibrous encapsulation [5]. • A meta-analysis of 147 studies published between 1966 and 2002 was carried out by Hong et  al. [5]. Fifty-four articles were included in the final analysis (29 with Molteno, single and double plate with some intraoperative modification to prevent hypotony, with single-plate Molteno without any surgical modification, 9 with Baerveldt, 8 with AGV, and 2 with Krupin). It was concluded that all the five implants significantly lowered IOP but there was no statistically significant difference between the percentage change in pressures and in the overall surgical success between devices. It was also found that a

5  The Ideal Glaucoma Drainage Device: Which One to Choose?

larger end plate does not lower the IOP more than standard single plates when followed for more than a year [1, 6].

5.2.1 Comparison of Plate Size Plate size of various implants has also been analyzed and compared to understand whether it has any influence on the final IOP. • A randomized controlled trial involving 132 patients showed a higher success rate in the double-plate (270 mm2) Molteno group compared to the single-plate (135 mm2) Molteno group [3]. • The study by Heuer et  al. also showed improved IOP control with the Molteno double plate compared to the single plate in a prospective study of aphakic and pseudophakic glaucoma [1, 7]. • In a prospective study by Lloyd et al. comparing 350 mm2 and 500 mm2 Baerveldt implants, statistically comparable results were reported as regards IOP control, visual acuity, and complications [3, 8]. • In another similar prospective study comparing 350 mm2 and 500 mm2 Baerveldt implants, Britt et al. found better IOP control with the 350 mm2 implant than with the 500 mm2 [9]. • Although fewer IOP-lowering agents were required in patients with 500 mm2 implants to achieve target IOP, some complications also occurred more frequently with this size. A larger filtration area would appear to improve filtration, but the eventual subconjunctival fibrosis over a wider area may also have an adverse influence [3]. • A study comparing Baerveldt glaucoma implants (BGI) with end plate sizes of 250  mm2 and 350  mm2 concluded that there was no difference in surgical success, IOP, vision, or topical medications through 3 years [3, 10]. • In another retrospective study, double-plate Molteno showed a lower mean IOP compared to single-plate AGV at 24  months [1, 11]. The study also reported a high incidence of postoperative hypotony in the non-valved

27

group and hypertensive crisis in the valved group [12]. All these studies indicate that size of the implant does matter, but to a limited extent. As a general rule, the bigger the implant plate, the greater will be the risk of hypotony. Non-valved tubes are now temporarily tied off during implantation leading to little difference in rates of immediate postoperative hypotony between valved and non-valved glaucoma drainage devices [13].

5.2.2 Comparison of Plate Material Plate material has also been studied to assess its influence on IOP control, as it may affect the tissue reaction and degree of bleb encapsulation. Elastomeric silicone (polydimethylsiloxane) is the most commonly used material in current GDDs. Silicone, polymethylmethacrylate, and other hydrophobic polymers have a relatively higher binding affinity for plasma and interstitial fluid proteins. These proteins get adsorbed within minutes of implantation leading to cellular adhesion, cytokine release, and inflammation. Chronic low-grade inflammation is further exacerbated by microscopic shearing of the implant relative to the surrounding tissues [3]. • Ayyala et al. reported more inflammation with polypropylene variety (Molteno) than with silicone (Krupin implant) when inserted subconjunctivally in rabbits [14, 15]. • Retrospective studies comparing AGV silicone and polypropylene models reported similar results with both in terms of IOP control, final visual acuity, and postoperative use of antiglaucoma medications [16, 17]. In one of these studies, the silicone implant was associated with fewer serious complications [16]. • In a prospective, multicentric, comparative series, wherein the AGV silicone and polypropylene material were investigated, improved IOP control was seen with the silicone model compared to polypropylene. Tenon’s cysts were observed more in the polypropylene group [18].

P. Bhagat

28

Late postoperative hypotony caused by “overfiltration” can be managed by removing part of the plate in cases of silicone implant. This is not possible with Molteno or older AGVs made of rigid polypropylene material that cannot be cut easily. In summary, polypropylene end plates are more inflammatory than silicone. The inflammation may be due to the biomaterial itself, rigidity, flexibility, and shape of the end plate [15].

5.2.3 Comparison of Plate Design The design of the implant is also said to have an influence on the rate and type of complications. Ocular motility problems usually occur with larger plates but are not uncommon with smaller ones. Diplopia has been noted more with Baerveldt implants than with AGV or Molteno implant [1]. This extraocular muscle imbalance results mainly due to the mass effect of the plate and surrounding bleb on the neighboring extraocular muscles and due to the implant “wings” located beneath the muscles. Other aqueous shunts appear to have an incidence of diplopia in the range of 2–7% [13].

5.2.4 Comparison of AGV and Baerveldt Device • A few retrospective studies have compared the AGV and Baerveldt implants. One series consisting of 118 eyes and followed up for 48 months found that the final success in terms of IOP control was comparable in both groups. Hypotony-related complications were seen more in the Baerveldt group, and hypertensive crisis requiring antiglaucoma medications was more in the Ahmed group [19–21]. • The Ahmed Versus Baerveldt (AVB) study evaluated 238 patients with uncontrolled refractory glaucoma. The Baerveldt group had a lower IOP than the Ahmed group (13.6 vs. 16.5  mmHg) at the end of 1  year and used fewer glaucoma medications (1.2 vs. 1.6) but required more postoperative surgical interventions [22, 23].

• The Ahmed Baerveldt Comparison (ABC) study, a multicentric, randomized, prospective trial wherein 276 patients with uncontrolled glaucoma received either an AGV (model FP7) or a Baerveldt implant (model 350 mm2), reported that 1  year postoperative, the Baerveldt group had a lower IOP than the Ahmed group (13.2 vs. 15.4  mmHg), had lesser additional surgeries required, and used lesser glaucoma medications (1.5 vs. 1.8). The incidence of early and serious postoperative complications, however, was more common in the Baerveldt group [23, 24]. • In another study, devastating hypotony-related complications occurred only in Baerveldt implanted eyes resulting in poor visual outcomes. Bleb encapsulation was significantly more common in the Ahmed group (11% vs. 3%). Interventions were needed significantly more often in Baerveldt eyes than the Ahmed valve eyes (47% vs. 32%) [25]. • Barton et al. concluded that the Ahmed valve offers improved predictability of early control, while the Baerveldt implant has a lower rate of long-term excessive encapsulation [26, 27]. • Budenz et al. found no difference between the success rates of the Ahmed and the Baerveldt system after 1 year of follow-up [24, 28].

5.2.5 Comparison of Cost Another important consequence of a tube surgery which is of concern and has to be borne in mind is the cost of post-surgery glaucoma medications. Because the Baerveldt and its prototypes are non-­ valved devices, enough pressure control is not obtained until the tube ligation suture dissolves. So during this period, there is a need for glaucoma medications to control the IOP.  Using an Ahmed valve might eliminate this extra cost [29].

5.3

Selection of the Shunt

The decision to choose a specific device depends on the patient’s disease characteristics like type of glaucoma, preoperative IOP, optic nerve damage, and target IOP. It also depends on patient’s

5  The Ideal Glaucoma Drainage Device: Which One to Choose?

age and compliance and the surgeon’s personal comfort and choice. The general guidelines which may be considered during decision-making are: 1. For a novice surgeon, valved devices may be preferred as the surgical technique is simpler involving one quadrant and without manipulation of muscles. IOP control in the early postoperative period is also more predictable with the flow-restricting mechanism. Postoperative care is simplified with minimal risk of hypotony and choroidal effusion. 2. The valved shunts are highly effective for eyes that need a low IOP quickly, such as in cases of advanced open-angle glaucoma, uveitic glaucoma, and neovascular glaucoma. If an eye can tolerate a higher IOP for few weeks even after surgery, then a Baerveldt type implant may be considered. 3. In patients showing poor compliance with drug use and follow-ups, valved implants may be preferred which usually require less postoperative follow-up and care. Because the tube in non-valved devices is occluded during the initial 4–6 weeks, it often requires added interventions, medicines, and follow-ups [30]. 4. In patients with high risk of suprachoroidal hemorrhage, including those with aphakia, previous vitrectomy, uncontrolled blood pressure, or very high preoperative IOP and who use anticoagulants, valved implants maybe safer because of the reduced risk of IOP fluctuations [31]. 5. The non-valved type may be preferable if an Ahmed device has already failed in the eye [23]. 6. Although the Baerveldt types may provide lower long-term pressures, there are pressure instabilities in the early postoperative period that may not be acceptable to patients with severe disease. 7. The amount of conjunctival scarring may also determine the size of the implant and available area for a single-plate versus double-plate device. 8. The most important factor influencing the selection of implant is the target IOP, both in the short term and long term.

29

Early IOP control is determined by the presence or absence of valve in an implant. Valved implants provide more immediate IOP control and a lower rate of hypotony. Long-term IOP control depends on the surface area of the implant, which determines the bleb size, tissue response to implant, and thickness of the fibrous capsule which controls the aqueous flow through the bleb wall [32–34]. If the postoperative target IOP is relatively higher, one might choose an Ahmed valve because the risk to the patient is less. If the patient is younger, with concerns about healing and bleb encapsulation, then the choice would be a Baerveldt type. If a patient is elderly with a failed trabeculectomy, the choice would be an Ahmed for safety reasons and considering the life expectancy of the patient. If a patient has had a failed trabeculectomy, followed by interventions and finally a failed filter, and the conjunctiva is unhealthy, a Baerveldt type should be considered [30]. 9. Implant size: The ideal size of the end plate is unknown, and research shows conflicting data [35]. There is also no current evidence to suggest that when a larger plate is needed, which is better, single large plate or double plates [4]? Advantage of single plate: Ease of insertion. Advantages of double plate: Egress of aqueous to either plate can be controlled by ligating the connecting tube, thus independently controlling the flow of aqueous to each plate. Disadvantages of single plate: There is no role of individual ligation. Larger plates are also more prone to hypotony and its related complications. Disadvantages of double-plate implants: These include difficulty of insertion, and if they fail, the upper quadrants are unavailable for future reuse. The use of smaller surface implants may achieve similar IOP lowering effect and with the added advantage of fewer complications, and with preservation of one of the upper quadrants for further repeat glaucoma surgery, if needed.

P. Bhagat

30

5.4

Tubes Versus Ex-Press Shunt

5.4.1 Indications for Tubes [36, 37] • Very high baseline IOP with a relatively higher postoperative target IOP. • Steroid response glaucoma—This condition usually presents with very high IOP but is often also short lived. A tube shunt can control the IOP during the required period, and the spike resolves by the time the tube shunt enters the hypertensive phase. • Absence of healthy superior bulbar conjunctiva for an Ex-Press shunt or a trabeculectomy. • Patients who are not likely to comply with visits either due to distance issues or due to lack of support system to help with visits and postoperative instructions or due to associated co-morbidities. • Patients with history of corneal transplant—It is proven that tube shunts placed in anterior chamber don’t do as well in patients with penetrating keratoplasty and vice versa. Unfortunately, the Ex-Press is much less likely to succeed in the presence of a shallow anterior chamber and/or peripheral anterior synechiae. Trabeculectomy is also highly likely to fail even with adjuvant use of antimetabolites. So tube shunts placed in the pars plana are the best choice in these patients. • Patients with blepharospasm, severe squeeze reflex, or very poor exposure of the superior bulbar conjunctiva as in inability to infraduct the eye, very small palpebral fissure, or prominent brows wherein bleb care and bleb interventions would be extremely difficult. • Patients with poor visual potential especially in cases of uveitic or neovascular glaucoma where the inflammation is more likely to complicate the postoperative period. • Monocular patients, especially elderly, unless there is a need for IOP less than 12 mmHg. • Patients with narrow angles or angles closed with synechiae—Since a peripheral iridectomy is not performed with the Ex-Press shunt, in phakic patients with narrow angles,

•

•

• •

postoperative shallow anterior chamber and aqueous misdirection occur more commonly. Patients who did poorly in the other eye with a prior trabeculectomy and did well with a subsequent tube shunt. Patients with severe dry eye disease who might not tolerate an anterior bleb and possibly have bleb dysesthesia. Patients who wish to continue wearing contact lenses postoperatively. Patient preference.

5.4.2 I ndications for Ex-Press Shunt [38, 39] 1. Sturge-Weber syndrome—Since choroidal effusions are common in these patients, Ex-­ Press offers a safer alternative because of its lower rate of prolonged postoperative hypotony. 2. Angle recession glaucoma—Because of the minimal tissue manipulation and quieter postoperative course with the Ex-Press. 3. Patients with impaired coagulation or on systemic anticoagulant drugs—Because it avoids an iridectomy, which often has associated bleeding. 4. Patients who have an urgent need for faster recovery. 5. Patients with very high preoperative pressures.

5.4.3 Contraindications for Ex-Press Shunt [40, 41] 1. Congenital and juvenile glaucoma—The long-term complications of Ex-Press shunt are still not clearly known in these cases, and so it is best avoided. 2. Aniridia and anterior segment dysgenesis syndrome—Angle structures being abnormal, Ex-Press implantation is best avoided. 3. Phakic primary angle closure glaucoma— Ex-­Press should be implanted in eyes with primary angle-closure disease only if simultaneous lens extraction is planned or in aphakic

5  The Ideal Glaucoma Drainage Device: Which One to Choose?

or pseudophakic patients. Presence of a shallow anterior chamber and a thick lens can end up in numerous postoperative complications. 4. Microphthalmos and nanophthalmos— because of shallow anterior chamber and smaller and crowded anterior compartment. 5. Pseudophakic glaucoma with the presence of an anterior chamber intraocular lens. 6. Neovascular glaucoma—The postoperative hyphema and blood clots can totally occlude the Ex-Press implant orifice. Also, severe postoperative inflammation may lead to adhesions of the scleral flap impairing filtration. 7. Patients with thin sclera. Although the effect of Ex-Press device lasts longer, it has to be remembered that it is more expensive than other treatment options [42].

5.5

 urolab Aqueous Drainage A Implant

All modern drainage implants are cost prohibitive to some extent for the general population. The AADI is a non-valved Baerveldt 350 type of device made of silicone elastomer. Manufactured by an Indian company, it is a low-cost alternative which can be of great use in poor communities, in the developing world, and in those individual patients where expense of treatment is a concern.

5.6

Other Shunts

Other newer shunts are still to be well evaluated individually and in comparison with other existing devices before we can comment on their uses.

5.7

Conclusion

There is no high-quality evidence which can support the statement that one drainage device is better than another for long-term IOP control. Design modifications and improvements in surgical technique are improving the outcomes and

31

minimizing the complications. Careful preoperative screening, proper planning, and a meticulous surgery can further help to improve the results [1]. Selecting a device should always be individualized, considering the profiles of each device, the surgeon’s own experience, patient’s treatment goals, the complete clinical situation, and the economic status of the patient.

References 1. Singh P, Kuldeep K, Tyagi M, Sharma PD, Kumar Y.  Glaucoma drainage devices. J Clin Ophthalmol Res. 2013;1:77–82. 2. Thieme H.  Glaucoma drainage devices. Ophthalmologe. 2009;106(12):1135–46. 3. Lim KS, Allan BDS, Lloyd AW, et  al. Glaucoma drainage devices; past, present, and future. Br J Ophthalmol. 1998;82:1083–9. 4. Caprioli J, Law SK, Giaconi JAA. Pearls of glaucoma management. Berlin: Springer; 2010. p. 296. 5. Mills RP, Reynolds A, Emond MJ, et  al. Long-term survival of Molteno glaucoma drainage devices. Ophthalmology. 1996;103:299–305. 6. Hong CH, Arosemena A, Zurakowski D, Ayyala RS.  Glaucoma drainage devices: a systematic literature review and current controversies. Surv Ophthalmol. 2005;50:48–60. 7. Heuer DK, Lloyd MA, Abrams DA, Baerveldt G, Minckler DS, Lee MB, et  al. Which is better? One or two? A randomized clinical trial of single-plate versus double-plate Molteno implantation for glaucomas in aphakia and pseudophakia. Ophthalmology. 1992;99:1512–9. 8. Lloyd MA, Baerveldt G, Fellenbaum PS, et  al. Intermediate-term results of a randomized clinical trial of the 350 versus the 500 mm2 Baerveldt implant. Ophthalmology. 1994;101:1456–64. 9. Britt MT, LaBree LD, Lloyd MA, Minckler DS, Heuer DK, Baerveldt G, et al. Randomized clinical trial of the 350-mm2 versus the 500-mm2 Baerveldt implant: longer term results: is bigger better? Ophthalmology. 1999;106:2312–8. 10. Rodgers CD, Meyer AM, Sherwood MB. Relationship between Glaucoma drainage device size and intraocular pressure control: does size matter? J Curr Glaucoma Pract. 2017;11(1):34. 11. Ayyala RS, Zurakowski D, Monshizadeh R, Hong CH, Richards D, Layden WE, et  al. Comparison of double-plate Molteno and Ahmed glaucoma valve in patients with advanced uncontrolled glaucoma. Ophthalmic Surg Lasers. 2002;33:94–101. 12. Molteno ACB. New implant for drainage in glaucoma: clinical trial. Br J Ophthalmol. 1969;53:606–15. 13. David R. Risks of Glaucoma drainage devices. 2014.

32 14. Ayyala RS, Harman LE, Michelini-Norris B, et  al. Comparison of different biomaterials for glaucoma drainage devices. Arch Ophthalmol. 1999;117:233–6. 15. Ayyala RS, Michelini-Norris B, Flores A, et  al. Comparison of different biomaterials for glaucoma drainage devices: part 2. Arch Ophthalmol. 2000;118:1081–4. 16. Mackenzie PJ, Schertzer RM, Isbister CM.  Comparison of silicone and polypropylene Ahmed glaucoma valves: two-year follow-up. Can J Ophthalmol. 2007;42:227–32. 17. Brasil MVOM, Rockwood EJ, Smith S. Comparison of silicone and polypropylene Ahmed glaucoma valve implants. J Glaucoma. 2007;16:36–41. 18. Ishida K, Netland PA, Costa VP, et al. Comparison of polypropylene and silicone Ahmed glaucoma valves. Ophthalmology. 2006;113:1320–6. 19. Syed HM, Law SK, Nam SH, et  al. Baerveldt-350 implant versus Ahmed valve for refractory glaucoma: a case-controlled comparison. J Glaucoma. 2004;13:38–45. 20. Wang JC, See JL, Chew PT.  Experience with the use of Baerveldt and Ahmed glaucoma drainage implants in an Asian population. Ophthalmology. 2004;111:1383–8. 21. Tsai JC, Johnson CC, Kammer JA, et al. The Ahmed shunt versus the Baerveldt shunt for refractory glaucoma II: longer-term outcomes from a single surgeon. Ophthalmology. 2006;113:913–7. 22. Christakis PG, Kalenak JW, Zurakowski D, Tsai JC, Kammer JA, Harasymowycz PJ, Ahmed II.  The Ahmed Versus Baerveldt study: one-year treatment outcomes. Ophthalmology. 2011;118(11):2180–9. 23. Boris D, Anjali SH.  Advice on glaucoma drainage devices: glaucoma today. 2012:49–51. 24. Budenz DL, Barton K, Feuer WJ, Schiffman J, Costa VP, Godfrey DG, Buys YM, Ahmed Baerveldt Comparison Study Group. Treatment outcomes in the Ahmed Baerveldt Comparison Study after 1 year of follow-up. Ophthalmology. 2011;118(3):443–52. 25. Ike A, Panos GC, James T. Study compares drainage devices: pros, cons provide insight into role of these implants in treatment of refractory glaucoma. 2012. 26. Barton K, Heuer DK.  Modern aqueous shunt implantation: future challenges. Prog Brain Res. 2008;173:263–76.

P. Bhagat 27. Tarek S, Shibal B.  Surgical management of glau coma: evolving paradigms. Indian J Ophthalmol. 2011;59(Suppl 1):S123–30. 28. Theime H. Current status of epibulbar anti-glaucoma drainage devices in Glaucoma surgery. Dtsch Arztebl Int. 2012;109(40):659–64. 29. Fran Smith M. The cost factor: tubes vs trabs redux. Rev Ophthalmol. 2009. 30. Ahmed IK, Christakis PG.  Ahmed, Baerveldt or something else? Rev Ophthalmol. 2013. 31. Kahook M, Shuman JS.  Chandler and grant’s glaucoma. 5th ed. Thorofare, NJ: Slack Inc.; 2013. p. 582–3. 32. Yvonne O. Glaucoma surgery series: tube shunts—a new drainage device for glaucoma. 2014. 33. David R.  Does it matter which glaucoma drainage device is implanted? 2014. 34. Aminlari AE, Scott IU, Aref AA.  Glaucoma drainage implant surgery—an evidence-based update with relevance to Sub-Saharan Africa. Middle East Afr J Ophthalmol. 2013;20:126–30. 35. Richard Z, Angela G.  An OD’s guide to Glaucoma surgery: some patients will opt for drainage implants or other procedures. How will they impact how optometrists monitor and treat? Rev Optom. 2015. 36. Catoira Boyle Y.  Mini-shunts vs. traditional shunts in practice which to use: when and why. Ophthalmol Manag. 2012;16:60–4. 37. Chen TC.  Surgical techniques in ophthalmology series: glaucoma surgery. Elsevier Health Sciences. 2007:63. 38. Mayer HR, Lin JL.  New technologies for treating Glaucoma in patients undergoing cataract surgery. Eur Ophthal Rev. 2009;3(2):44–8. 39. Emerick GT.  Highlights of the American glaucoma society. Glaucoma Today. 2013:55–6. 40. Angmo D, Temkar S, Saini M, Aggarwal R, Dada T. The Ex-PRESS Glaucoma drainage device: current perspective. DJO. 2014;24:151–9. 41. Ichhpujani P, Moster MR.  Novel glaucoma surgical devices, glaucoma–basic and clinical concepts. In: Shimon R, editor. 201:417–442. http://www.intechopen. com/books/glaucoma-basic-and-clinical-concepts/ novel-glaucoma-surgical-devices. 42. Liu J-H, Lin H-Y, Tzeng S-H, Chao S-C. Comparison of trabeculectomy with Ex-PRESS shunt implantation in primary-open-angle-glaucoma patients: a retrospective study. Taiwan J Ophthalmol. 2015;5:120–3.

6

Surgical Technique of Implantation: AGV, Limbal Variant Shibal Bhartiya and Monica Gandhi

6.1

Introduction

Ahmed Glaucoma Valve (AGV) is a drainage device used for both primary and refractory glauomas. The surgical technique of AGV implantation is simpler and easier than that for non-valved implants since the implant is limited to one quadrant and does not require manipulation of the recti muscles. Also, since the AGV is valved, manoeuvres like tube ligation and/or tube slits are not required. Because of this the incidence of hypotony in the early postoperative period is less than with nonvalved implants, and these patients require relatively less postoperative follow-up and care. Common complications, as with all restrictive valve implants, include longer postoperative hypotensive phase, choroidal effusions and flat anterior chambers (Table 6.1).

Electronic Supplementary Material  The online version of this chapter (https://doi.org/10.1007/978-981-13-57732_6) contains supplementary material, which is available to authorized users. S. Bhartiya Department of Ophthalmology, Fortis Memorial Research Institute, Gurgaon, India M. Gandhi (*) Anterior Segment and Glaucoma Services, Department of Ophthalmology, Dr. Shroff’s Charity Eye Hospital, New Delhi, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_6

6.2

Indications and Contraindications

The Ahmed glaucoma valve may be considered for glaucomas resistant to maximal medical therapy and in patients with failed glaucoma filtration surgeries. Valves are first-line procedure of the following: • • • •

Post-keratoplasty glaucoma. Neovascular glaucoma. Post-vitreoretinal surgery glaucoma. Phakic/aphakic glaucoma.

AGV implantation is contraindicated/considered high risk in eyes with aniridia and limbal stem cell deficiency since these patients have a high risk of tube extrusion. AGV must be used with caution in elderly patients in whom Tenon’s capsule is ultra-thin, and in patients with chronic uveitis, where the risk of chronic hypotony from the inflammation is higher.

6.3

Surgical Technique

This surgical technique can be used for all AGV models (Table  6.1), except for the rarely used double-plate AGV.  The technique for the FX1 model is similar to that used for double-plate non-valved implants in terms of isolation of recti 33

S. Bhartiya and M. Gandhi

34 Table 6.1  Types of AGV Type Ahmed glaucoma valve Single plate Paediatric size Double plate Single plate Paediatric size Double plate Pars plana Pars plana (Ped) Pars plana Pars plana (Ped)

Model

Size

Material

S2 S3 B1 FP7 FP8 FX1 PS2 PS3 PC7 PC8

184 mm2 96 mm2 364 mm2 184 mm2 96 mm2 364 mm2 184 mm2 96 mm2 184 mm2 96 mm2

Polypropylene Polypropylene Polypropylene Silicone Silicone Silicone Polypropylene Polypropylene Silicone Silicone

(Source: Table modified from http://eyewiki.aao.org/Glaucoma_Drainage_Devices)

and fixation of plates. It however does not require manoeuvres like tube ligation and/or tube slits.

6.3.1 Corneal/Limbal Traction Suture Following strict surgical asepsis, a corneal traction suture is placed using 8′0 Vicryl on a spatulated needle and clamped to the surgical drapes to provide adequate exposure of the surgical field. In case the surgeon prefers a limbal traction suture, the same is placed after the peritomy. Some surgeons prefer to use 6.0 silk suture for the corneal traction. Applying a superior rectus suture depends upon the eye as sometimes it may be considered to provide a wider working field.

6.3.2 Conjunctival Peritomy A 90° fornix-based conjunctival incision is made in the superotemporal quadrant. Following blunt dissection to separate the conjunctiva from the Tenon’s capsule, radial relaxing incisions may be made if required, to provide adequate surgical exposure. Care must be taken to extend the dissection towards the equator. The superotemporal quadrant is chosen for ease of surgical access and a lower incidence of ocular motility disorders. The second choice is the inferonasal quadrant, which is especially preferred in cases with silicone oil glaucoma.

6.3.3 Priming the AGV The AGV is primed at a site away from the surgical field, by injecting balanced salt solution (BSS) with a 30G needle through the tube. The valve is ready for use once BSS is seen coming out of the valve in a steady stream. Care must be taken to not damage the valve mechanism which is housed within the scleral plate.

6.3.4 Anchoring the Plate The plate is sutured 8–10  mm posteriorly from the limbus in the superotemporal quadrant and 6–8 mm posterior to the limbus in the nasal quadrants using preplaced 6-0 Dacron/7-0 silk sutures or 9-0 monofilament nylon suture. It is advisable to mark the position of the implant on the sclera using gentian violet.

6.3.5 Trimming the Tube The length of the tube within the anterior chamber should be approximately 2  mm. The tube is therefore trimmed to the desired length after the body of the valve is anchored to the sclera. Care must be taken that tube is cut with the bevel-up. This minimises the risk of tube occlusion by the iris and also minimises endothelial loss.

6  Surgical Technique of Implantation: AGV, Limbal Variant

6.3.6 Anterior Chamber Paracentesis An anterior chamber paracentesis is then performed superiorly using a 23G needle. Care should be taken to ensure that the AC entry is parallel to the plane of the iris and not placed too anteriorly or posteriorly. The former can result in endothelial decompensation due to rubbing of the tube against the cornea, while the latter carries the risk of persistent uveitis due to iris chafing/touch.

6.3.7 Tube Insertion The tube is then inserted through the needle track using an inserter or atraumatic forceps. In case the insertion is difficult, the track maybe inflated with viscoelastic to facilitate tube insertion and reformation of the AC.

6.3.8 Scleral Patch Graft The scleral patch graft (or donor pericardium) is trimmed to size and sutured to the sclera so that it covers the tube close to the limbus with 9-0/10-0 monofilament nylon. Note: Pars plana implantation of the AGV: Vitrectomy is done, and through the port the tube can be inserted or an AC paracentesis is done 3  mm posterior to limbus, and then the tube is inserted. A pars plana clip can be used to anchor the tube and prevent kinking.

6.3.9 Closing the Peritomy The conjunctival flap is then sutured over the implanted tube shunt using 8′0 Vicryl. Continuous, locking sutures ensure a watertight closure.

6.4

Alternate Techniques

1. Scleral flap technique: A partial-thickness scleral flap is dissected along the course of the

35

tube, in the shape of a rectangle with a lateral hinge. The tube is inserted into the AC as described above, and the flap is then positioned over it. The ends of the flap are sutured with 9-0/10-0 monofilament nylon. This technique provides better cosmesis than using a donor patch graft. Its use is however contraindicated in patients with scleral thinning. The tube maybe fixed with an “X” suture with 10-0 nylon to reduce its mobility and extrusion. 2. Scleral trench technique: A partial-thickness scleral flap is dissected along the course of the tube, in the shape of a rectangle with a lateral hinge. A deeper trench (1 × 9 mm) is then dissected to an approximate depth of 90% of the sclera. This tissue is then removed to fashion a deep scleral trench for the tube to nest in. The tube is positioned in the deep scleral trench and inserted into the AC. The partial-thickness scleral flap is sutured over the tube with 10-0 monofilament nylon, ensuring adequate tamponade. The tube maybe fixed with an X suture with 10-0 nylon to reduce its mobility and extrusion. 3 . Needle track technique: A bent 23G needle is used to make the needle track with the bevel­up, starting 4 mm behind the limbus. The needle is initially directed vertically under the episclera and then made parallel to the iris. As the needle enters the eye, viscoelastic is injected to avoid decompression and to decrease the risk of hypotony. The tube is then inserted through this needle track, which minimises lateral tube movements and, theoretically, erosions. This obviates the use of a scleral graft (donor or partial-thickness flap) and provides better cosmesis and reduces surgical time. The proponents of the technique also claim that it minimises the problems related to tube movements like erosions and extrusions. 4 . 24G needle track: In order to minimise the chances of a peri-tube leakage and consequent hypotony, some surgeons prefer to use a 24G needle for AC paracentesis. This ensures a snug fit of the needle track around the tube, resulting in cuffing of the AGV tube at the point of AC entry.

S. Bhartiya and M. Gandhi

36

6.5

Efficacy of AGV

The efficacy of the AGV valve as a treatment option for refractory glaucoma is dependent on the pathology for which it is implanted and the time period since the surgery. Different authors have quoted success rates ranging between 43% and 84% [1–7]. At 1 year the efficacy determined was 78% by Coleman et al. [2] In an Indian study by Das et al., the effectivity to control IOP was 53% at year 1, and this decreased to 43% by the second year [3]. It is postulated that a 10% decrease in efficacy occurs within a year and by 5 years it would be expected that the implant is effective in 50% of cases only [6, 7].

6.5.1 Site of Implantation The preferred site of implantation of the valve is the superotemporal quadrant as it is covered by the upper lid and safely away from the optic nerve. Inferior placement has been tried, and the IOP control and decrease in requirement for glaucoma medications were found to be similar as with the superior placement [8]. However, the inferior quadrant placement has higher incidence of postoperative complications as the risk of exposure warranting removal, and endophthalmitis is higher. It is also cosmetically unappealing. Therefore it is recommended that the valve be placed in the inferior quadrant only if there is a contraindication to its placement in the superior quadrant.

6.5.2 Hypertensive Phase A short-lived hypotensive phase may be seen after the surgery which lasts up to 10 days after which a hypertensive phase is common. It may occur in the first month due to the congestion of the bleb wall around the plate. As the congestion decreases and the capsule becomes less dense, the IOP may stabilise [9]. Since AGV is a valved device, the aqueous shunts soon after surgery, the various mediators may trigger the inflammatory reaction. The silicone material of the device may also be responsible for the inflammation

due to lower rigidity and micro movement of the plate [10]. The IOP needs to be monitored, and appropriate anti-glaucoma medications are added to manage the hypertensive phase. In a retrospective study by Ayyala et  al. [11], 82% cases had a hypertensive phase which peaked at 1 month and stabilised at 6 months. One-third of the patients in hypertensive phase required a secondary surgery for control. A study evaluated the use of fixed-dose combination of timolol and dorzolamide when the IOP was more than 10 mmHg, and it was found to be better than a stepped approach in terms of IOP reduction and hypertensive phase frequency [12].

6.5.3 A  djunctive Antifibrotics: MMC and 5-FU Costa et al. [13] compared the short and intermediate rates of success of AGV implantation with MMC.  Their study did not find any significant difference between the eyes with and without MMC. Similar finding reported by Kurnaz et al. [14] documented MMC to be safe and effective but not found to improve the chances of surgical success. Three cases of tube exposure in the MMC group were noted. In another study the patients received intraoperative MMC and postoperative 5-FU, and good IOP control was achieved at 6 years of follow-up [15]. In children

Fig. 7.3  Slit lamp picture showing the pars plana tube seen behind the iris in aphakic eye

41

4. Priming the valve A 27 gauge cannula on a syringe filled with BSS is inserted into the lumen of the tube, and BSS is injected till it flows out through the valve plate. Care should be taken to avoid excessive force during the injection as it may damage the valve mechanism. 5. Insertion and suturing of the plate Two 9-0 nylon/8-0 or 7-0 Vicryl sutures are preplaced onto the eyelets in the anterior portion of the AGV plate and tied. The plate is then gently inserted, while hugging the sclera with the plate, such that the anterior edge of the plate is 8–9  mm away from the limbus. Once in position, the preplaced sutures tied to the eyelets are anchored to the sclera and sutured. 6. Entry into the eye and insertion of the tube The pars plana clip is pulled back to an appropriate length such that it lies over the pars plana region. The tube is trimmed such that it is at least 5 mm length into the eye. A 23 gauge needle can be used to make the entry into the pars plana 3.5 mm from the limbus. The entry should be perpendicular to the sclera with the tip direction toward the center of the eye. A separate irrigating port can be used to prevent collapse of the eye. The tube is then inserted into the pars plana entry. The clip is sutured to the sclera with 9-0 nylon or 7-0 Vicryl sutures (Fig. 7.4). 7. Scleral patch graft: The pars plana clip and the tube should be covered either with donor sclera or preserved pericardium patch. This prevents exposure of the tube/clip. 8. Conjunctival closure: Meticulous conjunctival suturing with interrupted stiches using 8-0 or 7-0 Vicryl is recommended. Mattress sutures are placed at the limbus to prevent exposure of the patch graft. 9. At the end of the surgery, the tube should be visualized by indentation from the scleral side, either through the operating microscope or by indirect ophthalmoscopy.

G. J. Murthy et al.

42

a

b

Fig. 7.4 (a, b) Anterior segment photograph after pars plana AGV implantation

7.6

Variations in Surgical Technique

1. When combining the procedure with pars plana vitrectomy, the supero-temporal port of the vitrectomy itself can be used to insert the tube, especially when micro-incision ­vitrectomy surgery techniques using 23 gauge vitrectomy are used. The plate can be sutured prior to commencement of the vitrectomy, and the tube insertion can be done last, after the vitrectomy is completed. The pars plana infusion is left in place till the end of the surgery and removed only after the tube has been inserted and the conjunctiva has been sutured (Fig. 7.5). 2. A conventional AGV designed for anterior implantation can also be used for pars plana implantation. In some eyes with scarred conjunctiva, there may not be enough place for the

Fig. 7.5  Anterior segment photo showing massive choroidal hemorrhage with choroidal detachment visualized behind the iris after AGV implantation

clip, and increased risk of exposure exists. In such eyes a conventional tube can be used. One should make sure that while inserting the tube into the pars plana, the tube does not acutely

7  Pars Plana Ahmed Glaucoma Valve: Surgical Technique

43

Fig. 7.6  B scan of choroidal effusion occuring post operatively 1 day after AGV implantation

turn and get kinked. Adequate length of the tube should be left intraocularly, so that accidental retraction does not take place. The tube should also be externally anchored to the sclera with a figure-of-eight suture. The plate should also be firmly anchored on the sclera to prevent anterior or posterior migration (Fig. 7.6). 3. In some eyes (aphakic or pseudophakic), the insertion of the tube could be into the ciliary sulcus. The valve used here, could be either FP 7 or FP 8, which is meant for anterior chamber insertion. This type of insertion is preferred especially in eyes post keratoplasty, as the tube is well away from the corneal endothelium.

7.7

Special Situations

Posterior/pars plana relocation of anteriorly placed valve: In situations where there is anterior tube exposure near the limbus, an existing AGV tube can be removed from the AC and reinserted

into the pars plana, without disturbing the posterior part of the tube or plate. The Tenon’s capsule is thicker posteriorly, and if exposure of the tube is anterior, close to the limbus, repositioning the tube into the pars plana can be an option. This is preferable in eyes where the conjunctiva is scarred due to previous surgeries. Progressive endothelial call loss is a complication of AGV implantation into the AC.  Various factors could contribute to this including intermittent contact between the tube and endothelium with lid closure while blinking/eye rubbing in children and anteriorly directed tube which could be touching the endothelium. In a vitrectomized eye, shifting the entry of the tube into the pars plana can prevent further loss of endothelial cells.

7.8

Postoperative Management

Postoperatively, topical steroid antibiotic drops are used on a 2 hourly frequency and tapered over a period of 6 weeks. Antiglaucoma medications

G. J. Murthy et al.

44

are stopped. Topical mydriatic cycloplegic like atropine 1% is used to stabilize the blood ocular barrier and also prevent the occurrence of aqueous misdirection.

7.9

Complications

1. Immediate postoperative (a) Choroidal effusion and delayed suprachoroidal hemorrhage • When high IOP is suddenly reduced especially in single-chamber, vitrectomized aphakic eyes, choroidal effusion results. In an elderly patient, or in the presence of predisposing factors, huge choroidal effusion can lead to stretching of the vortex veins and sudden bleeding into the suprachoroidal space, leading to delayed suprachoroidal hemorrhage. Choroidal effusions which are small can be conservatively managed with topical and if necessary systemic steroids, and if non-­resolving, may require drainage. Delayed suprachoroidal hemorrhage is a devastating complication, and after initial conservative management allowing time for the blood clot to lyse, drainage of the choroidal hemorrhage is undertaken. In eyes with preexisting retinal pathologies, occurrence of these complications may also affect the final outcome of vision and IOP control. (b) Blockage of tube with remaining cuff of vitreous • If the tube length is small, in some instances, the peripheral cuff of vitreous which remains could block the opening of the tube, thereby preventing aqueous drainage. Ensuring adequate length of the tube intraocularly (5–6 mm), and ensuring that complete vitrectomy has been done, will prevent this complication. 2. Intermediate and late complications (a) Retraction of the tube: Posterior migration of the plate, postoperatively, could

lead to the tube retracting and could result in failure of aqueous drainage. This can be diagnosed by ultrasound biomicroscopy of the tube area. Retraction is less likely to occur with the presence of the pars plana clip. (b) Tube/pars plana clip exposure: In previously operated eyes, the conjunctival healing may be compromised and may result in tube exposure. Also, in some eyes where the scleral/pericardial patch graft melts postoperatively, progressive rubbing of the conjunctiva by lid movement may result in tube exposure. Tube exposure, if left untreated, can lead to endophthalmitis with devastating consequences. (c) Conjunctival fibrosis around tube plate which results in decreased filtration and elevation of IOP.

7.10 Literature Review Various studies have established the efficacy of pars plana implantation of AGV in eyes with glaucoma, which have undergone pars plana vitrectomy. All studies demonstrate good IOP control but have a percentage of patients requiring subsequent explantation of the valve due to exposure and other complications. In a long-term study, by Mazinani et al., with a mean follow-up of 23.6 months, 27 eyes showed good control of IOP from a pre-op mean of 30.2 mmHg to 13 mmHg postoperatively after a follow-up of 36 months. However, five eyes required explantation of the valve for various reasons [1]. Similar results have been reported in other studies too [2–5]. Comparison of pars plana vs anterior chamber implantation has also shown similar IOP control in refractory glaucoma eyes. Maris et  al. compared the clinical outcomes of posterior segment vs. anterior chamber implantation of AGV and found similar post-op IOP reduction, success rates, postoperative medications, and similar Kaplan-Meier survival curve analysis. There were more instances of early postoperative flat AC in the anterior group than the posterior group (P = 0.01) [6].

7  Pars Plana Ahmed Glaucoma Valve: Surgical Technique

The pars plana clip in the device has also been shown to be effective; however there are studies which demonstrate that implantation of the AGV device without the clip into the pars plana can also be effective [7, 8]. Pars plana valve implantation has been shown to be particularly more effective in particular in eyes with post-penetrating keratoplasty, neovascular glaucoma, and refractory glaucomas associated with diabetic retinopathy requiring vitrectomy and glaucoma surgery. Various studies have shown that pars plana implantation of AGV may be preferred in post-­ penetrating keratoplasty eyes, as it may have lower level of endothelial cell damage while maintaining similar level of IOP control [9, 10]. Graft decompensation, however, remains a possibility in the postoperative period, and this may reflect the associated ocular morbidity and clinical complexity in these eyes [11]. Pars plana AGV either as a combined procedure with pars plana vitrectomy or as a procedure post vitrectomy has been shown to be effective in the management of neovascular glaucoma [12]. It has also been shown to be effective as a combined procedure along with pars plana vitrectomy in eyes with vitreoretinal comorbidities and glaucoma [13]. In eyes after silicone oil endotamponade, AGV can control the IOP in the majority of eyes. However, the presence of silicone oil is associated with increased risk of surgical failure in eyes treated with the AGV [14]. Silicone oil has also been shown to migrate into the subconjunctival space and orbit, in such eyes [15]. Blocked tubes in the pars plana have been managed by flushing the tube ab interno or by injecting tissue plasminogen activator intravitreally [16, 17].

References 1. Mazinani B, Schwarzer H, Willkomm A, Weinberger A, Plange N, Walter P, Rössler G.  Ahmed glaucoma valve via pars plana access. Long-term results of implantation for therapy refractive glaucoma. Ophthalmologe. 2013;110(6):537–42.

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2. Dada T, Bhartiya S, Vanathi M, Panda A.  Pars plana Ahmed glaucoma valve implantation with triamcinolone-­assisted vitrectomy in refractory glaucomas. Indian J Ophthalmol. 2010;58(5):440–2. 3. Adachi H, Takahashi H, Shoji T, Okazaki K, Hayashi K, Chihara E.  Clinical study of the pars plana Ahmed glaucoma valve implant in refractory glaucoma patients. Nippon Ganka Gakkai Zasshi. 2008;112(6):511–8. 4. Suárez-Fernández MJ, Gutiérrez-Díaz E, Julve San Martín A, Fernández-Reyes MF, Mencía-Gutiérrez E. Simultaneous pars plana vitrectomy and glaucoma drainage device implant. Arch Soc Esp Oftalmol. 2010;85(3):97–102. 5. Lee JY, Sung KR, Tchah HW, Yoon YH, Kim JG, Kim MJ, Kim JY, Yun SC, Lee JY. Clinical outcomes after combined Ahmed glaucoma valve implantation and penetrating keratoplasty or pars plana vitrectomy. Korean J Ophthalmol. 2012;26(6):432–7. 6. Maris PJ Jr, Tsai JC, Khatib N, Bansal R, Al-Aswad LA.  Clinical outcomes of Ahmed Glaucoma valve in posterior segment versus anterior chamber. J Glaucoma. 2013;22(3):183–9. 7. Diaz-Llopis M, Salom D, García-Delpech S, Udaondo P, Millan JM, Arevalo JF. Efficacy and safety of the pars plana clip in the Ahmed valve device inserted via the pars plana in patients with refractory glaucoma. Clin Ophthalmol. 2010;4:411–6. 8. Wallsh JO, Gallemore RP, Taban M, Hu C, Sharareh B. Pars plana Ahmed valve and vitrectomy in patients with glaucoma associated with posterior segment disease. Retina. 2013;33(10):2059–68. 9. Seo JW, Lee JY, Nam DH, Lee DY.  Comparison of the changes in corneal endothelial cells after pars plana and anterior chamber Ahmed valve implant. J Ophthalmol. 2015;2015:486832. 10. Parihar JK, Jain VK, Kaushik J, Mishra A. Pars Plana-­ modified versus conventional Ahmed glaucoma valve in patients undergoing penetrating keratoplasty: a prospective comparative randomized study. Curr Eye Res. 2016:1–7. 11. Lieberman RA, Maris PJ Jr, Monroe HM, Al-Aswad LA, Bansal R, Lopez R, Florakis GJ.  Corneal graft survival and intraocular pressure control in coexisting penetrating keratoplasty and pars plana Ahmed Glaucoma Valves. Cornea. 2012;31(4):350–8. 12. Faghihi H, Hajizadeh F, Mohammadi SF, Kadkhoda A, Peyman GA, Riazi-Esfahani M. Pars plana Ahmed valve implant and vitrectomy in the management of neovascular glaucoma. Ophthalmic Surg Lasers Imaging. 2007;38(4):292–300. 13. Wallsh JO, Gallemore RP, Taban M, Hu C, Sharareh B. Pars plana Ahmed valve and vitrectomy in patients with glaucoma associated with posterior segment disease. Retina. 2013;33(10):2059–68. 14. Ishida K, Ahmed II, Netland PA.  Ahmed glau coma valve surgical outcomes in eyes with and without silicone oil endotamponade. J Glaucoma. 2009;18(4):325–30.

46 15. Nazemi PP, Chong LP, Varma R, Burnstine MA. Migration of intraocular silicone oil into the subconjunctival space and orbit through an Ahmed glaucoma valve. Am J Ophthalmol. 2001;132(6):929–31. 16. Tsui I, Airiani S, Wen A, El-Sawy T, Fine HF, Maris PJ Jr. Intravitreal injection of tissue plasminogen acti-

G. J. Murthy et al. vator as treatment for an occluded pars plana glaucoma tube. Clin Ophthalmol. 2009;3:91–3.. Epub 2009 Jun 2 17. Odrich S, Wald K, Sperber L. Ab interno management of blocked Ahmed valve in the posterior segment. Glaucoma. 2013;22(5):e9–10.

8

Surgical Technique for Baerveldt Glaucoma Devices Gurjeet Jutley and Laura Crawley

Aims of this chapter: • • • • • • • •

When to consider a drainage device Types available Latest evidence Surgical steps Common pitfalls Complications Summary Also refer to the surgical steps videos, with accompanying commentary

Glaucoma management has entered an exciting era; with many ophthalmologists enthused from the plethora of interventions, we can offer to both delay and circumvent irreversible sight loss that otherwise would be inevitable from this devastating condition. In the United Kingdom, the healthcare system is entering an era of austerity, and as such primary prevention with community follow-up is critical. Newer interventions such as earlier diagnosis through the “detecting apoptotic retinal cells” systems, greater patient ownership of their condition via home tonometry, Electronic Supplementary Material  The online version of this chapter (https://doi.org/10.1007/978-981-13-57732_8) contains supplementary material, which is available to authorized users. G. Jutley (*) Oxford University Hospital, Oxford, UK L. Crawley Imperial College London, London, UK © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_8

optometrist-led care from “Google DeepMind” optical coherence tomography and better medical therapy from an explosion of topical neuromodulatory agents can only be the future of glaucoma [1], affording our patients the best possible opportunity to preserve retinal ganglion cells. Irrespective of this, we know a subset of patients will have accelerated disease, and as such surgical intervention is crucial. It is the 50th anniversary of the humble trabeculectomy, and along the way important technique modification has ensured it is an excellent surgical option, including the advent of the safe surgical technique with releasable sutures and the use of antimitotic agents. So if this is the case, what need is there for glaucoma drainage devices (GDD)? Well in those situations where progressive disease is noted despite optimised medical therapy and a trabeculectomy has either failed or is likely to fail, a GDD would be an excellent option. The following prompt consideration of the use of GDDs: • • • • • • • • •

Neovascular glaucoma Iridocorneal endothelial (ICE) syndrome Traumatic glaucoma Uveitic glaucoma Failed trabeculectomy Epithelial downgrowth Refractory infantile glaucoma Aphakic glaucoma Glaucoma in the presence of a penetrating keratectomy or previous pars plana vitrectomy 47

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8.1  Types of GDD The basic design of all GDD is the same with a silicone tube connecting the anterior chamber (or vitreous cavity in the case of pars plana tubes) to the plate, anchored in the subconjunctival space. The design is desirable since the actual tube prevents adherence of fibroblasts, whilst the equatorial explant stimulates a foreign body reaction, thus giving rise to capsule formation, constituting the hypertensive phase at 6  weeks. The actual capsule has a passive function, enabling the egress of aqueous fluid through to the subconjunctival space. It will certainly limit the filtration rate, and at the height of the hypertensive phase, the intra-ocular tension often increases, necessitating the removal of the Supramid suture occluding the lumen of the GDD. The various tubes are subdivided by: • The presence or absence of a flow valve. • Size and shape of the external components. Valved GDD’s with set resistance: • Krupin • Ahmed –– The silicone tube is connected to a silicone sheet valve which is placed in the 180 mm2 polypropylene body. –– Two thin silicone elastomer membranes create a venturi chamber. –– A pressure differential across the valve gives it opening pressure of 7–8 mmHg. –– The inlet cross-section of the chamber is wider than the outlet (Bernoulli principle), with the resultant pressure differential enabling the valve to remain open even Fig. 8.1  Various BVT available, with the variability seen in the size of the plate

with a small pressure differential between the AC and the bleb. The GDDs without resistance valves are: • Molteno –– Newer designs implemented in clinical practice since 1973. –– Long silicone tube approximately 10 mm. • Baerveldt (BVT) The BVT is a non-valved silicone tube device, with a large pliable silicone plate, available in 250, 350 or 500 mm2 [2] (Fig. 8.1).

8.2  Why Use BVT Over the Others Available? The Ahmed versus Baerveldt study was an international, multicentre RCT of 238 patients with high-risk glaucoma [3, 4]. The patients may or may not have had previous interventions, with mean IOP of 31.4 ± 10.8 mmHg. The 3-year data revealed: • The cumulative probability of failure was higher in the Ahmed group. –– 51% versus 34%, p = 0.03. • Trend towards lower IOP in the BVT group. –– 14.4 ± 5.1 mmHg versus 15.7 ± 4.8 mmHg, p = 0.09. The results of this study were very similar to the eminent ABC study [3–8]. An interesting theory is that since the BVT is occluded with the Supramid suture [9] until a bleb forms around the plate (approximately after 6 weeks), it is not exposed to aqueous in the early post-operative period. It is

8  Surgical Technique for Baerveldt Glaucoma Devices

49

postulated that that aqueous in this period will result in bleb remodelling, due to pro-­inflammatory mediators. Conversely, this aqueous exposure in the Ahmed valve will lead to the requirement of glaucoma medications in the long term [10].

should be interpreted accounting for this. One of the failure criteria was IOP less than 5  mmHg. However, the visual acuity was not stated for these patients: it is absolutely plausible for the pressure to be in the “hypotony” range, but as long as the acuity is preserved, these should not be deemed as unsuccessful. The MMC was used for 4  min, which is may be longer than used by most clinicians. This could explain the higher rates of hypotony. Only BVT 350 is used, and hence the results cannot be extrapolated to other tubes. Non-standardized surgical techniques. • Primary TVT study [13, 14]: –– This study is more powerful as all eyes enrolled into the study had no previous surgical interventions. –– The results are eagerly awaited to be published. –– The preliminary first-year data presented at the American Academy of Ophthalmology in October 2016 was hugely encouraging with: –– Failure rates: Trab = 8%. Tube = 20%. –– Complete success: Trab = 59%. Tube = 14%.

8.3  Latest Evidence: Tube or Not to Tube? • Should you do trabeculectomy or proceed directly to GDD? • Trab Versus Tube (TVT study) [11, 12]: –– Multisite, RCT from the USA. –– Cohort included patients 18–85  years of age who have undergone: Previous trabeculectomy. Cataract extraction. –– 212 eyes of 212 patients: 107 in the BVT 350. 105  in the trabeculectomy group (with mitomycin mg/ml used for 4 min). –– Mean IOP at 1 year was similar: 12.4 ± 3.9 mmHg (mean +/-SD) in the tube group. 12.7 ± 5.8  mmHg in the trabeculectomy group (p = 0.73). –– However, the following favoured the use of tube: The cumulative probabilities of failure during the first year of follow-up were 3.9% in the tube group and 13.5% in the trabeculectomy group (p = 0.017). Postoperative complications developed in 36 patients (34%) in the tube group and 60 patients (57%) in the trabeculectomy group during the first year of follow-up (p = 0.001). –– At 5 years, the Kaplan-Meier survival analyses revealed the cumulative probability of failure as: Tube = 29.8%. Trab = 46.9%. –– These results should be interpreted with utmost caution, due to the justifiable criticism of the study: The patients already had previous interventions. It is essentially assessing redo trabeculectomy versus tube and as such

8.4  Technique Our experience has taught us that the pre-­ operative consent, rapport and relationship with the patient are critical to ensure that a properly treated patient is also a happy patient. Important aspects to cover: • Frequent follow-up and drop administration in the immediate post-operative period. • The likelihood of going back to theatre to remove the Supramid suture. • The likelihood of supplementary topical anti-­ hypotensive agents.

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• Complications including: –– Erosion –– Corneal decompensation –– Diplopia –– Sensation of an object in the supero-­ temporal quadrant –– Hypotony –– Choroidal detachments –– Change in refraction –– Acceleration in cataract formation, if the patient is phakic

G. Jutley and L. Crawley

The BVT will often necessitate a general anaesthetic, predominantly as we sling the lateral and superior recti muscle, which stimulates the oculocardiac reflex. Those patients unable to tolerate a general anaesthetic could have an Ahmed valved tube or BVT-250. Consider the following flow diagram, containing surgical stills and tips:

Corneal traction suture: ensure depth is adequate to prevent cheese-wiring

One to two-quadrant, forniceal peritomy. Do a relieving incision laterally, enabling ease of slinging LR

Muscles slung: assistance help to spread muscles can be invaluable.

8  Surgical Technique for Baerveldt Glaucoma Devices

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Plate fixation should be10 mm behind the limbus to ensure reduced contact with the upper lid and risk of exposure

The implant should be secured to the outer sclera: it needs to be anchored for 2 weeks whilst the capsule forms. Securing the plate is crucial to prevent tube instability in the AC with saccades

A tunnel tract is made with a 25 gauge needle, with a tube fed into the AC through this using tube holding forceps.

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Tube fixation achieved using box suture. Increasingly we are using two (one adjacent to plate and other to AC entry).

Patch graft to cover the anterior 5 mm of the tube to prevent exposure & erosion. Our preference is tutoplast (pericardium). Donor sclera or cornea are other options.

Conjunctival closure is augmented with tissue glue where available.

8  Surgical Technique for Baerveldt Glaucoma Devices

53 Anterior aperture

Anterior chamber Tube Posterior aperture

Securing suture holes

Tube plate Superior rectus

8.5  Common Pitfalls and Solutions in Our Experience

• Muscles –– We advocate slinging both the LR and SR, thus reducing the risk of post-operative • Patient selection restrictive myopathy. –– Ensure patients are motivated and physi- • Fixing the plate cally able to administer drops and attend –– Blunt dissection is the key here. If you find frequent follow-up in the acute post-­ the plate is migrating forwards if you operative period. release it when you have placed it in the • Prepare the tube prior to surgery starting sub-Tenon’s space, clearly you have not –– An excellent tip is to: dissected back enough. Bring out the plate Feed the Supramid into the lumen of the and complete your dissection. tube prior to starting the surgery. • Cutting the tube to size Preplace the 10.0 nylon to the superior hole –– The beginning of the surgery commences of the plate, enabling the next bite to be with a traction suture to pull the eye infero-­ into the sclera, ready to be tied. nasally. When adjusting the tube length, • Conjunctiva bring the eye back to primary position, and –– Ensure the history of previous surgery is cut the tube flush to ensure an entry into the elicited. Previous vitreoretinal surgery or AC. This can be trimmed later if originally conjunctival disturbing procedures affects it is too long. the initial dissection. The conjunctiva will –– In fact, cutting it longer is desirable as the be friable and prone to button-holes: knowadjustments can be made sequentially, ing in advance can allow both sufficient ensuring the length is not too short in the time and adjuncts (such as amnion grafts) first instance. to be available.

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• Paracentesis and sclerostomy –– Using viscoelastic in the AC helps to stabilise the AC prior to sclerostomy. –– Injecting viscoelastic through the entry tunnel can ease tube insertion and help the tube glide seamlessly into the AC. –– Occasionally the tube doesn’t fit into the AC: please check the tract is not directed superiorly so the tube is abutting the Descemet’s membrane. –– Use the open-toothed forceps to go through the tract, and manipulate with the smooth shaft to loosen the tract. • Box sutures to fix tube –– Do two: one at the entry of tube at sclerostomy site and other further distal towards the plate. –– Ensures the tube will not dislodge. –– Some surgeons will advocate Vicryl tie around the tube to pinch the edges and reduce the initial flow whilst the capsule is maturing. • Tuck the loose end of the Supramid into the inferior conjunctival pocket –– This can be placed under or over the LR. –– A tip is to crush the end, compressing it with a Castroviejo needle holder. This ensures the end doesn’t have a propensity to poke up outside the conjunctiva, potentially irritating the patient or eroding through. • Tutoplast cover and conjunctival closure –– Adequate suturing with 10/0 nylon or tissue glue can be used to ensure closure. With tissue glue, separating it into thick and thin components ensures greater control. The conjunctival closure is augmented with 10.0 nylon closure, with a variety of continuous and mattress techniques adopted.

8.6  Complications • Hypotony –– The aetiology of which is important to elicit: Over-filtration Ciliary body shut down can be treated by increasing the frequency of steroid drops alongside atropine drops. There may be drainage adjacent to the tube entry point if the sclerostomy was too large (hence importance of using 22-gauge needle). Injecting Healon into the eye and assessing whether it is retained in the AC will be the ultimate diagnostic test for this. Ultimately a revision may be necessary. • Choroidal effusions • Suprachoroidal haemorrhage –– The presentation is typically with sudden excruciating pain with increased IOP in the operated eye either during the operation or in the postoperative period. –– Clinical signs include a shallow AC, increased IOP, and choroidal elevations that appear darker than choroidal effusions. –– B-mode ultrasonography is helpful in making this diagnosis. –– Management includes: Supportive therapy Topical and oral steroids Topical and oral ocular hypotensives Cycloplegic agents Analgesia –– Indications for drainage include: Excruciating pain Involvement of the macula by the haemorrhage Kissing choroidals Corneal-lenticular touch

8  Surgical Technique for Baerveldt Glaucoma Devices

• Blockage of tube –– This may necessitate YAG laser (using an Abraham’s iridotomy lens) to the end of the tube, typically three/four shots at 1  mJ.  Lasering the tube opening causes a shock wave to propagate up the tube and dislodge any debris. Alternatively, it may need to be formally flushed in theatre with balanced salt solution. • Aqueous misdirection –– Can occur months post-operatively • Corneal decompensation [15] –– The incidence is 10–20% irrespective of the GDD used. –– The possible aetiologies include: Physical endothelial touch, necessitating repositioning. Cytokine-mediated damage, from low-­ grade inflammation. • Tube erosion –– Particularly in multi-systemic inflammatory conditions. –– For example, we recently managed a patient with systemic sclerosis with recurrent conjunctival erosion following a Baerveldt 350 [16]. We managed this patient by harvesting the capsule over the original tube, a double-layered Tutoplast on the scleral bed, and placing a pars plana tube (PPT), the plate of which is distal from the site of the previous necrosis. We postulated the site of the original necrosis was due to tight eyelids and made use of the fact that the plate of the PPT was away from this area.

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• Tube migration, including: –– Extension –– Retraction There is a risk that if the tube is cut too short, it can retract out of the anterior chamber due to post-operative subconjunctival fibrosis. • Strabismus and ptosis • Infection [17]

8.7  Summary A plethora of options for the glaucoma surgeon ensures an impressive armamentarium. In the new dawn of minimally invasive surgery, it is important to reflect on the staple interventions and arguably procedures we have 50-years experience with are still the most effective. We have seen the evidence, indication, technique and common pitfalls of Baerveldt tube surgery. The accompanying video will augment this chapter and ensure you are adequately prepared for this surgery. Remember, adequately consent your patient and ensure careful follow-up to manage to ensure both a happy surgeon and more importantly a happy patient. Acknowledgements  Professor Philip Bloom at Western Eye Hospital for access to his clinical photos.

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References 1. Jutley G, Luk S, Dehabadi M, Cordeiro MF. Management of glaucoma as a neurodegenerative disease. Neurodegen Dis Manag. 2017;7(2):157–72. 2. Lloyd MA, Baerveldt G, Fellenbaum PS, et  al. Intermediate-term results of a randomized clinical trial of the 350 versus the 500 mm2 Baerveldt implant. Ophthalmology. 1994;101:1456–64. 3. Christakis PG, Kalenak JW, Zurakowski D, et  al. The Ahmed Versus Baerveldt Study. Design, baseline characteristics, and intraoperative complications. Ophthalmology. 2011;118:2172–9. 4. Christakis PG, Tsai JC, Zurakowski D, et  al. The Ahmed Versus Baerveldt Study. One-year treatment outcomes. Ophthalmology. 2011;118:2180–9. 5. Barton K, Gedde SJ, Budenz DL, et  al. The Ahmed Baerveldt Comparison Study: methodology, baseline patient characteristics, and intraoperative complications. Ophthalmology. 2011;118:435–42. 6. Barton K, Feuer WJ, Budenz DL, et  al. Three-year outcomes in the Ahmed Baerveldt Comparison (ABC) Study. Ophthalmology. 2014;121(8):1547–57. 7. Budenz DL, Barton K, Feuer WJ, et  al. Treatment outcomes in the Ahmed Baerveldt Comparison Study after one year of follow-up. Ophthalmology. 2011;118:443–52. 8. Christakis PG, Tsai JC, Kalenak JW, et al. The Ahmed Versus Baerveldt Study. Three-year treatment outcomes. Ophthalmology. 2013;120:2232–40. 9. Trible JR, Brown DB.  Occlusive ligature and standardized fenestrations of a Baerveldt tube with and without antimetabolites for early postopera-

G. Jutley and L. Crawley tive intraocular pressure control. Ophthalmology. 1998;105:2243–50. 10. Prata JA Jr, Mermoud A, LaBree L, et al. In vitro and in  vivo flow characteristics of glaucoma drainage implants. Ophthalmology. 1995;102(6):894–904. 11. Gedde SJ, Schiffman JC, Feuer WJ, et al. Three-year follow-up of the Tube Versus Trabeculectomy Study. Am J Ophthalmol. 2009;148:670–84. 12. Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the Tube Versus Trabeculectomy (TVT) Study after five years of follow-up. Am J Ophthalmol. 2012;153:789–803. 13. Gedde S.  Treatment outcomes in the Primary Tube Versus Trabeculectomy (PTVT) study after 1 year of follow-up. Presented at: American Academy of Ophthalmology Annual Meeting; Oct. 14–18, 2016; Chicago. 14. Lim S.  Postoperative complications in the Primary Tube Versus Trabeculectomy (PTVT) study during the first year of follow-up. Presented at: American Academy of Ophthalmology Annual Meeting; Oct. 14–18, 2016; Chicago. 15. Sherwood MB, Smith MF, Driebe WT Jr, et  al. Drainage tube implants in the treatment of glaucoma following penetrating keratoplasty. Ophthalmic Surg. 1993;24(3):185–9. 16. Jutley G, Yang E, Bloom PA.  Surgical management of raised intra-ocular tension in the hostile ocular surface: recurrent tube erosion in a patient with systemic sclerosis. BMC Ophthalmol. 2018;18(Suppl 1):222. 17. Tarbak AAA, Shahwan SA, Jadaan IA, et  al. Endophthalmitis associated with the Ahmed glaucoma valve implant. Br J Ophthalmol. 2005;89:454–8.

9

Molteno Implants: Surgical Technique Parth R. Shah, Ashish Agar, and Colin I. Clement

9.1

Introduction and Literature Review

Molteno implants (Molteno Ophthalmic Limited, Dunedin, New Zealand) were developed by Anthony CB Molteno in the 1960s and were the first glaucoma drainage implants in the world. They comprise a fine-bore silicone tube attached to an injection-moulded polypropylene plate drainage plate. There are now several models of the Molteno implant available, each successive model incorporating changes based on surgical experience and outcomes (Table 9.1). It is impor-

P. R. Shah Prince of Wales Hospital, Randwick, NSW, Australia A. Agar Glaucoma Unit, Prince of Wales Hospital, Sydney, NSW, Australia Glaucoma Unit, Sydney Eye Hospital, Sydney, NSW, Australia Marsden Eye Specialists, Sydney, NSW, Australia Department of Ophthalmology, University of New South Wales, Sydney, NSW, Australia C. I. Clement (*) Glaucoma Unit, Sydney Eye Hospital, Sydney, NSW, Australia Eye Associates, Sydney, NSW, Australia Fairfield Eye Surgery, Sydney, NSW, Australia Discipline of Ophthalmology, The University of Sydney, Sydney, NSW, Australia © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_9

tant to know exactly which model is used as the surgical technique is slightly different for each. All Molteno implants are safe with MRI. Several studies have shown the efficacy of the Molteno implants. Molteno and colleagues compared the outcomes from the largest database of Molteno implants in the Otago Glaucoma Surgery Outcome Study. This included 718 cases of trabeculectomy and 260 cases of Molteno implants over 17 years. Results from single-plate, double-­ plate and Molteno3 glaucoma implants were combined and reported as one group. They concluded that insertion of a Molteno implant provided superior long-term IOP control to trabeculectomy when carried out as a first operation in cases of primary glaucoma [1]. At 5-year follow-up, of those with Molteno implants, 21% were on no hypotensive medications, 64% were on one medication, and 15% required two or more hypotensive medications [1]. A retrospective single-centre case series from Finland found that Molteno3 implants for uncontrolled glaucoma reported a 28% complete success rate (IOP 6–20 mmHg off glaucoma drops) and 50% qualified success rate (IOP 6–20 mmHg on 1 or more glaucoma drops) [2]. The group included patients who had failed previous glaucoma procedures. A case series of Molteno single-­plate implants showed effective long-term IOP lowering when performed as the primary surgical procedure for the management of uveitic glaucoma [3]. The author commented that IOP fell progressively during the first year after the 57

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Table 9.1  Currently available Molteno implant models (modified and used with permission from Professor AT Molteno)

9  Molteno Implants: Surgical Technique

surgery, and the medication was slowly tapered even up to 3 years postoperatively. The Otago Glaucoma Surgery Outcome Study showed that 3-year results for the Molteno3 implant were comparable with the double-plate implant [4]. There have been few direct comparative studies between the most popular Molteno, Ahmed and Baerveldt implants. A Cochrane review of aqueous shunts for glaucoma in 2009 reported that there is no evidence of superiority of one glaucoma tube shunt over another [5]. One study showed that Molteno single-plate implants achieved lower IOP in the long term compared with the Ahmed FP7 valved implant (New World Medical, Inc., Rancho Cucamonga, California, USA), with similar rates of surgical failure [6].

Fig. 9.1 Molteno3 device. From: Molteno AC. Molteno3 Glaucoma Drainage Device Surgical Guide. 2006. Available via: https://www.molteno. com/files/299/file/ Molteno-SurgicalGuide-SG-GDD-0816pdf

Secondary drainage area

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9.2

Device Selection

The plate area necessary for IOP control depends on patient age, glaucoma severity and previous ocular history. In general, the greater the amount of aqueous to be drained and the stronger the patient’s fibrosing response, the greater the area required for drainage [7]. The most recent model, Molteno3, has the following features (Fig. 9.1): • Thin plate profile: 0.4 mm thick • Larger drainage area comparable to the Ahmed implant • Primary and secondary drainage areas • Curved to match the shape of the globe: making it suitable for myopic eyes and in patients with tight orbits • Single quadrant surgery

Primary drainage area

Suture hole

Ridge

Suture hole

Translimbal tube

P. R. Shah et al.

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• Same performance as the earlier model double-­plate implant [4] • Trans-limbal or pars plana insertion • Can be positioned supra-Tenon’s if necessary • Flexible curved plate, slides into place easily • Anterior suture hole position for fast, easy insertion

9.3

Surgical Technique for Insertion of Molteno Glaucoma Implant

9.3.1 List of Surgical Instruments • • • • • • • • • • • • • • • • • • •

• •

Molteno implant Lid speculum Fine-spring scissors Non-toothed forceps for handling conjunctiva 2× Squint hooks 2× Steri-Strips Cautery Fine non-toothed suture tying forceps Fine needle holder 2 ml syringe 3× 23-gauge needle Rycroft cannula 7-0 silk suture 2× (or 8-0 Prolene) 5-0 Vicryl (polyglactin 910) suture 1× (optional) 10-0 nylon suture 2× (or 8-0 Vicryl) 3-0 nylon or Supramid (polyamide) suture Anterior chamber maintainer (optional) 15° super sharp blade In cases where the patient’s own sclera cannot cover the tube, donor sclera, or equivalent tissue such as Tutoplast (Innovative Ophthalmic Products, Inc., Costa Mesa, CA, USA) Balanced salt solution 10 mL Subconjunctival antibiotics and steroid

9.3.2 Step-by-Step Guide to Insertion of Molteno Implant Figure 9.2 summarises the steps involved for the insertion of a Molteno glaucoma implant.

1. Local (sub-Tenon or peribulbar block) or general anaesthesia. 2. Betadine prep and sterile head drape. 3. 7-0 silk superior corneal stay suture (see Fig. 9.3 for location). 4. Limbal conjunctival peritomy to create 4-clock hour fornix-based conjunctival flap. (a) Quadrant selection: in general, the superior temporal quadrant is preferred as surgical exposure is better. •  The inferior quadrants may be used when superior quadrant access is limited. The inferior temporal quadrant is preferred in order to minimise the risk of diplopia in patients with good vision in both eyes. •  In eyes containing silicone oil, the implant can be placed superiorly or inferiorly. Any silicone oil entering the tube drains to the bleb, and silicone oil that rarely blocks the ostium can be cleared with neodymium:YAG laser [7]. (b) A non-toothed forcep and fine-spring scissors are used to make a perilimbal incision through conjunctiva and Tenon’s capsule with radial relieving incisions at each end in order to expose sclera and the rectus muscle insertions in the appropriate quadrant(s). 5. Meticulous bipolar diathermy of episcleral vessels. 6. Exposure of rectus muscles. (a) Suture tying of the recti muscles is widely described however is not necessary in the authors’ opinion. (b) Using blunt dissection, Tenon capsule is dissected posteriorly to expose bare sclera 3  mm posterior to the muscle insertions. 7. Position and secure Molteno implant. (a) The plate is sutured between and slightly beneath recti muscles. The plate is positioned so that it lies symmetrically between the rectus muscles, in order to minimise the risk of post-operative diplopia. (b) A 7-0 silk suture (or 8-0 or 9-0 Prolene) is passed through sclera at the rectus muscle insertion, from below up through

9  Molteno Implants: Surgical Technique

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4-clock hour conjunctival peritomy

Diathermy

Expose recti muscles

Healthy, thick Lamellar scleral flap hinged at limbus

Scleral health

Unhealthy, thin

Position and secure implant

Trim tube to correct length

Absorbable suture ligation * Paracentesis Channel formation: sulcus, AC, pars plana

Insert tube

Relieving incisions * * Optional steps

Conjunctival closure

Fig. 9.2  Flowchart summarising the surgical steps in the insertion of a Molteno implant

Donor sclera graft

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Fig. 9.3  Channel formation into ciliary sulcus using 23Ga needle, 3 mm from limbus

the anterior suture hole in the plate, then return the suture through sclera at the muscle insertion in a posterior to anterior direction (mattress suture). Pull the suture tight and tie a knot. Repeat this suture on the other side of the plate [7]. (c) A 7-0 silk suture is recommended because it is braided, holds well in thin and friable tissues and has a nice suture needle for scleral bites. The advantage of the alternative Prolene is durability with reduced chance of plate migration [7]. 8. Scleral covering. (a) A scleral covering over the length of the tube is important to prevent tube extrusion through the conjunctiva. (b) This can be achieved with the creation of a lamellar scleral flap as for a trabeculectomy. The advantage of this is that it avoids the tenting associated with a donor sclera. The disadvantage is that it results in more anterior insertion of the tube, which may be more likely to erode through sclera. There is also a theoretical risk of posterior erosion of the tube into underlying choroid. (c) If the sclera is thin or unhealthy, as is often the case for patients who are candidates for Molteno tubes, a small piece of donor sclera can be used. This can be cadaveric donor sclera (obtained from local Eye Bank) or pericardium (Tutoplast). Tutoplast has the benefit of a

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long shelf life and therefore easily accessible in cases where urgent surgery is required. 9. Trim tube to desired length. (a) Position the tube across the desired location, conventionally oriented perpendicularly to the limbus in line with the origin of the tube from the plate. Trim the end of the tube 2 mm beyond the limbus at an angle of 45° with the bevel facing forward. Take care not to stretch the tube and preferably leave a margin of 2  mm in addition to the desired length just in case there is inadvertent stretch. Remember a long tube can always be trimmed further, but if cut too short, the tube cannot be lengthened! 10. Intraluminal stent. (a) A 3-0 nylon or 3-0 Supramid (polyamide) suture is used as an intraluminal stent. The suture is positioned such that the intraluminal portion ends prior to the tube entering the eye. The other end is placed under the lateral rectus and into the inferior fornix to facilitate removal at the slit lamp or in theatres. 11. Channel formation and tube insertion. (a) The Molteno tube can be inserted into the sulcus, anterior chamber (AC) or pars plana. (b) An anterior chamber (AC) paracentesis is made using a 15° super sharp blade. This allows for reformation of the chamber once the tube is placed. An AC maintainer can be inserted through the paracentesis (optional step, see Fig. 9.5). (c) The authors prefer a ciliary sulcus location in all pseudophakic eyes to avoid endothelial dysfunction associated with an anterior chamber tube. •  A 23-gauge needle on viscoelastic is passed through the sclera 3  mm from the limbus into the ciliary sulcus in a plane parallel to the iris and intraocular lens (Fig. 9.3). Once the needle is estimated to enter the sulcus, a small volume of viscoelastic is injected to balloon the iris forward and ensure there is a

9  Molteno Implants: Surgical Technique

clear space in which to place the tube. The needle is retracted with a small volume of viscoelastic injected into the scleral tunnel on the way out which allows subsequent tube insertion to pass more readily. •  The tube is trimmed with the aim of having it extend to approximately the pupil margin once positioned within the eye. Unlike anterior chamber tube placement, for sulcus placed tubes, the bevel is cut to face backwards. The tube is guided into the sulcus using suture tying forceps (Fig. 9.4). •  When positioned in the eye, confirm its location within the sulcus with either direct visualisation or by applying alternating anterior and posterior pressure

Fig. 9.4  Insertion of trimmed tube into the ciliary sulcus

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on the site of tube entry and observe how the tube within the eye moves in relation to the iris and intraocular lens. (d) Anterior chamber placement. •   With the anterior chamber formed, a 23-gauge needle is used to fashion an entry point approximately 2 mm distal to the limbus (Fig.  9.5). The needle is inserted downwards and forwards, aiming to emerge from the angle parallel to the iris plane. It is important to ensure it emerges as far as possible equidistant from both the cornea and iris, to reduce the chance of touching either. •  A strong pair of forceps is used to thread the tube through this incision (Fig. 9.6). A small relieving cut can be made with the needle, enlarging only the scleral entry point slightly while preserving the narrower intrascleral portion. This is to reduce the risk of peri-tube aqueous leakage which may cause hypotony post-­operatively. If an AC maintainer is not used, the position of the tube must be checked with the AC reformed as the process of insertion can result in shallow. •  If it still appears too close to either the iris or cornea, then a second alternative entry may need to be made. This will be slightly displaced from the original site and so may require additional tube

Fig. 9.5  Channel formation into the anterior chamber. Note an AC maintainer has been used in this case. Images courtesy of Dr. Jed Lusthaus

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Fig. 9.6  Tube insertion into anterior chamber. Images courtesy of Dr. Jed Lusthaus

Fig. 9.7  Vicryl suture tie being placed around tube for delayed drainage

length, another reason to always trim the tube slightly longer than desired. (e) Pars plana placement requires a full vitrectomy to be performed. The technique is similar, but clearly the angle of insertion will be much more acute. 1 2. Optional steps. (a) Delayed drainage: Vicryl suture tie. •  A 5-0 Vicryl suture tie around the tube is an important step in preventing post-op complications related to early over drainage (Fig. 9.7). It allows time for the ­tissues to heal, resulting in a thin and permeable bleb capsule. •  Using a 2 mL syringe and Rycroft cannula, inject saline up the tube to test that the tube has been completely occluded. Place a second throw to lock the knot

and cut the suture ends 3–4 mm long to prevent the knot untying itself [7]. •  The Vicryl tie dissolves in 3–5 weeks. It was proposed that aqueous begins to drain into primary drainage area; the pressure ridge creates a primary bleb underneath Tenon capsule which acts as the flap in a biological valve, keeping aqueous in the primary area, preventing hypotony [7]. The case series reported by Valimaki did not find a low rate of hypotony with the Molteno3 implant [2]. •  As IOP rises, the flap lifts and aqueous drains into a secondary drainage area where it is absorbed into the surrounding tissues. A large secondary drainage area provides for excellent absorption and higher IOP reduction. •  The ‘biological valve’ is reported to be selfcleaning and resists blockage by inflammatory exudate, blood clot or fibroblast ingrowth, unlike a mechanical valve [7]. •  The Vicryl suture can be omitted when treating urgent cases of acutely raised intraocular pressure where medical management in the immediate postoperative period is not appropriate and significant IOP reduction is required immediately. In addition, it may be omitted in some cases of neovascular glaucoma, silicone oil-­ induced glaucoma and a few cases where inflammatory exudate or blood is present in the eye.

9  Molteno Implants: Surgical Technique

Fig. 9.8  Relieving incisions made into tube using the Vicryl suture needle

Fig. 9.9  Donor scleral graft over tube secured with 10-0 nylon

(b) Relieving incisions (Sherwood slits) can be made in the tube anterior to the Vicryl tie using the suture needle (Fig.  9.8). This assists post-operative IOP control by allowing a small degree of post-­ operative drainage. 13. Scleral suturing. (a) The scleral flap or piece of donor sclera is secured to the underlying sclera using 10-0 nylon or 7-0 silk (Fig. 9.9). 1 4. Conjunctival closure. (a) The conjunctiva is closed using 10-0 nylon or 8-0 Vicryl using episcleral bites at the limbus (Fig. 9.10). (b) It is important to ensure that Tenon’s fascia has not been caught behind the posterior edge of the plate and that it lies freely over the limbus of the eye. If caught, carefully lift and free the tissues [7].

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Fig. 9.10  Conjunctival closure using 8-0 Vicryl suture

Fig. 9.11  Appearance at completion of surgery with tube placement into ciliary sulcus in pseudophakic patient

15. Subconjunctival injection of antibiotics (cefazolin) and steroid (dexamethasone) (Fig. 9.11).

9.4

Variations to Surgical Technique for Different Models

9.4.1 Paediatric Version • In a young patient, position the Molteno glaucoma implant in an anterior position, between the insertions of the extraocular muscles. This reduces the impact of subsequent growth of the globe on the length of Molteno implant tubing in the anterior chamber (AC) and reduces the need for reoperation.

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9.4.2 Double-Plate Implant • Molteno double (twin)-plate implants provide twice the drainage area of an original Molteno single-plate (S1) implant without interfering with the action of the extraocular muscles. • The Molteno double-plate implants are suitable for patients with very severe glaucoma, patients with especially vigorous fibrous tissue response, younger patients with good ciliary body function and patients who have glaucoma associated with uveitis or retinal detachment.

References 1. Molteno AC, et al. Long-term results of primary trabeculectomies and Molteno implants for primary open-angle glaucoma. Arch Ophthalmol. 2011; 129(11):1444–50.

P. R. Shah et al. 2. Valimaki J.  Surgical management of glaucoma with Molteno3 implant. J Glaucoma. 2012;21(1):7–11. 3. Vuori ML. Molteno aqueous shunt as a primary surgical intervention for uveitic glaucoma: long-term results. Acta Ophthalmol. 2010;88(1):33–6. 4. Thompson AM, et  al. Otago glaucoma surgery outcome study: comparative results for the 175-mm2 molteno3 and double-plate molteno implants. JAMA Ophthalmol. 2013;131(2):155–9. 5. Minckler DS, et  al. Aqueous shunts for glaucoma. Cochrane Database Syst Rev. 2006;(2):CD004918. 6. Nassiri N, et  al. Ahmed glaucoma valve and single-­ plate Molteno implants in treatment of refractory glaucoma: a comparative study. Am J Ophthalmol. 2010;149(6):893–902. 7. Thompson AM, Bevin TH, Molteno ACB.  Surgical technique 1 (Molteno) (chapter 98). In: Shaarawy TM, Sherwood MB, Hitchings RA, Crowston JG, editors. Glaucoma. London: Saunders Elsevier; 2009. p. 403–16.

AADI Technique

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Suresh Kumar and Sahil Thakur

10.1 Introduction Aurolab aqueous drainage implant (AADI) has been marketed in India by Aurolab, Madurai, India, since June 2013. AADI is a non-valved device that is useful in refractory glaucomas when other methods to control the intraocular pressure have failed. It is made of permanent implantable grade silicone, a proven material for patient safety [1]. The implant plate surface area is 350  mm2, and it has lateral wings that are designed to be placed under the rectus muscle. It is a 35 mm silicon tube attached to a 13 mm convex radius plate which conforms to the curvature of the globe. It has additional holes to facilitate anchoring of the end plate to the sclera so as to minimise device movement. There are various surgical methods of implanting a glaucoma drainage device which have been elucidated in this chapter.

10.2 Dissection of the Conjunctiva A peripheral clear corneal 6-0 Vicryl or 6-0 Prolene suture to provide traction and exposure of the surgical field (Fig. 10.1). The conjunctival peritomy is started in the supero-temporal quadrant to raise a fornix-based conjunctival flap. The preferred location for the implant is supero-temporal quadrant because of more space available in this area. In case of scarring in this region, the supero-nasal quadrant can be used for implant placement. The inferior quadrants are not preferred because of risk of endophthalmitis. Before making a conjunctival incision, it is preferable to inject around 0.5 ml of 4% xylocaine with adrenalin solution under the conjunctiva that aids both in haemostasis and mechanical separation of the tissue from the sclera. Additionally, most of the eyes requiring

Electronic Supplementary Material  The online version of this chapter (https://doi.org/10.1007/978-981-13-57732_10) contains supplementary material, which is available to authorized users. S. Kumar (*) Department of Ophthalmology, GMCH, Chandigarh, India S. Thakur Department of Ocular Epidemiology, Singapore Eye Research Institute, Singapore, Singapore © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_10

Fig. 10.1  Corneal traction suture and dissection bleb raised using lignocaine 67

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implant surgery may already have scarred conjunctiva that can undergo buttonholing with conventional mechanical dissection; fluid-assisted dissection using xylocaine/BSS can help in avoiding this complication. A 9 to 12 o’clock or 12 to 3 o’clock hour peritomy is done depending on the right or left eye that is to be operated.

10.3 AADI Implant and the Extraocular Muscles After the conjunctival incision, only minimal cautery should be used to secure all bleeders in the area where the implant is to be fixed and the needle track is to be created. Excessive cautery can lead to more scarring and irregular astigmatism later on. Using careful blunt dissection, the bare sclera is then approached between the superior lateral rectus. Adequate posterior dissection with tenotomy scissor will ensure proper placement of the plate of the implant. The muscles are then isolated from the surrounding tissue by a cotton tipped applicator and then hooked using a muscle hook. Surgeons should be careful while isolating these muscles as inadvertent damage to these muscles can later manifest as diplopia or strabismus (Figs. 10.2 and 10.3) [2].

10.4 AADI Preparation The AADI needs to be primed before implantation. The patency of the tube is assessed using a hydrating cannula (28 or 30 gauge) and balanced salt solution (Fig. 10.4). Then the tube is ligated with 6-0/7-0 Vicryl suture around 2–3 mm from

Fig. 10.2  Preparation of supratemporal pocket

Fig. 10.3  Both superior rectus and lateral rectus hooked

Fig. 10.4  AADI patency checked

the attachment of the plate. The tube occlusion can be then tested using methylene blue dye. A hydrating cannula is used to inject the dye, while serrated forceps hold the occluded tube. This confirmation of complete occlusion is vital as a ­partially occluded tube can result in early postoperative hypotony. The implant is then slipped under the rectus muscles so as the wings are well placed behind the muscle insertions. The plate is then anchored using 9-0 nylon sutures to the sclera. An effective way is to use the 9-0 nylon suture and make the needle pass through the sclera out through the hole on the implant on the temporal aspect and then take the same needle through the nasal hole of the implant (without cutting the suture) and out through the sclera. The suture is then cut after assessing the length required to tie secure knots which anchor the plate to the sclera. Ideally the plate needs to be secured about 8 mm away from the limbus. This provides sufficient sclera ahead of the plate which can be subsequently used to anchor the tube or for scleral tunnel preparation. Additionally, it is preferable to put plate anchoring sutures in the horizontal direction to more effectively prevent side to side movement of the implant (Fig. 10.5).

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10.5 Tube Placement Techniques 10.5.1 Scleral Tunnel We avoid using scleral tunnels as they pose additional risk of inadvertent scleral perforation. The scleral tunnel if attempted should start about 3–4  mm in front of the plate and extend about 4 mm short of the limbus. We advise putting an anchoring suture using 9-0 nylon between the plate and the tunnel for additional tube stability. About 1–1.5 mm away from the limbus, a needle (23-gauge) track is made into the anterior chamber (AC). While withdrawing the needle from the sclera, it is advisable to minimally extend the entry of the track in the horizontal direction on both sides with the help of needle to assist easy entry of the tube (Fig. 10.6). Some surgeons prefer to additionally push in a little viscoelastic via this needle track to facilitate easy AC entry. It is advisable to always measure the approximate length of the tube using callipers before cutting the tube. The tip of the tube is cut with bevel-up fashion and is made to insert the tube into the AC. Any inadvertent tube track which is made and not used should be sutured to prevent leak and risk of post-operative endophthalmitis [2]. In case of shallowing of the AC during insertion, a paracentesis using a needle or 15° blade can be made to reform the chamber. The tube is subsequently secured using 9-0 nylon sutures to the sclera. The aim is to prevent micromotion of the tube and subsequent extrusion from the AC. As with Baerveldt-type implants, venting slits can be made if immediate IOP control is required [3]. They are made in the tube close to the limbus and away from the occluding ligature with 1–2 small punctures with a spatulated (10-0 nylon) needle (Figs. 10.7 and 10.8).

Fig. 10.5  Implant fixation suture (8-0 nylon)

Fig. 10.6  Anterior chamber entry with 26G needle

Fig. 10.7  Implant with ligating suture (6-0 vicryl)

10.5.2 Patch Grafts As with Ahmed glaucoma valves, a variety of graft materials can be used to cover the tube [4]. We prefer to use split thickness glycerine-­ preserved human cadaveric scleral patch grafts at Fig. 10.8 Fenestrations in tube proximal to ligation our centre for covering the implant. Fresh scleral suture to aid in early IOP control after surgery

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10.7 AADI in Paediatric Population

Fig. 10.9  Partial-thickness scleral-patch graft sutured on the tube

Kaushik et  al. have successfully demonstrated the use of AADI in patients with paediatric glaucoma. They reported a cumulative success rate of 91.18% at 6 months and 81.7% at 18–24 months. The mean number of topical anti-glaucoma medications decreased from 3.1 ± 0.6 to 1.8 ± 1.3 at 6 months and 1.6 ± 1.1 at 24 months (p 35  mmHg in the first postoperative week, and 28 of these (35%) were being treated with glaucoma medications 6 months after surgery. Seven eyes (19%) required cyclocryotherapy to control the pressure. Patients with preoperative raised 85

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IOP or high IOP during the first postoperative week were more likely to have persistent postPK glaucoma [5]. In other studies, incidence of glaucoma following PKP is reported to be 9–31% in the early postoperative period and 18–35% in the late postoperative period [6, 7].

13.2.1 Risk Factors The risk factors for developing glaucoma after PKP: 1. Preexisting glaucoma 2. Aphakia 3. Anterior segment inflammation 4. Corneal diagnosis (herpes simplex, Fuchs’ dystrophy, ICE, keratitis, PBK, ABK, trauma) 5. Intraocular lens removal 6. Vitrectomy 7. Post-keratoplasty/extracapsular cataract extraction/intraocular lens

13.2.2 Rationale for Using the Ahmed Glaucoma Valve Medical management of PPKPG seems most convenient to the doctor as well as to the patient. However, it is not really the best option in most of the patients who require more than one drug. Beta blockers cause dry eye which is detrimental to the health of ocular surface and may lead to unhealthy epithelium and epithelial defects [8]. Dorzolamide suppresses the endothelial pump function leading to corneal oedema or thicker cornea. Prostaglandins can cause inflammation which leads to an immunogenic response hence may abet graft rejection. Activation of herpes due to prostaglandin use too can lead to graft infection and failure. So far, only alpha agonists have no documented direct deleterious effects. Topical medication can be used for a short duration, but for long term, drugs are not an appropriate choice due to their own side effect and effect of preservative on the ocular surface [9, 10]. Trabeculectomy too is associated with complications leading to graft failure

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as well as making patient unfit for contact lens. The use of antimetabolites has been associated with severe intraocular infections leading to profound visual loss [11]. Hence glaucoma drainage devices (GDDs) may provide a safer alternative. They are composed of a silicone tube attached to a flat plate that is sewn to the sclera. Aqueous flows from the eye through the tube onto the plate to form a sub-­tenon bleb. Early postoperative hypotony is avoided by a valve (as in the Ahmed implant) or through an occluding ligature or stent that dissolves or is removed some 4–6 weeks postoperatively.

13.3 Pre-AGV Patient Workup Many of the risk factors outlined above can be screened preoperatively, with a glaucoma-­ oriented ophthalmic examination. Standard evaluation consists of recording of visual acuity, tear film evaluation, lid closure and detailed slit lamp examination for presence of any anterior segment anomaly or subtle inflammation. Examination of the pupil can give a good idea regarding preexisting glaucoma damage. Tonometry and a pupillary examination can often identify previously unsuspected glaucoma despite cloudy cornea. In presence of clear media, gonioscopy is a must to find out angle closure, peripheral anterior synechiae or abnormal structures. In the patients with a significant proportion of the angle obstructed by anterior synechiae, post-­keratoplasty glaucoma is a certainty, and tube in posterior chamber is a safer alternative. In presence of cloudy or opaque media, anterior chamber angle may be examined with anterior segment optical coherence tomography (OCT) [12] and/or ultrasound biomicroscopy (UBM) to determine the configuration of the anterior chamber angle peripheral synechiae and other structures like lens haptic. It aids the surgeon in planning the site for a glaucoma drainage device (GDD) [9]. The presence of a large afferent pupillary defect is an ominous sign. Visual fields are unreliable in the patient with hazy media and impossible to perform in the presence of opaque media.

13  Glaucoma Drainage Devices (Ahmed Glaucoma Valve) in Penetrating Keratoplasty-Associated…

In evaluating patients with hazy media following trauma, Fuller and Hutton [13] found that flash visual evoked potential (flash VEP) was the single best predictor of postoperative vision, followed by bright flash electroretinogram and ultrasonography. It is practical to take fundus photographs at the first examination in patients with clear media and serially repeat them at least once a year to detect if there is any progression of the glaucomatous optic neuropathy.

13.4 IOP: Measurement IOP in the early postoperative period, when the corneal surface is irregular, can be measured with the tono-pen. It has a small plunger and a disposable cover for aseptic technique. The dynamic contour tonometer (DCT) can be used as it has the advantage of not being dependent on the corneal thickness [14]. If the graft surface is smooth, has an intact epithelium and if regular mires can be obtained, then Goldmann Applanation Tonometer can be used to measure the IOP. Marked corneal astigmatism causes an elliptical fluorescein pattern. To obtain an accurate reading with the Goldmann Applanation Tonometer, the clinician should rotate the prism so that the red mark on the prism holder is set at the least curved meridian of the cornea (along the negative axis). Also, two pressure readings, taken 90° apart, can be averaged. The accuracy of Goldmann Applanation Tonometry is reduced in certain situations, such as corneal oedema, scars, blood staining or any condition that thickens or alters the corneal elasticity [15]. Corneal epithelial oedema and stromal oedema predispose to inaccurately low readings. Pressure measurements taken over a corneal scar will be falsely high. Measuring IOP with Goldmann Applanation Tonometer is standardized for a central corneal thickness (CCT) of 520  μm; thus, overestimation of IOP may occur due to an increase in the corneal thickness. The other practical tonometer is I-Care rebound tonometer which has only 1.8 mm contact and can be used without anaesthesia.

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13.5 Technique Anaesthesia-glaucoma drainage devices are usually implanted under local anaesthesia. Peribulbar block is given using lignocaine and sensorcaine in ratio of 50% each along with 150  units of hyaluronidase. Neither external pressure nor adrenalin is used in the block to avoid ischaemia of optic nerve head in an already compromised optic disc.

13.5.1 Surgical Technique The penetrating keratoplasty is done as per the corneal surgeons’ choice, and the sutures are applied. The glaucoma drainage device is subsequently inserted. Some prefer to fix at the plate before the beginning of the surgery and before the button is removed so as to fix in a firm eye. For the purpose of fixation, a superior rectus bridal suture or corneal traction suture is taken. A fornix-based conjunctival flap is dissected in one quadrant, usually a supero-temporal or infero-­ temporal quadrant. Conjunctival flap is dissected meticulously to avoid button holing, and a deep enough pocket is dissected almost beyond the equator to house the silicone plate. If need be, vertical relaxing cuts may be given in tenon to create space for the plate. The valve is primed using 30-gauze cannula to open the valve mechanism as during storage, the flaps of the valve may have become firmly attached to each other. The plate is then sutured with 9/0 nylon to the sclera, 7–9 mm away from the limbus between superior and lateral rectus. The tube is inserted into the anterior or posterior chamber or from the pars plana depending upon the surgical choice. A side port is made to inject fluid or Healon to keep AC formed and firm all the time. The tube needs to be covered to prevent erosion of the tube. For covering the tube, three methods could be used, a rectangular partial-thickness scleral flap, suture-less partial-thickness scleral tunnel, and donor sclera. Partial-thickness scleral flap technique—In this technique, a partial-thickness limbal-based scleral flap measuring 5 mm × 5 mm is dissected.

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The entry into the anterior chamber is made using 23-gauze needle underneath the partial- thickness flap about 1 mm away from the posterior limbus. The direction is chosen depending upon its location anterior or posterior to the iris. Now, the tube is made straight from its attachment to the plate and measured so that about 2 mm of tube will be in the anterior chamber or posterior chamber and cut on the distal end with a tapering intraocular end. Posterior chamber is the preferred site as it prevents the tube cornea touch which may lead to chronic endothelial loss progressing to corneal decompensation. The tube is fixed to the sclera near the plate using 10/0 nylon suture on spatulated needle. Then, partial-thickness scleral flap is sutured with 10/0 nylon on the top of the tube to cover it completely. The conjunctival flap is stretched to cover the entire area and is sutured from end to end including the partial-thickness bites on the clear cornea with 8/0 vicryl suture. The aim is to prevent any exposure of overlying sclera which may melt if left exposed. A well-­ maintained anterior chamber with a little firm eye is the end point.

13.5.2 Scleral Tunnel Technique [16] In this technique, instead of a scleral flap, a partial-­ thickness scleral tunnel is dissected, which is open at both ends. After fixing the valve with the sclera, the tube is stretched forward to see the location of tube. After that tube is kept away by tucking it in the speculum. Two incisions measuring 2 mm are made parallel to the limbus. The distance from the limbus is kept 1 mm and 7 mm away. With the help of a scleral tunnel blade, these two incisions are connected to each other at approximately half-thickness deep scleral just like in SICS.  Now the tube is shortened for 2  mm length in AC.  It is passed from 7  mm away incision to 1  mm incision and is exteriorized. A 23-gauze needle is then inserted into AC in phakic eyes and PC in aphakic or pseudophakic eyes to create a wound of entry for the tube. Then, the tube is inserted into AC/PC.

13.5.3 Scleral Patch Graft Cover of the Tube The technique is similar to the above, except that no scleral flap or tunnel is made. Tube is covered with a scleral patch graft from the cadaver eye. Suturing is done with 8 or 9/0 nylon, and the conjunctiva is closed. This technique is extremely useful when the sclera is thin and fragile due to multiple surgeries, collagen disorders and thin sclera in children. Scleral cover can also be used on top of the tunnel for thicker tube cover in case following surgery tube exposure is expected.

13.5.4 Pars Plana Tube Insertion Technique The tube can be inserted through the pars plana only in the eyes which have undergone vitrectomy. In case vitrectomy is done in the same sitting, the tube is inserted from the same 23-gauze; MVR port else in previously vitrectomized eyes a fresh port can be made with 23-gauze needle, and the tube is inserted. The remaining tube is covered with donor sclera, and the procedure is completed.

13.6 Postoperative Care Postoperative care is the same as in all the cases of AGV/GDD.  However, anti-corneal graft rejection protocol is started with the use of oral steroids in the dosage of 1  mg/kg. One hourly topical steroids and if required cycloplegics are used with the aim to keep the inflammation and immune status of the eye to the least. The special points which need to be taken care of are tube corneal touch, hypotony and shallow AC, immunogenic graft rejection and dellen formation due to high bleb. Tube corneal touch can lead to chronic endothelial loss leading to graft failure. To prevent tube corneal touch, special care is taken to use the correct direction and placement of the tube. In case it is not so, a revision surgery to reinsert the tube is indicated (Fig. 13.1).

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Ahmed Glaucoma Valve

• Tube in PC • Bleb

Fig. 13.1  Postoperative pictures of the eye with penetrating keratoplasty and AGV. Note the bleb and the tube in posterior chamber. Also shown are the parts of the AGV

Hypotony can lead to endothelial loss and graft failure. To prevent this, wound entry is kept tight fitted. Some Healon may be left in AC if there is hypotony. If shallow AC occurs, prompt measures to correct it by using Healon injection in AC may be done. Corneal graft rejection can be initiated by any surgical or inflammatory insult to the cornea, and AGV is a surgery; hence, we need to take pre-­ emptive steroid cover to prevent it. Following this, a graft needs close watch for rejection. Early signs of graft rejection may be masked due to steroid cover, but meticulous search must be made for Khodadoust line, localized graft oedema and KPs, especially close to sutures or blood vessel. Early detection with aggressive treatment can save the graft from failing. Steroid responders need to be watched carefully as steroid response and hypertensive phase of bleb commence at the same time, and it is

important to manage both. Usually, hypertensive blebs are high and congested, and steroid responders will have less high and less raised blebs [17]. True demarcation is really difficult. If the bleb is high and congested, we can keep the steroids on or can use something like betamethasone along with antiglaucoma medications. If bleb is good, a very mild steroid like fluorometholone may be used with antiglaucoma medication till such time IOP rise persists. Post-penetrating keratoplasty patients usually need some amount of steroid for a very long period of time. To prevent hypertensive phase, it is may be wise to start antiglaucoma medication after 10–15 days even if the IOP is normal. Very high blebs affect corneal wetting and may lead to dellen formation. A high viscosity lubricant can be used to prevent dellen formation. Although GDDs demonstrate an excellent rate of IOP control, the risk of corneal graft

M. Bhadauria

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failure is high and may be even higher than in the eyes undergoing trabeculectomy. The high incidence of graft rejection following AGV is an important matter, and the reported incidence has been between 15% and 41%. Kirkness describes pathogenesis of graft rejection by the presence of a tidal flow of cells in and out of the tube located in the AC leading to a possible contact of aqueous humour with circulating lymphocytes, through the drainage tube, and the tube may also allow the retrograde passage of inflammatory cells into the AC, increasing the risk of graft rejection [18]. The other mode of occurrence, as hypothesized, could be due to an alteration of the blood-ocular barrier caused by the GDD.  Studies show that graft failure is maximum when GDDs are placed post PK [19]. This was attributed to corneal endothelial trauma during GDD implantation which is more relevant to post-PKPG eyes [20].

13.7 Conclusion Success rate following AGV in PKPG is tabled below as published in IJO [21]. The results of authors in the table are compared with IJO study [19, 22, 23]. No. of Authors and year eyes Colemann et al. 16 1995 [24]

Follow-up (months) 9.3

Topouzis et al. 1999 [25]

16

30.5

Romaniuk et al. 2004 [20] Present study (Panda et al., 2010)

17

12

20

6

By the use of GDD, some patients may not require any further treatment, but the number of glaucoma medications is significantly reduced even in those patients who qualify to be successful. Hypertensive phase is seen in nearly 80% of Indian eyes but gets controlled by steroids and antiglaucoma medications. Success rate has been found to be higher when the AGV or GDD is either done before PK or simultaneously [25]. Post PKPG patients are not only prone to graft failure following AGV but also are less successful in terms of IOP control. Many patients who need to undergo PK often have glaucoma either before PK or develop glaucoma following PK.  It is prudent to do a good glaucoma evaluation in all the patients who are likely to undergo PK so that glaucoma can be controlled before PK is done. In case of AGV, success rate in terms of IOP control is more if done before PK; it will be wise to do so as the surgeon can do PK on a quite eye with low pressure. AGV can be done simultaneously if IOP is not likely to be controlled on drugs following PK. If glaucoma develops following PK and AGV is required, it should be done with all the due care to avoid graft rejection or failure. Done properly, it is a good modality for long-term success and reduction of antiglaucoma medications.

Definition of success (mmHg) IOP 20% if preoperative IOP > 22, IOP > 4 for >2 months, no additional glaucoma surgery, no visually devastating complications 6 300 million inhabitants, the yearly investments in glaucoma care are significant and increase with ageing population [6]. It is extremely important for us to understand the economics of glaucoma and to prepare the infrastructure to combat the increasing costs and demand of glaucoma care. We also need to provide our patients with affordable medical and surgical treatments to make the glaucoma management cost-effective. 143

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20.2 Glaucoma in Developing Countries

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The cost of medical management of glaucoma has been increasing over the years. Lam et  al. have explored the trends in glaucoma medication The major population of the world resides in expenditure, and they concluded that the factors developing countries. As per Quigley there are associated with increasing glaucoma medication 12.3 million people in the world who are blind expenditure trends include the increasing use of due to glaucoma, and 70 million people are suf- prostaglandin analogues, changes in insurance fering from glaucoma [1]. As  the  rate of angle-­ coverage, and possibly more aggressive glauclosure glaucoma is higher in the Asian population coma treatment [8]. In the Western world, the and open-angle glaucoma in African population, major cost of treatment is borne by insurance a vast majority of patients with glaucoma reside companies; however in developing countries like in developing countries. India, the cost of therapy is mainly borne by the Lack of awareness of the  disease is also a patient himself. In a study from a tertiary eye care major concern. As glaucoma is a silent disease hospital in India, less than 10% of their patients and is practically symptomless, most patients are got their bills reimbursed by medical insurance detected late. Lack of education and regular eye [4]. Because of self-financing, a lot of newer and check-up also contributes to late detection of generally costlier treatment interventions are not glaucoma. Due to poor awareness, these patients available in the developing world and even when are not willing to use medicines regularly or available have poor acceptance. Very few studies undergo glaucoma interventions. from India have tried to assess the cost of therapy Cost is a major issue in these countries along for glaucoma patients [4]. In fact there are none with poor availability of medications, lack of which have studied the cost-effectiveness of health insurance and extremely poor adherence glaucoma drainage devices in the developing to therapy. Due to all these factors, often surgery world. Most of the available data is from Western is considered as a primary treatment modality in literature. If one understands the finances better, these countries. According to the United Nations one can better utilise the available resources. It is and World Bank, more than 1.3 billion people essential to choose the treatment which is most worldwide live on less than 1 USD per day, and affordable and economically viable for the target most of them reside in developing countries [7]. patient group. Glaucoma surgery compared to cataract surIn developing countries like India, a large gery cannot improve vision but rather may lead to chunk of people belong to the low-income vision threatening complications. Hence it is often group, and for them the affordability of drugs is avoided by ophthalmologists and poorly accepted a major issue. Even trabeculectomy too is often by patients too. As the number of glaucoma sur- not affordable. Hence glaucoma drainage geries is going down, a lot of practising ophthal- devices (GDD), due to their higher cost, remains mologists are not competent in performing a big prohibition for patients and their care reasonably successful trabeculectomies. Lack of providers. experience of surgeons and poor confidence result For glaucoma drainage devices, cost is a major in poor surgical outcome and ultimately result in issue. The surgical time taken in glaucoma sura bad name for the glaucoma surgery. The number gery is more than routine cataract surgery making of trained specialists who can perform glaucoma it less cost-effective (less profitable) for institudrainage device surgery is even fewer. tions. Study done in a tertiary care centre in India Surgical cost is high initially, but once suc- has shown that more than 50% of patients had cessful the cost goes down as there is lesser need income of less than 5000 rupees (80 USD) per of medication and lesser follow-up in the long month; hence affording an Ahmed glaucoma run. However, even in developing countries, the valve  costing nearly 15,000 Indian rupees (260 rate of glaucoma surgeries is low primarily due to USD) is difficult [4]. As per Nayak and group, poor acceptance of trabeculectomy and its unpre- per month expenditure on drugs was between dictability [4]. USD 8.2 and USD 307.09 with an average of

20  Economic Considerations of Glaucoma Drainage Devices

USD 65.6 per month [4]. Acceptance of surgery was poor, and when given as option, only 4% of patients opted for surgery as primary treatment versus lifelong medication. Anand et al. however have noted a much better acceptance of primary surgery after proper counselling [9]. They have shown that 35% of patients accepted early surgery which increased to 65% on proper counselling and educating patients about glaucoma.

20.2.1 How Funding Can Be Improved 1. Government or private health insurance, at a nominal premium, needs to be made popular. Glaucoma shunt surgery too needs to be covered by these policies. 2. Government subsidy: Government may provide subsidy to not-for-profit hospitals performing glaucoma surgery including shunts. Tax rebate on glaucoma shunts too can enhance the popularity of these devices. 3. Corporate social responsibility: Corporates may be requested to sponsor glaucoma shunt surgery in charitable hospitals catering to patients of low-income group.

20.3 Glaucoma Drainage Devices Aqueous shunts or glaucoma drainage devices (GDD) are used as surgical intervention to control IOP (intraocular pressure) in patients with advanced glaucoma with failed standard surgeries like trabeculectomy or in patients with glaucoma subtypes where trabeculectomy is unlikely to succeed [10, 11]. Molteno implant was the first widely used glaucoma drainage device. Newer shunts like Baerveldt contain single plate without a flow-restrictive mechanism, while Ahmed glaucoma valve  contains a flow-restrictive valve to reduce post-operative hypotony [10]. The use of aqueous shunts is increasing. A study of Medicare fee for service data  in the United States reported that the number of aqueous shunt procedures in Medicare  beneficiaries  increased from 2728 procedures in 1995 to 7744 procedures in 2004 (184% increase).

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Concurrently the number of trabeculectomies decreased from 51,690 in 1995 to 24,178 in 2004 (53% decrease) [12].

20.3.1 Indications of Glaucoma Drainage Devices Survey among members of the American Glaucoma Society has noted eight main conditions where shunts have become a primary surgical choice for more than 50% of its members (2008) [13]. The eight major indications of shunts are: 1 . Previously failed trabeculectomy 2. Previous intra- or extracapsular cataract extraction 3. Previous phacoemulsification 4. Post-penetrating keratoplasty 5. Post-scleral buckle 6. Post-pars plana vitrectomy 7. Uveitic glaucoma 8. Neovascular glaucoma Aqueous shunts are currently the standard of care for complicated glaucoma in the United States especially in pseudophakic eye with previous one or more failed trabeculectomies [10]. The long-­ term success is comparable to trabeculectomy; however trabeculectomy may provide lower IOP compared to shunts. The failure rate of shunts is approximately 10% per year which is quite similar to trabeculectomy [14].

20.4 Cost-Efficacy of Treatment Effectiveness describes outcome of a treatment modality in everyday practice, and it is always worse than efficacy which is the outcome of an intervention in an ideal setting like randomised control trial. Unless an intervention is both efficacious and cost-effective, it cannot be clinically useful. Management of glaucoma is getting costlier over time as most glaucoma medications are expensive and there is a trend among practising ophthalmologists to use newer medications which are generally costlier [15].

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20.4.1 Types of Economic Analysis Most economic analysis considers the cost of illness or cost of the condition. It basically analyses the natural history of illness, untreated impact of disease on productivity, overall morbidity as well as total cost of treatment modalities [16]. Cost of illness can be divided into cost of the disease itself or the cost of its intervention. The cost of disease includes: 1. Economic value of disabilities due to loss of productivity/time lost at work 2. Cost of care at home/alternative living facility due to disease 3. Direct cost of family members or social support persons to help the individual with the disease 4. Loss of government tax due to loss of productivity due to illness 5. Years of life lost due to the disease and its financial impact

M. Singh and A. Mitra

drainage devices are not more effective than trabeculectomy if the patient does not have risk factors for increase in conjunctival fibrosis. The Cochrane review of medicines versus surgery for open-angle glaucoma stated that in severe glaucoma (MD  >  10  dB), initial surgery (trabeculectomy) is associated with marginally less visual field loss at 5 years than initial medications [18]. However the study also expressed the view that primary surgery was associated with more local eye symptoms, more incidence of cataract, and reduced visual acuity up to 5 years of follow-up. A more recent Cochrane review on aqueous shunts analysed the effectiveness of glaucoma shunts compared to trabeculectomy [10]. They concluded that it was uncertain whether aqueous shunts were safer or more effective than standard trabeculectomy based on the very low certainty evidence. They however stated that Baerveldt and Molteno implants reduced eye pressure more than the Ahmed shunt and fewer glaucoma medications were needed with the former two.

Cost of treatment intervention includes: 1. The cost of care provider (outpatient and inpatient) 2. Cost of drugs 3. Cost of devices and aids 4. Productivity loss due to adverse effects of treatment and its management 5. Loss of productivity of family members for assisting in treatment related activities

20.5 Benefits of Glaucoma Surgery Various studies have been published highlighting the efficacy of surgery in glaucoma management. The Finnish evidence-based guideline for glaucoma stated that not only did surgical management lower the intraocular pressure (IOP) more than medications and laser treatment but it also resulted in better control of the diurnal variation of IOP [17]. The study also highlighted the fact that early surgical intervention slowed the visual field loss progression more than medical or laser treatment. However, the study also stated that glaucoma

20.6 Cost-Effectiveness of Glaucoma Surgery There is lack of published data comparing cost-­ effectiveness or cost-utility of laser, surgical, or medical treatment. Worldwide with increased number of glaucoma patients, the  number of glaucoma prescriptions have increased and so has the total expenditure on medications. However, there is a  gradual decrease in the rate of glaucoma surgeries [19, 20]. The role of laser procedures (Trabeculoplasty) too has decreased over time [20]. The rate of cataract surgery has been increasing worldwide. There is a possibility that lowering of IOP (1–4 mmHg) by phacoemulsification in glaucoma patients might have a protective role for them. Ainsworth and Jay studied 104 glaucoma patients (newly diagnosed) who received either conventional medical therapy (n = 53) or underwent primary surgery (trabeculectomy) (n  =  51) [21]. The total cost in surgery group was twice than the conventional therapy  group in the first

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year, but the cost steadily decreased in the surgery group over the  next few years due to less or no need of costly glaucoma medications in the surgery group. The total cost in bilateral cases was equal in both groups by 8 years of follow-up [21]. Hence, in the long run, the cost difference in medical versus surgical therapy was not significant. Kaplan first analysed the cost-effectiveness of Baerveldt implant (350 mm2) in comparison with trabeculectomy with mitomycin C and medical management. They observed that glaucoma drainage devices and trabeculectomy both are cost-effective procedures. Quality of life and 5-year cost burden were markedly similar for glaucoma drainage devices and trabeculectomy compared to medical management. Trabeculectomy had substantially lower cost per quality-adjusted life-years (QALY) compared to tube insertion [22].

Florida. It became commercially available in India since June 2013. Kaushik et al. have studied the safety and efficacy of this low-cost glaucoma drainage device (AADI) in patients with refractory childhood glaucoma [23]. They included 34 eyes of 31 patients. The authors have reported a cumulative success of 91.18% at 6 months and 87.7% at 18–24 months. They have concluded that it is a viable low-cost glaucoma drainage device with effectiveness which is comparable to published reports of Baerveldt glaucoma drainage implant and Ahmed glaucoma valve. The long-term efficacy of AADI is yet to be established, but it does offer an affordable therapeutic option for the glaucoma surgeon in India in terms of implant cost alone. Its cost-effectivity with respect to surgical time, multiple interventions, long-term effectiveness and learning curve is yet to be established.

20.7 Implant Costs

20.8 Summary

Ahmed glaucoma valve (AGV, New world Medical Rancho Cucamonga California) at USD 260, the Baerveldt glaucoma drainage  implant (Advanced Medical Optics, Santé Ana California, USA) at USD 750 are simply beyond the reach of majority of those who need it the most. Developing countries like India have a large glaucoma population of which a significant proportion of complicated and refractory glaucoma patients need glaucoma drainage devices but cannot afford these costly implants.

• Worldwide the total number of glaucoma surgeries has gone down, but there is an increasing trend of the use of glaucoma drainage devices. • There is lack of data evaluating cost-­ effectiveness of glaucoma drainage devices, but most available data have found them to be economically viable over a long-term period. • Availability of low-cost glaucoma drainage devices will further enhance the affordability and use of these shunts. • We need more studies, specially from the  developing world, evaluating the cost-­ effectiveness of glaucoma drainage devices in terms of long-term preservation of visual field.

20.7.1 Low-Cost Implants: Aurolab Aqueous Drainage Implant (AADI)

The Aurolab aqueous drainage implant (AADI) has been introduced recently by the Aurolab, the References manufacturing division of Aravind Eye Institute, Madurai, India. It is a low-cost (USD 50) non-­ 1. Quigley H, Broman AT.  The number of people with glaucoma worldwide in 2010 and 2020. Br J valved glaucoma drainage device designed like Ophthalmol. 2006;90:262–7. the Baerveldt glaucoma drainage  implant with 2. Heijl A, Leske MC, Bengtsson B, et  al. Reduction 2 350 mm plate area. of intraocular pressure and glaucoma progression: The device was manufactured in association results from Early Manifests Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268–79. with Bascom Palmer Eye Institute, Miami,

148 3. Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open angle glaucoma. Arch Ophthalmol. 2002;2120(6):714–20. 4. Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the Tube Versus Trabeculectomy (TVT) study after five years of follow-up. Am J Ophthalmol. 2012;153(5):789–803. 5. Gedde SJ, the Tube Versus Trabeculectomy Study Group. Results from the Tube Versus Trabeculectomy Study. Middle East Afr J Ophthalmol. 2009;16(3):107–11. 6. Tuulonen A.  Economic considerations of the diagnosis and management for glaucoma in developed world. Curr Opin Ophthalmol. 2011;22:102–9. 7. Boeteng W.  Economics of surgery worldwide. In: Shaarawy TM, Sherwood MB, editors. Glaucoma, vol. 2. Edinburgh: Saunders Elsevier; 2009. p. 13–6. 8. Lam BL, Zheng D, Davila EP, et al. Trends in glaucoma medication expenditure. Medical expenditure panel survey 2001–2006. Arch Ophthalmol. 2011;129:1345–50. 9. Anand A, Negi S, Khokhar S, et al. Role of early trabeculectomy in primary open angle glaucoma in developing world. Eye. 2007;21:40–5. 10. Tseng VL, Coleman AL, Chang MY, Caprioli J. Aqueous shunts for glaucoma. Cochrane Database Syst Rev. 2017;7:CD004918. 11. American Academy of Ophthalmology Glaucoma Panel. Preferred Practice Pattern Guidelines. Primary open angle glaucoma. San Francisco, CA: American Academy of Ophthalmology; 2010. www.aao.org/ ppp. 12. Ramulu PY, Corcoran KJ, Corcoran SL, Robin AL.  Utilization of various glaucoma surgeries and procedures in medicare beneficiaries from 1995 to 2004. Ophthalmology. 2007;114(12):2265–70.

M. Singh and A. Mitra 13. Desai MA, Gedde SJ, Feuer WJ.  Practice prefer ences for glaucoma surgery: a survey of American Glaucoma Society in 2008. Ophthalmic Surg Lasers Imaging. 2011;42(3):202–8. 14. Minckler DS, Francis BA, Hodapp EA, et  al. Aqueous shunts in glaucoma. A report by American Academy of Ophthalmology. Ophthalmology. 2008;115(6):1089–98. 15. Tuulonen A.  Economics of surgery worldwide. In: Shaarawy TM, Sherwood MB, editors. Glaucoma, vol. 2. Edinburgh: Saunders Elsevier; 2009. p. 3–11. 16. Lee P, Matchar DB. Economics of glaucoma care. In: Shaarawy TM, Sherwood MB, editors. Glaucoma, vol. 1. Edinburgh: Saunders Elsevier; 2009. p. 25–32. 17. Tuulonen A, Airaksinen PJ, Erola E, et al. The Finnish Evidence Based Guideline for glaucoma. Acta Ophthalmol Scand. 2003;81:3–18. 18. Burr J, Azuara-Blanco A, Avenell A.  Medical versus surgical intervention for open angle glaucoma. Cochrane Database Syst Rev. 2005;(2):CD004399. 19. Whittaker KW, Gillow JT, Cunliffe IA. Is the role of trabeculectomy in glaucoma management changing? Eye. 2001;15:449–52. 20. Rachmiel R, Trope GE, Chipman ML, et  al. Laser trabeculoplasty trends with introduction of new medical treatments and selective laser trabeculoplasty. J Glaucoma. 2006;15:306–9. 21. Ainsworth JR, Jay JL. Cost analysis of early trabeculectomy versus conventional management in primary open angle glaucoma. Eye. 1991;5:322–8. 22. Kaplan R, Moraes CGD, Cioffi GA, et al. Comparative cost effectiveness of the Baerveldt implant, Trabeculectomy with mitomycin and medical treatment. JAMA Ophthalmol. 2015;133(5):560–7. 23. Kaushik S, Kataria P, Raj S, et  al. Safety and efficacy of a low cost glaucoma drainage device for refractory childhood glaucoma. Br J Ophthalmol. 2017;101(12):1623–7.

Quality of Life Following Glaucoma Drainage Device Surgery

21

Bernardo de Padua Soares Bezerra, Syril Dorairaj, and Fabio Nishimura Kanadani

21.1 Introduction Understanding the impact of the disease and its treatment on the patient’s quality of life is an important aspect of medical care. Good quality of life is sought after by the vast majority of patients. People value their vision highly, more than physicians realize [1, 2]. Decrease in visual ability has a direct impact in glaucoma patient’s quality of life. Serious consequences of reduced vision include fall injuries with reduced mobility, increased risk of motor vehicle accidents, and decreased ability to perform daily life activities [3]. Avoiding obstacles in dim lighting, reading through a line, adjusting to shifting light conditions, and other tasks that require contrast sensitivity or peripheral vision may become challenging [4]. A patient-centered approach is considered a best practice to assess the efficacy of emergent and established treatments [5–7]. Although there is extensive information on how glaucoma as a

B. de Padua Soares Bezerra (*) Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia S. Dorairaj Mayo Clinic, Jacksonville, FL, USA F. N. Kanadani Instituto de Olhos Ciencias Medicas, Belo Horizonte, Brazil © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_21

disease affects the patient’s daily life, there is lack of information regarding how glaucoma treatment affects one’s quality of life [8–17]. The only multicenter randomized clinical trials (RCT) to this date that report quality of life after treatment intervention are the Collaborative Initial Glaucoma Treatment Study (CIGTS) and the Tube vs. Trabeculectomy study (TVT) [18–20]. While the CIGTS looked at recently diagnosed glaucoma patients, the TVT study included a cohort of patients with a more advanced disease profile and was the only RCT up to date to address glaucoma drainage device and quality of life of patients that had undergone this procedure.

21.2 Assessing Quality of Life Self-reported indicators of quality of life are valuable methods of assessing how illnesses affect people. However factors as patient’s emotions, personalities, and psychological considerations influence subjective perceptions of the effects of disease and adequacy of vision [21, 22]. Patients are primarily interested in how well they are able to function: read signs at a distance, drive, recognize people, find things in the supermarket, and other daily activities [23]. We better comprehend how the disease affects patient’s daily lives through generic health-­related quality-of-life (QoL) instruments 149

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and vision-specific and also glaucoma-specific instruments [23]. There are three distinct approaches to measuring the impact of glaucoma on individuals’ lives [24]: 1. Clinical measures: visual acuity, contrast sensitivity, and visual field 2. Self-reported measurements of subjective well-being 3. Performance-based assessments of the ability to carry out daily activities A myriad of tests are used to assess quality of life, and we summarize the most used and validated ones.

21.3 T  he National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25) The NEI VFQ-25 is widely used. It stands as a benchmark for comparison with other specialized glaucoma QoL instruments [4], developed as a mechanism to evaluate vision problems though not focused on a specific condition and designed as a shorter version (compared to the 51- and 96-item versions) but yet reliable, and validated form of capturing visual problems on physical functioning, emotional well-being, and social functioning. Disadvantages are that it is a test designed for advanced pathology and might not be accurate for early-stage disease [25]. Compared to the normal control subjects, glaucoma patients scored significantly lower, including difficulty in driving and role limitations because of poor vision. Significant visual field loss in the better eye correlated with poorer scores [26].

21.3.1 Minimal Important Difference (MID) Minimal important difference (MID) can be defined as the smallest difference in score in the

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domain of interest which patients perceive as beneficial and which would mandate, in the absence of troublesome side effects and excessive cost, a change in the patient’s management [27]. Both the US Food and Drug Administration and the European Medicines Agency recommend the use of MIDs as a method of evaluating effectiveness of new treatments [28].

21.3.2 Visual Activities Questionnaire (VAQ) Visual Activities Questionnaire (VAQ) evaluates patients’ perceptions of their visual function. Patients answer to a five-point scale from “never” to “always” if they had experienced one of the eight subscale symptoms: glare disability, light/dark adaptation, acuity/spatial vision, visual search, visual processing speed, depth perception, color discrimination, and peripheral vision [20]. As it includes a peripheral vision subscale, the VAQ was included in the arsenal of QoL questionnaires used in the CIGTS.  Peripheral vision subscale scores correlated more strongly with visual field measurements, while overall VAQ scores correlated equally well with visual field and visual acuity measurements [20]. The VAQ peripheral vision subscale scores had the strongest association with stratified categories of visual field scores out of all the tests used in the CIGTS [20]. Symptom and Health Problem Checklist has 43 symptoms related to the disease process or side effects of treatment. Symptoms have subscales: visual function, 11 points; local eye, 7 points; systemic, 20 points; and psychological, 5 points. For each symptom patients describe if they have experienced it in the past 7 days, if it was related to the glaucoma treatment (entirely, partially, or not at all), and how bothersome the symptoms were (from “a lot” to “not at all” in a five-point scale) [20]. It is important, however, to evaluate the results with care, and most of these tests or important aspects of them are fairly subjective. People with different levels of visual functioning may have the same vision-specific quality-of-life score [29, 30].

21  Quality of Life Following Glaucoma Drainage Device Surgery

21.4 Q  uality of Life in Glaucoma Patients Vision-specific instruments have greater ability to discriminate between glaucoma patients and normal subjects. They also correlate loss of visual field better when comparing both groups than the general health-related QoL instruments [4]. Glaucoma specific quality of life instruments have three general types of questions: one direct question regarding visual ability (e.g., “Have you noticed a decrease in your peripheral vision?” or “Do you have difficulty adjusting to a dark room?”), another aimed at task performance evaluation (e.g., “Does glaucoma limit your driving?” and “Do you have difficulties with household chores because of glaucoma?”), and a third one evaluating the importance of losing that given task performance and visual ability to the patient [4]. Tests that are used specifically for glaucoma are:

21.4.1 The GSS It is a ten-item checklist of symptoms common to glaucoma patients [31]. The symptomatic subscale includes burning/stinging, tearing, dryness, itching, soreness/tiredness, and foreign body sensation. The visual ability subscale includes blurry/dim vision, difficulty seeing in daylight and in darkness, and halos around lights. The patients are required to state how bothered they were by it. Glaucoma patients had significantly lower scores on both subscales of the GSS, scoring worse on the visual ability subscale [31]. Association between Esterman visual field and GSS scores was not significant. Contrast sensitivity correlated with daylight vision [32].

21.4.2 The Questionnaire of Viswanathan and Associates A ten-item questionnaire with a yes or no answer about visual field, deterioration in sight, color per-

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ception, bumping into objects and tripping, activities given up because of vision limitation, finding dropped objects, problems with glare/brightness, and transition to darkness is not yet validated formally, although objective correlations with patients with glaucoma were found [33].

21.4.3 The Symptom Impact Glaucoma (SIG) and Glaucoma Health Perceptions Index (GHPI) Both questionnaires developed for the CIGTS. The SIG has a total of 43 items covering four subscales: visual ability, local eye, systemic, and psychological [20]. The GHPI covers six items looking into the impact of the disease on physical, emotional, social, and cognitive components of health, glaucoma-­related stress, and concern about going blind [20].

21.4.4 The Glaucoma Quality of Life (GQL)-15 Questionnaire This questionnaire brings together the most often reported issues of daily living into four categories: outdoor mobility, glare/lighting conditions and activities that require peripheral vision, household tasks, and personal care. Responses correlated with visual field MD values, Pelli-­Robson contrast sensitivity values, and the Esterman visual field test scores [34]. Interestingly it found that decrease in visual ability was significantly reported more by patients with mild visual field loss when compared to normal patients, suggesting that glaucoma patients can distinguish even mild losses of visual field [34]. Medeiros et  al. established the association between NEI VFQ-25 and standard automated perimetry [3]. Subjects with a history of fast visual field progression were more likely to report lesser QoL scores when compared to patients with a slow VF progression [25]. It is likely that in subjects with slower VF progression, there would be more time for development of compensatory strategies that would reduce the impact of field loss on QoL. In the univariable model, each 1 dB

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of change in the binocular MS was associated with an average change of 2.9 units in NEI VFQ25 Rasch-calibrated scores. However, the amount of baseline visual field (VF) change was also an important factor influencing the impact of VF change in QoL. More severe the baseline, greater the changes in the NEI VFQ-25 scores [3]. The CIGTS approach to analyzing quality of life expected that symptomatic changes would precede clinical changes. Symptom status and vision-related functioning would be followed by more general health perceptions. The focus of that study was on symptom reporting and daily visual functioning based on the Visual Activities Questionnaire and the Symptom and Health Problem Checklist mainly [20]. VA changes have greater impact in quality of life as measured by the VEI VFQ-25. Some visual field data is limited to the eye that had surgery performed on and therefore enrolled in the study. It has been shown that binocular or better-eye visual status better predicts vision-­ specific quality of life [35, 36]. Evidence shows that often self-reported measures do not correlate well with clinical measures of function [35–37], and individuals with similar clinical status report different quality-of-life experiences [38].

21.5 Q  uality of Life Following Glaucoma Surgery CIGTS showed worst quality-of-life scores in surgical group compared with medical treatment group. The surgical group performed worst in three criteria: VAQ acuity, glaucoma local eye, and glaucoma total score subscales, although they had 0.1–2.5 differences in effect size when compared to baseline which represents a small clinical effect [20]. Females and elderly population report more problems with visual function-related activities [39, 40]. The frequency of bothersomeness evaluated within the local eye subscale was greater since baseline and through the 4 years of follow-up in the surgically treated group, which does not seem

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unexpected given the creation of the bleb. Initially, though, the CIGTS researchers hypothesized that the medication group would have worst scores given the local side effects of topical medication. Also, unlike patients who use medication for a long time before having a surgical procedure, this cohort did not previously experience the side effects of medical therapy and therefore could have been more susceptible to changes and symptoms that arouse from their surgical treatment. In summary, after 5  years of follow-up, the impact reported in QoL for both groups was quite similar. The differences observed initially after treatment diminished overtime. The worsening of clinical status was associated with change in reported symptoms and perception of visual function. The Tube vs. Trabeculectomy study is a multicenter randomized clinical trial used to compare the safety and efficacy of the glaucoma drainage device (GDD) and the conventional trabeculectomy with mitomycin C (MMC) in patients with previous ocular surgery [41]. The GDD used in the study was the 350 mm2 Baerveldt glaucoma implant (Abbott Medical Optics, Santa Ana, California, USA). The quality-of-life outcomes between the two treatment groups were included as a secondary outcome measure of this study. The MID in the NEI VFQ-25 was calculated for these patients with advanced disease to assess clinical changes overtime [18]. The TVT study found little difference in self-­ reported vision-specific quality of life between conventional trabeculectomy and tube shunt surgery in 5 years of follow-up. That suggests that patients are likely to experience some sort of stability postoperatively [18]. Similar findings were found in the CIGTS with early glaucoma and patients who had either early surgery or eye drops found no difference in the scores during the follow-up time [20].

21.6 Conclusion To date no significant vision-specific treatment group differences have been detected in the RCTs that evaluated quality of life in glaucoma sur-

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culty recognizing faces? Invest Ophthalmol Vis Sci. 2012;53(7):3629–37. 11. Kotecha A, O’Leary N, Melmoth D, Grant S, Crabb DP.  The functional consequences of glaucoma for eye-hand coordination. Invest Ophthalmol Vis Sci. 2009;50(1):203–13. 12. McGwin G Jr, Mays A, Joiner W, et al. Is glaucoma associated with motor vehicle collision involvement and driving avoidance? Invest Ophthalmol Vis Sci. 2004;45(11):3934–9. 13. Altangerel U, Spaeth GL, Steinmann WC. Assessment of function related to vision (AFREV). Ophthalmic Epidemiol. 2006;13(1):67–80. 14. Lorenzana L, Lankaranian D, Dugar J, et  al. A new method of assessing ability to perform activities of daily living: design, methods and baseline data. Ophthalmic Epidemiol. 2009;16(2):107–14. 15. Richman J, Lorenzana LL, Lankaranian D, et  al. Relationships in glaucoma patients between standard vision tests, quality of life, and ability to perform daily activities. Ophthalmic Epidemiol. 2010;17(3):144–51. References 16. Waisbourd M, Parker S, Ekici F, et al. A prospective, longitudinal, observational cohort study examining 1. Beauchamp GR, Felius J, Stager DR, Beauchamp how glaucoma affects quality of life and visually-­ CL.  The utility of strabismus in adults. Trans Am related function over 4 years: design and methodolOphthalmol Soc. 2005;103:164–71. ogy. BMC Ophthalmol. 2015;15:91. 2. Brown GC, Brown MM, Stein JD, Roth Z, 17. Musch DC, Lichter PR, Guire KE, Standardi Campanella J, Beauchamp GR.  The burden of age-­ CL.  The Collaborative Initial Glaucoma Treatment related macular degeneration. Trans Am Ophthalmol Study: study design, methods, and baseline charSoc. 2005;103:180–93. acteristics of enrolled patients. Ophthalmology. 3. Medeiros F, Gracitelli C, Boer E, Weinreb R, Zangwill 1999;106(4):653–62. L, Rosen P.  Longitudinal changes in quality of life 18. Kotecha A, Feuer WJ, Barton K, Gedde SJ, The and rates of progressive visual field loss in glaucoma Tube Versustrabeculectomy Study Group. Quality of patients. Ophthalmology. 2015;122:293–301. life in the tube versus trabeculectomy study. Am J 4. Spaeth G, Walt J, Keener J. Evaluation of quality of Ophthalmol. 2017;176:228–35. life for patients with glaucoma. Am J Ophthalmol. 19. Janz NK, Wren PA, Lichter PR, et  al. Quality of 2006;141(1 Suppl):S3–S14. life in newly diagnosed glaucoma patients: The 5. Appleby J, Devlin N.  Measuring success in the Collaborative Initial Glaucoma Treatment Study. NHS.  Using patient-assessed health outcomes to Ophthalmology. 2001;108(5):887–97. discussion manage the performance of healthcare providers. Dr. 898. Foster Ethics Committee London, UK; November 20. Baus S. Psychological aspects of visual impairment. 2004. http://www.staff.city.ac.uk/n.j.devlin/measurBr J Vis Impair. 1999;17:41–4. ing%20success%20in%20the%20NHS.pdf. Accessed 21. Owsley C, McGwin G Jr. Depression and the 10 Jul 2016. 25-item National Eye Institute Visual Function 6. Varma R, Richman EA, Ferris FL III, Bressler Questionnaire in older adults. Ophthalmology. NM.  Use of patient-reported outcomes in medical 2004;111(12):2259–64. product development: a report from the 2009NEI/ 22. Richman J, Lorenzana L, Lankaranian D, Dugar J, FDA Clinical Trial Endpoints Symposium. Invest Mayer J, Wizov S, Spaeth G.  Relationships in glauOphthalmol Vis Sci. 2010;51(12):6095–103. coma patients between standard vision tests, qual 7. Black N.  Patient reported outcome measures could ity of life, and ability to perform daily activities. help transform healthcare. BMJ. 2013;346:f167. Ophthalmic Epidemiol. 2010;17(3):144–51. 8. Parrish RK II, Gedde SJ, Scott IU, et al. Visual func- 23. Waisbourd M, Parker S, Ekici F, Martinez P, Murphy tion and quality of life among patients with glaucoma. R, Scully K, Wizov S, Hark L, Spaeth G.  A proArch Ophthalmol. 1997;115(11):1447–55. spective, longitudinal, observational cohort study 9. Jampel HD.  Glaucoma patients’ assessment of examining how glaucoma affects quality of life and their visual function and quality of life. Trans Am visually-related function over 4 years: design and Ophthalmol Soc. 2001;9:301–17. methodology. BMC Ophthalmol. 2015;15:91. 10. Glen FC, Crabb DP, Smith ND, Burton R, Garway-­ 24. Mangione CM, Lee PP, Gutierrez PR, et  al. Heath DF.  Do patients with glaucoma have diffiDevelopment of the 25-item National Eye Institute

gery or glaucoma drainage device implant. After 5 years of follow-up in both studies, the impact observed is remarkably similar. Quality of life is mainly affected when visual acuity is affected. However, there is limited data, and more studies are needed to establish the relationship properly. Regarding the quality-of-life questionnaires and tests, they should ideally explore responses that will distinguish patients with glaucoma from normal patients. They should also be able to correlate with performance-based measures of visual ability and clinical measures of disease progression. Reducing unnecessary questions lessens the assessment fatigability and reduces the cost of administration of the questionnaire.

154 Visual Function Questionnaire. Arch Ophthalmol. 2001;119(7):1050–8. 25. Gutierrez P, Wilson MR, Johnson C, et  al. Influence of glaucomatous visual field loss on health-related quality of life. Arch Ophthalmol. 1997;115:777–84. 26. Jaeschke R, Singer J, Guyatt GH.  Measurement of health status. Ascertaining the minimal clinically important difference. Control Clin Trials. 1989;10(4):407–15. 27. Revicki D, Hays RD, Cella D, Sloan J. Recommended methods for determining responsiveness and minimally important differences for patient-reported outcomes. J Clin Epidemiol. 2008;61(2):102–9. 28. Jampel HD, Schwartz A, Pollack I, et  al. Glaucoma patients’ assessment of their visual function and quality of life. J Glaucoma. 2002;11(2):154–63. 29. Friedman SM, Munoz B, Rubin GS, et  al. Characteristics of discrepancies between self-reported visual function and measured reading speed. Salisbury Eye Evaluation Project Team. Invest Ophthalmol Vis Sci. 1999;40(5):858–64. 30. Lee BL, Gutierrez P, Gordon M, et al. The glaucoma symptom scale: a brief index of glaucoma-specific symptoms. Arch Ophthalmol. 1998;116:861–6. 31. Noe G, Ferraro J, Lamoureux E, Rait J, Keeffe JE.  Associations between glaucomatous visual field loss and participation in activities of daily living. Clin Exp Ophthalmol. 2003;31:482–6. 32. Viswanathan AC, McNaught AI, Poinoosawmy D, et al. Severity and stability of glaucoma: patient perception compared with objective measurement. Arch Ophthalmol. 1999;117:450–4.

B. de Padua Soares Bezerra et al. 33. Nelson P, Aspinall P, Papasouliotis O, Worton B, O’Brien C.  Quality of life in glaucoma and its relationship with visual function. J Glaucoma. 2003;12:139–50. 34. Lisboa R, Chun YS, Zangwill LM, et al. Association between rates of binocular visual field loss and vision-­ related quality of life in patients with glaucoma. JAMA Ophthalmol. 2013;131:486–94. 35. Jampel HD, Friedman DS, Quigley H, Miller R.  Correlation of the binocular visual field with patient assessment of vision. Invest Ophthalmol Vis Sci. 2002;43(4):1059–67. 36. Okamoto M, Sugisaki K, Murata H, et  al. Impact of better and worse eye damage on quality of life in advanced glaucoma. Sci Rep. 2014;4:4144. 37. Mills RP, Janz NK, Wren PA, Guire KE. Correlation of visual field with quality-of-life measures at diagnosis in the Collaborative Initial Glaucoma Treatment Study (CIGTS). J Glaucoma. 2001;10(3):192–8. 38. Feinstein AR, Josephy BR, Wells CK. Scientific and clinical problems in indexes of functional disability. Ann Intern Med. 1986;105(3):413–20. 39. Kroenke K, Spitzer R.  Gender differences in the reporting of physical and somatoform symptoms. Psychosom Med. 1998;60:150–5. 40. Verbrugge LM, Patrick DL.  Seven chronic condi tions: their impact on US adults’ activity levels and use of medical services. Am J Public Health. 1995;85:173–82. 41. Gedde SJ, Singh K, Schiffman JC, Feuer WJ.  The Tube Versus Trabeculectomy Study: interpretation of results and application to clinical practice. Curr Opin Ophthalmol. 2012;23(2):118–26.

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Monica Gandhi, Anupma Lal, and Shibal Bhartiya

22.1 Introduction Trabeculectomy is considered as the gold standard filtering surgery for glaucoma. In recent times, there has been an increase in the number of glaucoma drainage devices (GDD) being implanted for both primary and refractory glaucomas [1–3]. The decision to choose between trabeculectomy and GDD, and further which GDD to implant, is often based on surgeons’ previous experience, preference and skill, and the patients profile. Randomised clinical trials (RCT) add to our knowledge in making a systematically reviewed rational choice. There are several studies done on various implants, but this chapter will focus on the three main RCTs, namely, the Ahmed Baerveldt Comparison (ABC) study, the Ahmed Versus Baerveldt (AVB) study and the Tube Versus Trabeculectomy (TVT) study.

M. Gandhi (*) Anterior Segment and Glaucoma Services, Department of Ophthalmology, Dr. Shroff’s Charity Eye Hospital, New Delhi, India A. Lal Lutheran Hospital, Fort Wayne, IN, USA S. Bhartiya Department of Ophthalmology, Fortis Memorial Research Institute, Gurgaon, India

© Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_22

The Ahmed glaucoma valve (AGV; New World Medical, Ranchos Cucamonga, CA) is a valved device with a tube, inserted in the anterior chamber, leading to the end plate (184 mm2) to which the aqueous is directed. The flow restrictor decreases the aqueous flow when the intraocular pressure is low. The Baerveldt glaucoma implant (BGI; Abbott Medical Optics, Abbott Park, IL) has a larger end plate (350  mm2) and has no valve; therefore it tends to have a lower IOP following the implantation and thus requires a ligature to moderate flow immediately after the surgery. Since the plate size of BGI is large, it requires implantation under the rectus muscles, and the surgical procedure becomes longer/difficult [4].

22.2 The Tube Versus Trabeculectomy (TVT) Study This was a prospective randomised multicentric trial to compare the efficacy and safety of trabeculectomy with mitomycin C (MMC) and Baerveldt glaucoma implant (BGI) 350  mm2. Two hundred and twelve patients between 18 and 85 years, with uncontrolled glaucoma (IOP ≥18 and ≤40  mmHg on maximal tolerated medical therapy) and previous failed filtering surgery and/ or cataract extraction with intraocular lens implantation, were included [5].

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The following patients were not included [5]: • • • • • • • • • • • • • • • • •

No light perception vision Pregnant or nursing women Active iris neovascularization Proliferative retinopathy Iridocorneal endothelial syndrome Epithelial or fibrous downgrowth Aphasia Vitreous in the anterior chamber for which a vitrectomy was anticipated Chronic or recurrent uveitis Severe posterior blepharitis Unwillingness to discontinue contact lens use after surgery Previous cyclodestructive procedure Prior scleral buckling procedure Presence of silicone oil Conjunctival scarring precluding a superior trabeculectomy Need for glaucoma surgery combined with other ocular procedures Anticipated need for additional ocular surgery

22.2.1 Definition of Failure IOP >21 and ≤5  mmHg or less than 20%  IOP reduction from baseline as measured on two consecutive visits after 3 months was considered as criteria for failure. Also included were reoperations or loss of light perception. This is similar to the ABC study but differed from the AVB study in terms of the target IOP.

22.2.2 Definition of Success The eyes that achieved the target IOP without additional glaucoma medication were considered complete success, and those that required therapy were classified as qualified success.

22.2.3 Results of the TVT Study [6, 7] For the analysis, patients who underwent additional glaucoma surgeries were excluded.

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Both trabeculectomy with MMC (n 105) and the BGI (n 107) produced a sustained, significant and comparable IOP reduction (p 0.097). At 5-year follow-up, the IOP (mean  ±  SD) was 14.4  ±  6.9  mmHg in the tube group and 12.6 ± 5.9 mmHg in the trabeculectomy group (p 0.12, 95% confidence interval −0.5  mmHg to 4.1 mmHg). The decrease in the number of glaucoma medications from baseline was 1.8 ± 1.8 in the tube group and 1.7 ± 2.0 in trabeculectomy group. Failure of treatment was documented in 33% of tube and 50% of trabeculectomy group. At 5 years, the cumulative probability of failure was 46.9% in the trabeculectomy group and 29.8% in the tube group. The reasons for failure were similar in both groups, and inadequate IOP lowering was the foremost cause of failure. Persistent hypotony and higher number of repetitions were observed more commonly in the trabeculectomy group. Since it was not a masked study, a potential surgeon bias is possible, but the coordinates studied that such a difference was not present in the patients who underwent reoperations. Twenty-five percent of patients achieved complete and 42% had qualified success in the tube group. Twenty-nine and 21% of patients achieved complete and qualified success, respectively, in the trabeculectomy group. Thus, the rates of complete success were comparable between the two groups with an overall higher rate of success in the BGI group.

22.3 Ahmed Baerveldt Comparison (ABC) Study The ABC study was a multicentric randomised controlled clinical trial which compared the long-­ term success, outcomes and complications of the two glaucoma drainage devices—the Ahmed glaucoma valve (AGV) and the Baerveldt glaucoma implant (BGI). Two hundred and seventy-six patients enrolled in 16 centres were randomised to either of the implants and were followed up for 5  years, thereby yielding prospective data comparing the devices in the control of glaucoma [8].

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One hundred and forty-three underwent surgical implantation of the AGV implant, and 133 of the Baerveldt implant amongst the patients enrolled between 2006 and 2008. Fifty-two percent were males, and the mean age  ±  standard deviation of age was 63  ±  14  years. The mean baseline IOP was 31.5 ± 11.8 mmHg. The only difference in the baseline demographics was the higher prevalence of hypertension in the AGV group (13%). Inclusion criteria [8]: patients 18–85 years of age with uncontrolled glaucoma (IOP > 18 mmHg) on maximal tolerated medical management and planned for GDD. The patients were randomised between the two implants; however, they were first stratified into four groups depending on the diagnosis:

22.3.2 Potential for Bias

1. Primary glaucomas with previous intraocular surgery 2. Secondary glaucomas (excluding neovascular and uveitic glaucomas) 3. Neovascular glaucoma 4. Uveitic glaucoma

22.3.3 At 1-Year Follow-Up [10]

Neither the subject nor the investigator was masked to the randomisation. The surgical procedure was allowed to be according to the surgeons’ skill, but certain steps were standardised to bring uniformity. These included the use of FP7 AGV and 101-350 BGI to be placed in the superotemporal quadrant, 8–10 mm posterior to the limbus. The placement of the BGI under or over the superior and lateral rectus and the type of occlusion of its tube were left to the surgeons’ discretion.

22.3.1 Definition of Failure Failure was defined as IOP more than 21 mmHg or less than 5 mmHg [9]. Other indicators were if the IOP was not reduced by 20% compared to the baseline and if the subject required additional glaucoma surgery or removal of the implant. Loss of light perception vision was also an indicator of failure.

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It was an unmasked study with the decision to reoperate based on the treating surgeon. The surgeons in the ABC study indicated that they had performed more than 20 GDD implantations. Those reporting to have done less than five were included after screening of their surgical videos. This led to a small effect on the rate of complications reported  by the surgeons  with  different levels of experience. Analysis of results at end of 1 year, showed that experienced surgeons had 20% less likelihood of complications in the AGV  implantation and 30%  less likelihood if they were skilled to implant BGI [10].

The cumulative probability of failure was 16.4% (standard error [SE], 3.1%) in the AGV group and 14.0% (SE, 3.1%) in the BGI group at 1 year (p 0.52). More patients experienced early postoperative complications in the BGI group (n 77; 58%) compared to the AGV group (n 61; 43%; p 0.016). Serious postoperative complications associated with reoperation (8% of AGV and 1% of BGI group), vision loss of two Snellen lines (30% of AGV and 34% of BGI group), or both in 29 patients (20%) in the AGV group and in 45 patients (34%) in the BGI group (p 0.014). The most frequent causes of decrease in vision at 1  year were glaucoma, macular disease and cataract. The vision loss was higher in the patients of neovascular glaucoma stratum and those who had a better preoperative visual acuity. Postoperative interventions were more in the BGI group (11% versus 6%) but were not statistically significant (p = 0.077). Thus at 1  year  follow up, the IOP lowering was better, and lesser reoperations were needed for elevated IOP in the BGI group, but this came at a price of more serious complications than the AGV group. If the efficacy and complications are taken together, the study does not prove one

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implant to be clearly superior than the other. And since the significance level of the study was set at 0.05, there is a probability that the results occurred by chance alone [10]. The results at the end of 5-year follow-up are depicted in Table 22.1. They are compared with the results of the AVB study.

22.4 T  he Ahmed Versus Baerveldt (AVB) Study The AVB study was a prospective randomised multicentric clinical trial including 238 patients. Ten surgeons from seven clinical centres implanted the AGV FP 7 and the BGI 350 mm2

Table 22.1  Comparison of parameters between ABC and AVB study AT 5 years Number of patients (at the beginning of the study)

IOP (mean ± SD) (mmHg) No. of glaucoma medications in use Cumulative probability of failure during 5 years of follow-up No. of subjects failing because of inadequate IOP or reoperation

Eyes with vision-threatening complications Change in logarithm of minimum angle of resolution visual acuity Complete success (IOP control without medication)

ABC study

AGV 143

BGI 133

AVB study

124

114

ABC study AVB study ABC study

14.7 ± 4.4 16.6 ± 5.9 2.2 ± 1.4

12.7 ± 4.5 13.6 ± 5.0 1.8 ± 1.5

p value 63% completed the 5-year follow-up 72% completed the 5-year follow-up 0.015 0.001 0.28

AVB study ABC study

1.8 ± 1.5 44.7%

1.2 ± 1.3 39.4%

0.03 0.65

AVB study ABC study

53% 46 (80% of AGV failures)

40% 25 (53% of BGI failures)

0.04 0.003

AVB study

AVB study ABC study

45% failed due to high IOP. 0% due to hypotony 15% required de novo glaucoma surgery 11 (20% of AGV failures) 6% 0.42 ± 0.99

23% failed due to high IOP 4% due to hypotony 10% required de novo glaucoma surgery 22 (47% of BGI failures) 8% 0.43 ± 0.84

AVB study ABC study

8%

14%

2% complete success 12% qualified success

4% complete success 19% qualified success

ABC study

AVB study

0.97

0.49 (complete success) 0.12 (qualified success)

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depending on the randomisation. The patients in both groups were matched in their demographic and ocular characteristics except that there was a greater proportion of females in the BGI group. The patients were older than 18 years and had uncontrolled refractory glaucoma despite the conventional medical, laser or surgical treatment. Patients not eligible for trabeculectomy with antifibrotic agents were included, like active neovascular glaucoma and patients with significant conjunctival scarring [11].

22.4.1 Definition of Failure IOP higher than 18 mmHg or lower than 5 mmHg or less than 20%  IOP reduction from baseline was included in the definition of failure. This was recorded at two consecutive visits at or after 3 months. If the patients required additional glaucoma surgery or needed device explantation, it was considered a failure along with if there was  loss of light perception and associated vision-­threatening complications. In ABC study the range of acceptable IOP was >5 and 21 mmHg was considered in ABC and >18  mmHg in AVB study. The cumulative probability of failure at 5 years was comparable when the IOP criteria were matched [22]. Both studies concluded that the BGI leads to a greater long-term IOP control compared to the AGV. The two studies thus validate the findings of each other due to similar results.

22.5.6 Can We Choose Between AGV and BGI Based on the ABC Study? The study suggests that with the BGI, a lower IOP in the long term can be achieved and it may be considered in patients where a lowest possible IOP is desired postoperatively. But if the safety and efficacy are considered, the study does not demonstrate a clear choice between the two implants. They recommend the surgeon to choose based on the individual patient characteristics, and his skill and experience with each implant. One cannot disregard the complications possible with the implants and the benefits based on the preoperative diagnosis. The choice between the valved and non-valved would be based on the urgency to lower the IOP, again based on the patient characteristics.

22.5.7 Can We Choose Between AGV and BGI Based on the AVB Study? Baerveldt implant leads to an IOP 3 mmHg lower than the Ahmed implant, and also the glaucoma

22  Important Clinical Trials in Glaucoma Drainage Devices

medication needed is a median of 1 compared to 2 in AGV at the end of 5 years. The loss of two of more lines of vision was noted in 43% of the Ahmed group and 46% of the Baerveldt group. Both groups had high postoperative complication rates, but most ­ required minimal interventions or were transient. The study coordinators recommend that when a low long-term IOP is desired and if patients are intolerant to topical medications, Baerveldt implant is a good choice. However, postoperatively the patient may require a meticulous follow-­up to manage complications. In patients where immediate lowering of IOP is required, Ahmed valve works best. This may, however, have to be substantiated with medications and additional glaucoma surgery. But it is also recommended that the final choice be based on patient diagnosis and risk factors for failure, the IOP which will preserve optic disc health, and the surgeons’ skill and familiarity with the chosen implant.

22.5.8 Does TVT Help in Making a Choice Between Tube and Trabeculectomy? The study demonstrates efficacy of both trabeculectomy and tube in the subset of patients included but does not prove superiority of one over the other. It supports the practice pattern shift of greater tube shunt usage by glaucoma surgeons based on the patient characteristics and the doctors' skill. It helps in choosing a tube implant in a patient where a previous filtering surgery has failed.

22.5.9 What Are the Limitations of the ABC Study? It is not a masked study therefore, the surgeon bias could have played a role. The surgeons enrolled to operate had experience with each type of implant, but those who had performed less than five surgeries were also included. It was noted that the rate of complications was higher in the latter group. There could also be variation due

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to techniques used by the surgeon as the procedure was not completely standardised. This study was focused on the two implants; thus the results cannot be extrapolated to the other designs and models. The results do not apply to the diagnostic groups not included in the study, namely, the subjects who have a low risk for standard trabeculectomy. The analysis excluded patients if they required a reoperation, explanation of implant or lost perception of light.

22.5.10  What Are the Limitations of the AVB Study? The patients at high risk of failure were recruited, so the results cannot be applied to the patients in the early stages of the disease where the glaucoma drainage devices are being used more often now. The definition of success was based on visual acuity and not the sensitive predictors of optic nerve health such as automated perimetry. But this would be true for other studies too as the baseline vision of refractory glaucoma patients is expected to be low. The AVB study coordinators suggest that the results of their study do not suggest supremacy of any device and that a meticulous understanding of the clinical stage of the patient and balancing it with the other criteria are required.

22.5.11  What Are the Limitations of the TVT Study? The patient selection was very limited, and it did not include patients with factors which increase risk of failure. The results therefore, cannot be extrapolated to the patients with characteristics different from those included in this study. It was an unmasked study with standardisation of only a part of the surgeries, giving the surgeons latitude to perform it according to their skill and comfort and also to decide on criteria for reoperations. The dose of MMC used was higher (0.4  mg/ml for 4  min) than what is currently used, and it could be a reason for hypotony and rates of failure.

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22.6 Summary The RCTs help in making an informed choice of the surgical intervention for management of glaucoma. The studies do not give a clear superiority of any procedure and suggest that the final decision can be based on the patient characteristics and surgeons’ experience.

References 1. Ramulu PY, Corcoran KJ, Corcoran SL, Robin AL.  Utilization of various glaucoma surgeries and procedures in Medicare beneficiaries from 1995 to 2004. Ophthalmology. 2007;114:2265–70. 2. Chen PP, Yamamoto T, Sawada A, et al. Use of antifibrosis agents and glaucoma drainage devices in the American and Japanese Glaucoma Societies. J Glaucoma. 1997;6:192–6. 3. Desai MA, Gedde SJ, Feuer WJ, et al. Practice preferences for glaucoma surgery: a survey of the American Glaucoma Society in 2008. Ophthalmic Surg Lasers Imaging. 2011;42:202–8. 4. Minckler DS, Francis BA, Hodapp EA, et al. Aqueous shunts in glaucoma: a report by the American Academy of Ophthalmology. Ophthalmology. 2008;115:1089–98. 5. Gedde SJ, Schiffman JC, Feuer WJ, et al. The Tube Versus Trabeculectomy Study: design and baseline characteristics of study patients. Am J Ophthalmol. 2005;140(2):275–87. 6. Gedde SJ, Schiffman JC, Feuer WJ, et al. Tube Versus Trabeculectomy Study Group. Treatment outcomes in the Tube Versus Trabeculectomy (TVT) Study after five years of follow-up. Am J Ophthalmol. 2012;153:789–803. 7. Gedde SJ, Herndon LW, Brandt JD, et al. Postoperative complications in the Tube Versus Trabeculectomy (TVT) study during five years of follow-up. Am J Ophthalmol. 2012;153:804–814.e1. 8. Barton K, Gedde SJ, Budenz DL, et  al. Ahmed Baerveldt Comparison Study Group. The Ahmed Baerveldt Comparison Study: methodology, baseline patient characteristics, and intraoperative complications. Ophthalmology. 2011;118:435–442. 9. Heuer DK, Barton K, Grehn F, et  al. Consensus on definitions of success. In: Shaarawy TM, Sherwood MB, Grehn F, editors. Guidelines on design and reporting of surgical trials. World Glaucoma

M. Gandhi et al. Association. Amsterdam, The Netherlands: Kugler; 2008. p. 15–24. 10. Budenz DL, Barton K, Feuer WJ, et  al., Ahmed Baerveldt Comparison Study Group. Treatment outcomes in the Ahmed Baerveldt Comparison Study after 1 year of follow-up. Ophthalmology. 2011;118:443–452. 11. Christakis PG, Tsai JC, Zurakowski D, et  al. The Ahmed Versus Baerveldt study: design, baseline patient characteristics, and intraoperative complications. Ophthalmology. 2011;118:2172–9. 12. Christakis PG, Kalenak JW, Zurakowski D, et al. The Ahmed Versus Baerveldt study: one-year treatment outcomes. Ophthalmology. 2011;118:2180–9. 13. Christakis PG, Tsai JC, Kalenak JW, et al. The Ahmed versus Baerveldt study: three-year treatment outcomes. Ophthalmology. 2013;120:2232–40. 14. Christakis PG, Kalenak JW, Tsai JC, Zurakowski D, Kammer JA, Harasymowycz PJ, et  al. The Ahmed Versus Baerveldt Study: five-year treatment outcomes. Ophthalmology. 2016;123:2093–102. 15. Budenz DL, Barton K, Gedde SJ, et  al. Five-year treatment outcomes in the Ahmed Baerveldt comparison study. Ophthalmology. 2015;122:308–16. 16. Freedman J, Iserovich P. Pro-inflammatory cytokines in glaucomatous aqueous and encysted Molteno implant blebs and their relationship to pressure. Invest Ophthalmol Vis Sci. 2013;54:4851–5. 17. Choritz L, Koynov K, Renieri G, et al. Surface topographies of glaucoma drainage devices and their influence on human tenon fibroblast adhesion. Invest Ophthalmol Vis Sci. 2010;51:4047–53. 18. Heuer DK, Lloyd MA, Abrams DA, et  al. Which is better? One or two? A randomized clinical trial of single-plate versus double-plate Molteno implantation for glaucomas in aphakia and pseudophakia. Ophthalmology. 1992;99:1512–9. 19. Molteno AC, Fucik M, Dempster AG, Bevin TH. Otago Glaucoma Surgery Outcome Study: factors controlling capsule fibrosis around Molteno implants with histopathological correlation. Ophthalmology. 2003;110:2198–206. 20. Britt MT, LaBree LD, Lloyd MA, et al. Randomized clinical trial of the 350-mm2 versus the 500-mm2 Baerveldt implant: longer term results: is bigger better? Ophthalmology. 1999;106:2312–8. 21. Seah SKL, Gazzard G, Aung T.  Intermediate-term outcome of Baerveldt glaucoma implants in Asian eyes. Ophthalmology. 2003;110:888–94. 22. Christakis PG, Zhang D, Budenz DL, Barton K, Tsai JC, Ahmed II, ABC-AVB Study Groups. Five-­ year pooled data analysis of the Ahmed Baerveldt Comparison Study and the Ahmed Versus Baerveldt Study. Am J Ophthalmol. 2017;176:118–26.

Newer Devices for Aqueous Drainage

23

Reena Choudhry, Isha Vatsal, and Foram Desai

23.1 Introduction Glaucoma is the leading cause of irreversible blindness worldwide [1, 2]. Though trabeculectomy still remains the “gold standard” in glaucoma surgery, it is associated with significant morbidity such as hypotony and bleb-related complications [3–5]. With this background, there has been a constant search for alternative procedures that are less invasive and safer, have optimal IOP-lowering effect, and improve quality of life in patients with chronic glaucoma. The algorithm of glaucoma treatment, therefore, is experiencing a gradual shift from conventional trabeculectomy to minimally invasive glaucoma surgery (MIGS). These procedures aim at either overcoming the resistance at the juxtacanalicular meshwork, increasing uveoscleral outflow via suprachoroidal pathway, or creating a subconjunctival drainage pathway [6]. MIGS appears to provide a safer, less invasive means of reducing IOP than traditional trabeculectomy in patients with glaucoma [2]. Currently, results suggest that these procedures tend to achieve moderate IOP-lowering effect and are ideal when a very low target IOP is not the requirement [1]. Typically, all the MIGS procedures are indicated in the eyes with primary

R. Choudhry (*) · I. Vatsal · F. Desai ICARE Eye Hospital and Post Graduate Institute, Noida, India © Springer Nature Singapore Pte Ltd. 2019 M. Gandhi, S. Bhartiya (eds.), Glaucoma Drainage Devices, https://doi.org/10.1007/978-981-13-5773-2_23

open-angle glaucoma and are generally performed in combination with cataract extraction. This chapter aims to summarize the current options for MIGS and provides an overview on their effectiveness and safety. MIGS and Its Key Features • Ab interno approach with assistance • Safer • Minimally invasive • Conjunctival sparing • Rapid recovery • Largely bleb independent

gonioscopic

Indications • Primary open-angle glaucomas • Secondary open-angle glaucomas like pigmentary glaucoma, pseudoexfoliation glaucoma • Mild-to-moderate disease • Glaucoma with coexisting cataract

Contraindications • Primary and secondary glaucomas • Advanced glaucomas • Previous glaucoma surgery • Need for low target IOP

angle-closure

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23.1.1 Classification of MIGS 1. Procedures increasing trabecular outflow by bypassing the juxtacanalicular trabecular meshwork (TM) • Trabectome • iStent • Hydrus • Excimer laser trabeculotomy (ELT) • Gonioscopy-assisted transluminal trabeculotomy(GATT) 2. Procedures increasing uveoscleral outflow via suprachoroidal pathway • CyPass Micro-Stent 3. Subconjunctival drainage pathway • XEN Gel Stent

23.2 Trabectome Trabectome was approved by the US Food and Drug Administration (FDA) and introduced in 2004. It uses a high-frequency (550 kHz) bipolar electrocautery to ablate a strip of trabecular meshwork (TM) and the inner wall of Schlemm’s

Irrigation Port

canal (SC), thus reestablishing access to the eyes’ natural drainage system. It removes the area of greatest resistance to the aqueous outflow and can be performed simultaneously with cataract surgery [7, 8].

23.2.1 Design Trabectome comes with a 19.5-gauge disposable handpiece with an insulated footplate containing electrocautery, irrigation, and aspiration functions (Fig. 23.1). It creates a 200 μm plasma cloud between the rod and the outer electrode. Heat dissipation is restricted by the outer footplate; thus, the heat damage does not occur in the deeper parts of the TM [9]. About 90°–120° area can be treated through a single incision.

23.2.2 Procedure A 2 mm flared clear corneal incision is made. The anterior chamber is formed with saline.

a. Handpiece b. Power, IA Line c. Irrigation/Aspiration Unit d. High Frequency Generator e. Clean Tray f. Main Control g. Foot Control a

Protective Footplate

b

c d

Aspiration Part

e

Retum Electrode Active Electrode

f

g

Fig. 23.1 Trabectome

23  Newer Devices for Aqueous Drainage

Viscoelastic is not recommended for AC reformation as it (1) creates a blur by forming optical interfaces, (2) makes it harder to induce hypotony to visualize the Schlemm’s canal, and (3) traps plasma gas bubbles, thus interfering with electrocautery. Under direct gonioscopic visualization, the tip is inserted in irrigation mode into the Schlemm’s canal, and the electrocautery and aspiration are activated by pressing the foot pedal. The TM is cauterized by advancing the tip in clockwise direction followed by anticlockwise. In general, 90°–120° is treated in a single sitting. Incision is sutured to ensure water tight closure.

23.2.3 Key Advantages • • • •

Rapid recovery Can be performed with cataract surgery No implant No antimetabolite

23.2.4 Complications IOP spikes on first postoperative day and hyphema are the most common complications. Iris and lens touch and goniosynechiae are other listed complications [10]. Delayed-onset hyphema (2–30 months following the procedure) has been reported and attributed to Valsalva maneuver, the use of aspirin and warfarin, and IOP below episcleral venous pressure [11].

23.2.5 Efficacy Data Minckler et  al. [12] examined the outcomes of Trabectome alone versus combined procedures with phacoemulsification based on data from 1127 surgeries performed at 46 study sites since January 2006. At 24  months, IOP dropped by 40% from 25.7  ±  7.7  mmHg preoperatively to 16.6 ± 4.0 mmHg in the Trabectome alone group compared to 30% from 20.0  ±  6.2  mmHg to 14.9  ±  3.1  mmHg in the combined phaco-­ Trabectome group. Mean number of medications decreased from 2.9 to 1.2  in the Trabectome

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group and from 2.6 to 1.5 in the combined group. A total of 14% (100 patients) were considered failure cases from Trabectome alone group. Robust data from well-designed randomized controlled trials are awaited.

23.3 Excimer Laser Trabeculotomy (ELT) ELT (excimer laser trabeculotomy) is another form of ab interno trabeculotomy which uses 308  nm xenon chloride pulsed excimer laser to create micro-perforations in the TM and inner wall of Schlemm’s canal. It uses a photo-ablative approach to vaporize the TM.

23.3.1 Design The laser device comes in two forms. The first device uses a gonioscopy lens to visualize the TM, while the second device comes with an endoscopic laser probe for direct visualization. Eight to ten laser burns are placed over 90°, approximately 500  μm from one another. Each pulse delivers a mean energy of 1.2 mJ and is of 80 ns duration over a spot size of 200  μm.

23.3.2 Procedure A 1.2 mm corneal incision is made and viscoelastic is injected into the AC. Laser probe is inserted with its tip-up. When it is 2 mm away from the angle, place goniolens to visualize the TM. Laser tip is contacted with TM, and 8–10 laser spots are placed over 90°. Micro-perforations and reflux of blood are considered an end point of treatment.

23.3.3 Key Advantages • • • • •

Rapid recovery Can be performed with cataract surgery No implant No antimetabolite No interference with future surgeries

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23.3.4 Complications

23.4 iStent

Micro-bleeding can occur intraoperatively after the laser is applied and is usually transient. In the available studies, no serious adverse events were reported.

The iStent (Glaukos Corporation, Laguna Hills, CA, USA) is a device designed to overcome the outflow resistance at the trabecular level by creating a direct communication between the anterior chamber and Schlemm’s canal. iStent is a FDA-­ approved surgical implant and is indicated in patients with mildto-moderate open-angle glaucomas. The procedure can be done de novo or simultaneously with cataract surgery.

23.3.5 Efficacy Data Babighian et al. in their prospective randomized controlled 2-year study compared 180° of treatment by ELT with selective laser trabeculoplasty (SLT). Mean IOP reduction at 2 years was 29.6% in the ELT group versus 21% in the SLT group. Glaucoma medications were reduced from 2.27 ± 0.7 to 0.87 ± 0.8 in the ELT group compared to a reduction from 2.20  ±  0.7 to 0.87  ±  0.8  in the SLT group. Success rates, defined by ≥20% IOP reduction without additional glaucoma intervention, were 53.3% for the ELT group compared to 40% for the SLT group [13].

23.4.1 Design iStent is a heparin-coated, non-ferromagnetic implant made of surgical grade titanium. It is 1  mm in length and 0.3  mm in height, and the lumen has a diameter of 120 μm; it has a ridged, snorkel design with three retention arches on its outer surface for secure placement (Fig. 23.2a). A second-generation model called the iStent

b

a Snorkel 0.3 mm Ope

nH

Ret

Lumen 120 µm

enti

on A

rche

s

alf P

ipe

Self-Trephining Tip

ACTUAL SIZE

c

Fig. 23.2 (a) Design of an iStent. (b) Picture showing the actual size of iStent. (c) iStent snorkel sits parallel to the iris plane, and iStent rails are seated against scleral wall of Schlemm’s canal

23  Newer Devices for Aqueous Drainage Fig. 23.3  Design of iStent inject

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Inlet orifice

Outflow orifices (4 total)

Thorax Flange (resides in anterior chamber) (resides in trabecular meshwork)

inject (Fig.  23.3) has been available, and the inserter comes preloaded with two stents allowing the injection at the same time without exiting the eye.

23.4.2 Procedure The inserter is introduced through a 1.7 mm clear corneal incision under viscoelastic cover. The device is injected into the Schlemm’s canal under gonioscopic view. The anterior chamber is cleared of the viscoelastic.

23.4.3 Key Advantages • • • • • •

Rapid recovery Can be performed with cataract surgery No antimetabolite No interference with future surgeries Excellent safety profile Minimal risk of hypotony

23.4.4 Complications IOP spike which is generally transient, intraoperative blood reflux from Schlemm’s canal, and Stent malposition and obstruction are some of the reported complications [14].

Head (resides in Schlemm’s canal)

23.4.5 Efficacy Data The US iStent Study Group performed a prospective randomized controlled multicenter clinical trial, in which 240 eyes have mild-to-moderate glaucoma. The eyes were randomized to iStent combined with cataract surgery versus cataract surgery alone. The percent IOP reduction was 8.0% with 87.0% medication reduction in the iStent-cataract group at 12 months compared to 5.5% IOP reduction and 73.0% medication reduction in the cataract group. At 1 year, 72% of the stent/CE/IOL group had unmedicated IOP ≤21  mmHg, compared to 50% of CE/IOL-group eyes (P