Adult glaucoma surgery da luz, freitas maria [srg]

Adult Glaucoma Surgery

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTDNew Delhi • London • Philadelphia • Panama

®

Foreword

Matthias C Grieshaber

Guests

João Eurico Lisboa MD

Ex-Chairman Department of Ophthalmology

Hospital Santo António dos CapuchosLisbon, Portugal

Queiroz Marinho MD

Ex-Chairman Department of Ophthalmology

Hospital Geral de Santo AntónioPorto, Portugal

Editor

Maria da Luz Freitas MD

Consultant Department of Ophthalmology

Hospital da ArrábidaPorto, Portugal


Jaypee Brothers Medical Publishers (P) Ltd

HeadquartersJaypee Brothers Medical Publishers (P) Ltd4838/24, Ansari Road, DaryaganjNew Delhi 110 002, IndiaPhone: +91-11-43574357Fax: +91-11-43574314Email: [email protected]

Overseas Offices

J.P. Medical Ltd Jaypee-Highlights Medical Publishers Inc. Jaypee Brothers Medical Publishers Ltd83, Victoria Street, London City of Knowledge, Bld. 237, Clayton The BourseSW1H 0HW (UK) Panama City, Panama 111 South Independence Mall EastPhone: +44-2031708910 Phone: +507-301-0496 Suite 835, Philadelphia, PA 19106, USAFax: +02-03-0086180 Fax: +507-301-0499 Phone: + 267-519-9789Email: [email protected] Email: [email protected] Email: [email protected]

Jaypee Brothers Medical Publishers (P) Ltd Jaypee Brothers Medical Publishers (P) Ltd17/1-B Babar Road, Block-B, Shaymali Shorakhute, KathmanduMohammadpur, Dhaka-1207 NepalBangladesh Phone: +00977-9841528578Mobile: +08801912003485 Email: [email protected]: [email protected]

Website: www.jaypeebrothers.comWebsite: www.jaypeedigital.com

© 2013, Jaypee Brothers Medical Publishers

All rights reserved. No part of this book and DVD-ROMs may be reproduced in any form or by any means without the prior permission of the publisher.

Inquiries for bulk sales may be solicited at: [email protected]

This book has been published in good faith that the contents provided by the contributors contained herein are original, and is intended for educational purposes only. While every effort is made to ensure accuracy of information, the publisher and the editor specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the contents of this work. If not specifically stated, all figures and tables are courtesy of the editor. Where appropriate, the readers should consult with a specialist or contact the manufacturer of the drug or device.


First Edition: 2013

ISBN: 978-93-5090-355-1

Printed at:

®

Dedicated to

My husband, António Marinho

In the middle of the 19th century, von Graefe, the renowned ophthalmologist from Berlin, proposed considering performing the first surgical intervention for glaucoma: an iridectomy. A filtration operation also emerged in that century—the Lagrange operation. This was favored by my father, who had learned the procedure from Prof Gama Pinto. It involved an incision similar to what was then performed for cataract, with a von Graefe knife; but, it was deliberately prolonged to the sclera, with conjunctival flap and sector iridectomy. A filtering cicatrix was thus obtained. In the 1940s, the filtration operation preferred by Dr Sertório Sena, who was my teacher, was the Elliot operation. After preparing a conjunctival flap, a hole was made next to the limbus with a small trephine. An operation introduced in 1906 by Holth, was usually performed in the 1950s: Iridencleisis. After creating a conjunctival flap, an incision was made, perforating the limbus and a sector iridectomy performed, placing the two pillars of the iris between sclera edges. A filtering cicatrix was thus formed, with good tension outcome but cosmetically unsatisfactory. It was abandoned after some cases of sympathetic ophthalmia were reported and ascribed to this operation. A little later, Scheie's operation was introduced. It was widely used and afforded good results in terms of tension. A limbal incision under a conjunctival flap, alternating cauterization and a blade. A small peripheral iridectomy as soon as a small prolapse of the iris occurred. This was only abandoned with the arrival of the elegant trabeculectomy procedure, which is still in use today. Several minor modifications have been suggested, the most important being the addition of mitomycin C, to ensure better filtration. A procedure that has been used increasingly in more complicated cases, especially re-operations, is the placing of tubes in the anterior chamber, draining the aqueous humor to sites further away. It was recognized that there were two kinds of glaucoma once the gonioscopy started to be used in the middle of the last century. Peripheral iridectomy was proposed, and widely used, for cases of closed angle glaucoma. Until the arrival of laser treatment, which presently gives the same outcome, but more simply and safely. A word about congenital glaucoma. Around the year 1950, Barkan proposed goniotomy to treat this disorder. Trabeculotomy emerged later, and both are widely used.

João Eurico Lisboa MD

Ex-ChairmanDepartment of Ophthalmology

Hospital Santo António dos Capuchos Lisbon, Portugal

Reminiscences

Open Angle GlaucomaIf we go back to 1949, in those days, two procedures were basically used to treat open angle glaucoma. The Lagrange operation, which was on its way out, and the Elliot oper-ation. The first consisted of puncturing the cornea with a von Graefe knife from 2 to 11 o’clock and then making an incision to 12 o’clock, cutting a flap of sclera and continu-ing under the conjunctiva to create a conjunctival flap. After this, the knife is withdrawn, cutting the conjunctiva and finally a fragment of sclera, previously cut, is removed with a pair of curved forceps. A peripheral iridectomy is then performed, and then the conjunctiva is finally sutured. In the Elliot operation, a limbus-based conjunctival flap was dissected and then the sclera was trephined next to the limbus at 12 o’clock with a 1.5 or 2 mm diameter trephine. A peripheral iridectomy was performed and finally the conjunctiva was sutured. The main problems with these two techniques include having direct communication without any pro-tection from the anterior chamber to the subconjunctival space, which often led to marked loss of pressure, emptying of the anterior chamber, possibility of infection, draining of the vitreous humor if the sclera holes were slightly posterior, hemorrhage and the possibility of loss of the scleral button, in the Elliot operation. We should not forget that all these procedures were carried out without a microscope, and only occasionally with the aid of a magnifying glass, and so the vast majority were conducted with the naked eye. We started to circumvent these problems by carrying out iridencleisis. This involved creating a limbus-based conjunctival flap, an incision of the sclera 3 mm from the limbus penetrating the anterior chamber and, using forceps, holding the iris next to the sphincter, it was pushed outside; and then, using another forceps, the iris was split to create two ‘pillars’ which were pushed into the scleral incision. Suturing of the conjunctiva: with this operation, tension control was more predictable, but it entailed two major problems: first, esthetically, the eye looked ugly, with one pupil open in the shape of an inverted keyhole, often causing photophobia because the sphincter of the iris was no longer functioning; second, uveitis sometimes appeared due to irritation from the incarcerated iris. The Stallard operation was introduced in the 1950s, to try and get round these problems. This involved creating a limbus-based conjunctival flap, a scleral incision of about 3 mm one millimeter from the limbus, proceeding with a peripheral iridectomy and incarceration of the pillar of the iris in the scleral incision. The conjunctiva is then sutured. This operation vastly improved the surgical panorama of glaucoma, as the sphincter was conserved, the incidence of uveitis was greatly reduced and tension controls improved. In the early 1970s, Cairns devised the trabeculectomy procedure. This operation, which I shall not describe here because it has reigned supreme in open angle glaucoma for over 30 years, is known to one and all. In most cases it is an effective operation, with loss of the anterior chamber or, rarely, the absence of a filtration bleb sometimes occurring as a complication. In the early 1960s, Krasnov described a technique that he called sinusotomy, which consisted of excising a fragment of sclera at the level of the Schlemm’s canal, thereby open-ing this canal directly to the subconjunctival space. Another operation, much less widely used, was the Scheie operation. In this procedure, after making a conjunctival flap based on the limbus and undertaking a partial scleral incision 1 mm from the limbus, com-pleting the perforation with cautery so as to simultaneously separate the lips of the scleral wound, peripheral iridectomy was performed and the conjunctiva then sutured. And this is where we are in terms of general open angle glaucoma surgery, according to my personal experience.

Reminiscences

Adult Glaucoma Surgeryx

Closed Angle GlaucomaWe can divide this situation, i.e. closed angle glaucoma into two: acute phase, when peripheral iridectomy is performed after using intravenous mannitol to reduce the likelihood of perioperative complications (expulsive hemorrhage, for example), and the subacute or chronic phase, which is treated with peripheral iridectomy or laser iridotomy.

Glaucoma in AphakicsCyclodialysis was used in aphakic glaucoma. It consisted of opening the conjunctiva and making an incision about 3 mm long in the sclera about 8 or 9 mm from the limbus, through which a spatula is introduced and directed towards the anterior chamber through the suprachoroidal space until it reached the anterior chamber. At this point, the spatula was turned through 90 degrees to create a direct path from the anterior chamber to the suprachoroidal space. Suturing of the conjunctiva: this operation had very varied outcomes in terms of tension and its major drawback was that it led to hyphema. This was slight in most cases and tended to be reabsorbed in two or three days, but if the hyphema was very large, paracentesis was required to drain the blood and prevent hematic infiltration of the cornea.

Absolute and Neovascular GlaucomaIn absolute and neovascular glaucoma, the first treatment was cyclodiathermy, and afterwards cyclocryo - coagulation was used. Results were very variable and these treatments were the last resort in eyes that were to all intents and purposes, lost.

Congenital GlaucomaA few words about congenital glaucoma, which is always treated surgically. The first in line is Barkan’s gonio-tomy, which is sometimes hard to do with a microscope, but its main problem is opacity of the cornea due to edema, and so trabeculotomy ab externo was introduced. The conjunctiva is opened, with a base on the limbus, cutting the sclera inwards to a depth of about 2 mm to expose Schlemm’s canal. This is then channelled with a probe, which is rotated towards the anterior chamber to cut through Barkan’s membrane, which fills the camerular angle. This procedure is repeated on the other side of Schlemm's canal to create a camerular angle of about 140 degrees. Suturing of the conjunctiva. Complications: there may be slight hyphema, which is reabsorbed in a few days. The effect on tension is good in most cases, and a week ago I happened to review two cases operated on 30 years ago, with an excellent outcome. And this is where my experience of glaucoma surgery, about 59 years of it, comes to an end.

Queiroz Marinho MD

Ex-ChairmanDepartment of Ophthalmology

Hospital Geral de Santo António Porto, Portugal

Manuela Carvalho MDHospital Graduate Assistant in Ophthalmology, Lisbon, Portugal

Arabela Futre Coelho MDHospital Graduate Assistant Department of OphthalmologyInstituto Oftalmológico Dr Gama Pinto (IOGP), Lisbon, Portugal

Pedro Faria MDHospital AssistantCentro de ResponsabilidadeIntegrada de Oftalmologia do CentroHospital Universitário de Coimbra (CHUC)Coimbra, Portugal

Teresa Gomes MDHospital Graduate AssistantDepartment of OphthalmologyCentro Hospitalar de Lisboa Central (CHLC) Lisbon, Portugal

Maria Reina MDHospital Graduate AssistantDepartment of OphthalmologyCentro Hospitalar de Lisboa Central (CHLC) Lisbon, Portugal

ContributorsA Rodrigues Figueiredo MDConsultant Department of OphthalmologyHospital de Santa Maria (CHLN) andLisbon School of MedicineLisbon, Portugal

Maria da Luz Freitas MDConsultantDepartment of OphthalmologyHospital da ArrábidaPorto, Portugal

After decades of stagnation, glaucoma surgery has gained momentum thanks to innova-tions and technical advances. It has all started when nonpenetrating procedures led by deep sclerectomy have become accepted alternatives to trabeculectomy. Recently, the increasing demand for safer surgery with low complication profiles generated minimally invasive procedures that aim to enhance the natural outflow pathway of the trabecular meshwork and Schlemm's canal, rather than creating a new drainage system. This book provides a fresh take on modern glaucoma surgery. Each chapter is clearly structured, is easy to read and comprehensive. Beautiful illustrations further guide the reader step-by-step through the surgical procedures which brings instant understanding, also for those not being familiar with the techniques. I am delighted to see how the authors recognized and skilled glaucoma surgeons share their invaluable knowledge about indications, techniques and pitfalls of their preferred surgery. What this book distinguishes from other books on glaucoma surgery is that it is written from a practical perspective of the surgeon. The authors reveal their precious tips for everyday surgical life which will be very helpful for the beginners, doctors in practice and glaucoma specialists. I trust you will enjoy reading this novel book which is both informative and practical.

Matthias C Grieshaber MD FEBO FMH Ophth

Senior PhysicianDepartment of Ophthalmology

University of BaselSwitzerland

Foreword

“It can be very difficult to sculpt the idea that you have in your mind. If your idea doesn’t match the shape of the stone, your idea may have to change because you have to accept what is available in the rock…Sometimes thinking about the carving takes longer than the carving itself.”

(Ovilu Tunnillie, artesão de arte Inuit, Fevereiro, 1999, in Arctic Spirit, Ingo Hessel)

Trabeculectomy ab externo has been the standard choice in terms of both initial and repeat surgery in any type of glaucoma. Even though good results are achieved with this procedure, it is not without its difficulties, complications and failures… It may be because of this, or because humans are restless beings, not reconciled to things, that there is a constant quest to find new procedures that can reduce these difficulties, complica-tions and causes of failure; the search is on to find procedures that are as close as possible to the physiological mechanisms that drain aqueous humor. Over time, scarring modulators have appeared, minimizing one of the causes of surgical failure. And while the first drainage devices, such as the Molteno and Ahmed shunts, were introduced to respond to the more complicated cases, the development of new devices and the appearance of new materials have made this surgical technique the first choice for some surgeons. The appearance of a nonpenetrating filtration surgical technique (deep sclerectomy) has reduced the number of perioperative complications and helped to make the postoperation period easier for patients and speeded-up their return to active life, as has extracapsular cataract extraction vs phacoemulsification surgery. Another minimally invasive procedure (ExPRESS™) has been introduced, which despite being still pene trating, normalizes the drainage of aqueous humor. Not forgetting the universal concept of ideal surgery as being that which restores the physiological mechanisms that are failing for some reason, the canal surgery techniques have run their course. Some take an internal approach, less comprehensive in terms of Schlemm's canal, but leave no scar and do not require use of the conjunctiva: trabeculotomy ab interno (Trabectome®) and trabecular microbypass (iStent®). Others have an external approach: viscocanalostomy and canaloplasty. Canaloplasty has been replacing viscocanalostomy since it enables a 360-degree approach to the Schlemm’s canal, which makes it a more comprehensive and more physiological technique. None of these procedures relies on the formation of filtration blebs. Many of the new surgical procedures leave out the type of glaucoma traditionally called narrow or closed angle. Here, too, with the appearance of new diagnostic methods, there has been a change in thinking, classi-fication and surgical approach. The idea of publishing a book and DVD-ROMs pooling different approaches and surgical techniques used by some Portuguese glaucomatologists for adult glaucoma came into being through the exchange of experiences during short surgical courses and wetlabs promoted by Alcon Portugal, as well as the increasing relevance of little tricks to increase the efficacy of our performance. This little book does not set out to be either a treatise on surgery or a compilation of all the surgical techniques used for adult glaucoma and their variations. This little book sets out to shed light on the new surgical possibilities that are available, bringing the personal stamp of each participant to the readers. Since we cannot evolve without knowing our past, I invited two masters and leading specialists in Portuguese ophthalmology, Dr João Eurico Lisboa and Prof Queiroz Marinho, to share their evidence with us.Finally, I hope this little book will be useful.

Maria da Luz Freitas

Preface

Everything that we are is the outcome of a series of factors and circumstances, in addition to ourselves. It would not be fair, therefore, to ignore the people who have played a part in my professional career, and to whom I am deeply grateful. I would like to thank the following, in particular:Dr João Eurico Lisboa and Prof Queiroz Marinho, who accepted the challenge of sharing their testimony with us; the Alcon Portugal laboratory, which has been the driving force behind this project; M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, that gave us the possibility to make this work internationally known; and, most especially, my husband, Prof António Marinho, for his wisdom and serenity.

Acknowledgments

1. Trabeculectomy 1 Pedro Faria

• Indications and Contraindications 1 • Preoperative Assessment 2 • Surgical Technique 2 – Anesthesia 2 – Opening of the Conjunctiva 2 – Scleral Flap 2 – Paracentesis 2 – Sclerectomy 3 – Iridectomy 3 – Conjunctival Closure 3 • Methods to Prevent Scarring of the Filtration Bleb 3 – Antimetabolites 3 – Bleb-forming Implants 4 – Anti-VEGFs 4 • Intraoperative Complications 4 – Hyphema 4 – Athalamia 4 – Vitreous Loss 4 – Expulsive Hemorrhage 5 • Immediate Postoperative Complications 5 – Hypothalamia with Ocular Hypotony 5 – Hyphema 5 – Choroidal Detachment 5 – Hypotonic Maculopathy 5 – Hypothalamia with Ocular Hypertony 5 – Suprachoroidal Hemorrhage 6 – Intraocular Infection 6 – Ocular Hypertension 6 – Encapsulated Bleb 6 • Late Postoperative Complications 6 – Late Hypotony 6 – Cataracts 7

Contents

Adult Glaucoma Surgeryxx

2. ExPressTM—Mini Glaucoma Shunt 8 Arabela Futre Coelho

• Indications 8 • Contraindications 9 • Surgery 9 – Anesthesia 9 – Surgical Technique 9 • Postoperative Therapy 10 • Complications 12 – Intraoperative 12 – Postoperative 12

3. Posterior Drainage Devices 14 Manuela Carvalho

• Device Characteristics 14 – Presence or Absence of a Flow Restriction Mechanism (Restrictive Versus Nonrestrictive) 14 – Plate Surface Area 15 – Composition 16 • Classic Indications 16 – Eyes in which Trabeculectomy with Mitomycin C (MMC), even with Adjunctive Antimetabolite Use, Have a High-Risk of Failure 16 – Eyes in which Trabeculectomy is Technically Not Possible or Has a High-Risk of Intraoperative Complications 16 – Patients in whom Trabeculectomy with MMC Has a very High-Risk of Postoperative Complications 16 • Recent Indications 16 – Relative Contraindications 17 • Preoperative Assessment 17 • General Assessment 17 • Types of Anesthesia 17 • Surgical Technique 17 – Globe Fixation 17 – Conjunctival Flap 17 – Plate Insertion and Fixation 18 – Paracentesis 18 – Tube Insertion 18 – Tube Covering 18 – Conjunctival Suture 19 • Technique Variants 19 – Tube Insertion in the Posterior Chamber 19 – Tube Insertion in the Pars Plana 19 – Technique Variations to Avoid Early Postoperative Hypotony (Nonvalved Implants) 19 – Use of Antiscarring Agents 20

Contents xxi

• Postoperative Complications 20 – Early Hypotony 20 – Transient Hypertensive Phase 20 – Tube- or Plate-related Complications 20 – Other Complications of Glaucoma Surgery 21

4. Deep Sclerectomy 23 Maria da Luz Freitas

• Indications 24 – Strictu Sensu 24 – Relative Contraindications 25 – Absolute Contraindications 25 • Patient's Assessment 25 • Surgical Technique 25 • Difficulties/Complications and their Intraoperative Resolution 30 – Depth of Deep Scleral Flap 30 – Perforation of Trabeculodescemetic Window 30 • Immediate Postoperative Complications and Resolution of Complications (1–10 Days) 30 – Seidel 30 – Inflammation 30 – Hypotony 31 – High Intraocular Pressure 31 – Choroidal Detachment 31 – Low Anterior Chamber 31 – Hematic Tyndall/Hyphema 31 – Descemet's Membrane Detachment 31 – Reduced Visual Acuity 31 • Late Postoperative Complications and Resolution of Complications (2–5 Weeks) 31 – Increased Intraocular Pressure 31 – Blebitis 31

5. Gonioscopic Surgery: Trabecular Micro-Bypass Stent Implantation 33 A Rodrigues Figueiredo

6. Canaloplasty 37 Maria da Luz Freitas

• Indications 37 • Relative Contraindications 37 • Absolute Contraindications 37 • Patient's Assessment 38 • Surgical Technique 38 – Preoperative Preparation 38 – Surgery Location 38

Adult Glaucoma Surgeryxxii

– Scleral Flaps, Opening of Schlemm's Canal Opening and Creation of a Trabeculodescemetic Window 40 – Catheterization, Dilation and Distention of Schlemm's Canal 41 – Closure of Scleral Flap and Conjunctiva 41 – Difficulties/Complications and their Intraoperative Resolution 44 – Immediate Postoperative Complications and Resolution of Complications (1–10 Days) 45 – Late Postoperative Complications and Resolution of Complications (2–5 Weeks) 46

7. Combined Surgery 48 Teresa Gomes

• Indications and Contraindications 48 • Patient's Clinical Evaluation 49 • Surgical Technique amd Complications 50

8. Lens Surgery in Glaucoma 55 Maria Reina

• Indications and Contraindications 55

• Clinical Evaluation or Patient Evaluation 57 • Description of Surgical Technique, Difficulties and their Resolution 59 • Immediate Postoperative Complications and Resolution of Complications 62

Index 65

INTRODUCTION

Trabeculectomy is the most widely used surgical option for glaucoma at a global level. The reasons for its success are its efficacy, relatively low cost and vast experience. Since this surgery has been performed for over 40 years, and therefore there is immense accumulated knowledge of its results, complications and resolution of these complications. The need to avoid the complications and the development of better surgical equipment have led to several changes and improvements to the original technique, described by Cairns in 1968.1 The aim of trabeculectomy is not merely to achieve intraocular pressure (IOP), low enough to stop or delay glaucoma progression. Like any glaucoma therapy, it must also take into account that visual function, and therefore quality of life, should be preserved. Therefore, surgical benefits (probability of surgery success) as well as the risk of complications and failure have to be considered (Table 1.1). Patient’s life expectancy must be weighed together with the disease progression rate and the risks and benefits of alternative therapies.2

This procedure was designed to overcome the so-called blockage of the external drainage of aqueous humor, which is usually located at the level of the

juxtacanalicular tissue of the trabecular meshwork (to Schlemm’s canal). It does not apply to cases in which the normal internal flow of humor is blocked (ciliary or pupillary block).

INDICATIONS AND CONTRAINDICATIONS

The most common clinical indication for trabeculectomy is disease progression despite maximum medical and laser therapies tolerated by the patient3 (Table 1.2). Such surgery is often chosen when it is anticipated that it will not be possible to manage the clinical case using the usual medical alternatives. This is especially the case for very young patients, a very high IOP or a very advanced disease stage on diagnosis.2 Trabeculectomy can also be selected to end a refractory hypertensive acute event or as an initial approach for congenital glaucoma (as an addition to trabeculotomy). However, there are situations in which trabeculectomy may not be the optimal therapeutic alternative (Table 1.3). This includes patients who have already undergone one or two trabeculectomies (especially if an antimetabolite has been applied) resulting in failure.

Table 1.1: Factors in surgical decision-making

• Patient’slifeexpectancy

• Diseaseprogressionrate

• Risksandbenefitsofalternativetherapies

• Risk/benefitoftrabeculectomy

Table 1.2: Indicationsfortrabeculectomy

• Failure of medical and surgical therapies to controlprogressivedisease

• When theusualmedical alternativesarenot expected tosucceed (youngpatients, very high IOP, very advanceddisease)

• Refractoryacutehypertensiveevent

• Congenitalglaucoma(combinedwithtrabeculotomy)

Pedro Faria

Trabeculectomy 1

AdultGlaucomaSurgery2

Furthermore, when the risk of vision loss (for surgical complication) is high and may significantly affect quality of life, as in single eye cases or potential loss of professional activity, a trabeculectomy might not be the best option.2 In these cases, a usually safer (although less effective) operation could be performed. Other cases of relative contraindication for trabeculectomy are those where failure or severe complication risks are predictably very high, such as in neovascular or uveitic glaucoma. Here, a drainage device can be implanted, which is usually more effective (and safer, when valved).

PREOPERATIVE ASSESSMENT

Trust in their ophthalmologist or surgical team is the most reassuring aspect for the patient. Trust is gained when patients receive a good explanation of the state of their disease, surgical therapy proposed and surgery goal (preserving vision), not to mention the potential risks, including vision or even eye loss. A careful, thorough ophthalmological and medical clinical history must be taken. A full ophthalmological examination is also needed.

SURGICAL TECHNIQUE

The ab externo trabeculectomy described here is a variant of the Cairns trabeculectomy as modified by Watson. This is the first-line surgery for glaucoma, and the operation which we perform the most in our glaucoma clinic. The goal is to obtain a protected fistula between the anterior chamber (AC) and the subconjunctival space.

Anesthesia

In most cases, surgery can be performed with retrobulbar or peribulbar locoregional block by injecting 0.5% bupivacaine (which can be combined with 2% lidocaine). In these cases, the patient generally receives prior sedation and topical anesthesia from an anesthetist. In addition, general anesthesia is often used, especially in pediatric patients, young adults or noncollaborating patients.

Opening of the Conjunctiva

Before this step, traction of the superior rectus muscle is performed by passing a suture (silk 4/0) below the muscle and tying a knot with the loose suture ends around a Kocher’s forceps. The knot will be hanging and ensure muscle traction during surgery, thereby facilitating a better exposure of the upper perilimbic area. Conjunctival opening is performed with Wescott scissors at approximately 7 mm from the limbus, corresponding to a limbus-based conjunctival flap (Fig. 1.1).

Scleral Flap

Upper location, around 12 o’clock, is for the filtration bleb to remain under the upper lid. This reduces infection rate as well as leaving an adjacent space for a further trabeculectomy or placing a drainage device tube in case of failure. Scleromalacia areas or large blood vessels are avoided. After “cleaning” the Tenon capsule, hemostasis of the cut sclera was obtained by vessel cauterization with a bipolar device. The flap is achieved by quadrangular incision (4 × 4 mm) with limbic hinge using a Beaver mini-blade, to obtain a flap thickness of about 1/3 to 1/2 of the scleral thickness and to expose the gray area of the corneal-scleral transition (Fig. 1.2).

Paracentesis

This is performed at the beginning of the operation to slowly decompress the AC, thus avoiding sudden decompression at the time of trabeculectomy. It is performed using a 15° blade in the cornea, next to the temporal limbus.

Table 1.3: Relativecontraindicationsfortrabeculectomy

• Previoustrabeculectomyfailure

• Highriskoffailure

• Highriskofsurgicalcomplications

• Whenpotentialvisionlossdramaticallyaffectsqualityoflife(singleeye/potentiallossofprofessionalactivity)

Fig. 1.1: Semicircular opening of the conjunctiva 7/8 mm from the limbus

Trabeculectomy 3

Sclerectomy

Using the same blade, a rectangular incision (1.5 × 3 mm) is made perpendicular to the ocular surface, which includes the corneal-scleral transition area. The forceps clamping the rectus muscle are removed to prevent the corresponding pressure over the ocular globe. After entering the AC, the sclerectomy is completed with Vannas scissors, maintaining a balanced salt solution (BSS) drip over the area to help hemostasis (Fig. 1.3).

Iridectomy

Peripheral iridectomy is performed clamping the iris with a colibri forceps and cutting with scissors (Fig. 1.4). The AC is replenished with BSS. The scleral flap is sutured (Nylon 10 or 9/0) with a stitch in each corner of the flap. The suture should be tightened so that it can coapt the flap and allow it to drain humor from the opening.

Conjunctival Closure

A continuous, tight closure suture (with Vicryl or Nylon) is applied to ensure leakproofness of the filtration bleb (watertight suture, Fig. 1.5).

METHODS TO PREVENT SCARRING OF THE FILTRATION BLEB

Antimetabolites

The most important factor in long-term IOP control is surgical wound scarring. As inhibitors of the scarring process, antimetabolites considerably increase the efficacy of classic trabeculectomy.4 However, this comes

Fig. 1.2: Cutting a scleral flap of 1/3 of the scleral thickness Fig. 1.3: Sclerectomy with scissors, excising the trabecular area

Fig. 1.4: Peripheral iridectomy with scissors

Fig. 1.5: Conjunctival closure with watertight suture


at a price: a higher incidence of complications such as infection, hypotony, and thin, cystic blebs with fluid leaks3 (Table 1.4). Therefore, glaucoma cases in which the risk-benefit ratio favors the use of antimetabolites (Table 1.5) are the most difficult and more prone to failure: uveitic, neovascular, traumatic, congenital, and infantile-juvenile glaucoma, as well as previous surgery. Currently, 5-fluorouracil and mitomycin C (MMC) are the most commonly used antimetabolites. The author uses MMC (0.2 mg/mL) on a small sponge, which he applies for 1–2 minutes over the sclera and scleral bed of the flap before sclerectomy. Caution is essential when handling MMC and the area must be flushed with plenty of BSS after application.

Bleb-Forming Implants

Implants made of reabsorbable materials (such as OculusGen and Ologen) are available. These can be easily applied next to the scleral flap to delay scarring and facilitate formation of a good filtration bleb.

Anti-VEGFs

Neovascular glaucoma is a condition with a poor surgical prognosis due to vascularization, high associated pressures and fast postoperative scarring. Anti-vascular-endothelial growth factor (VEGFs) inhibitors injected intraocularly 1 week before trabeculectomy cause marked neovascularization regression, which gives surgeons a time frame for higher surgical safety, especially preventing perioperative bleeding.

INTRAOPERATIVE COMPLICATIONS

Hyphema

Hyphema is very frequent, especially if the ciliary body is damaged during the trabeculectomy itself.

In general, intraoperative bleeding can be prevented if antiaggregation or anticoagulation medication is suspended approximately 10 days beforehand. Another cause of intraocular bleeding is sudden ocular decompression, which can also be minimized by paracentesis. This mostly happens in very high preoperative IOP cases, which can be treated with oral acetazolamide or by injecting a hyperosmotic agent immediately before surgery (125 cc mannitol 20%, IV). If the eye is inflamed, a topical vasoconstrictor drug (e.g. brimonidine) can also be applied immediately before surgery. Balanced salt solution should be constantly dripped during and immediately after sclerectomy in that area to facilitate hemostasis. The hyphema must be suctioned and the AC replenished with BSS, or preferably air, since this is more effective in anterior segment hemostasis. Most of these considerations also apply to the prevention of hemorrhagic choroidal detachment.

Athalamia

Another common complication is intraoperative athalamia, which also occurs after sudden decompression or when larger-scale trabeculectomy is performed, or even due to careless pulling of eye structures or unnecessary pressure on the eye. The AC must be restored as often as needed throughout the surgery. If there is a risk of iridocorneal or corneal-lenticular contact at the end of the operation, and it is impossible to restore the AC with BSS or air, a viscoelastic material can be injected to maintain the chamber and/or the scleral flap can be further sutured, taking care to hydrate the edges of the paracentesis entry port. Any conjunctival damage should be sutured, because a gap will cause a fluid leak from the bleb, with all its consequences. For this reason, conjunctival manipulation should be performed with the utmost care throughout the surgery.

Vitreous Loss

Although relatively rare, vitreous loss is a complication which may compromise the success of this surgical technique. It happens most often when vitreous is already present in the anterior segment following trauma or complicated cataract surgery. However, vitreous loss may occur without previous vitreous identification, especially in a pseudophakic eye. A careful, open vitrectomy should be performed using Wecker scissors.

Table 1.4: Complicationsfromtheuseofantimetabolitesintrabeculectomy

• Cysticandthin-walledblebs(withleaks)

• Hypotonyanditscomplications

• Blebitisandendophthalmitis

Table 1.5: Indicationsfortheuseofantimetabolitesintrabeculectomy

• Uveiticglaucoma

• Neovascularglaucoma

• Traumaticglaucoma/previoussurgery

• Congenitalandinfantile/juvenileglaucoma

Trabeculectomy 5

Expulsive Hemorrhage

Although expulsive hemorrhage is one of the rarest complications, it is certainly the most feared of all. It is a form of rapid-onset suprachoroidal hemorrhage in the intraoperative period,5 and it is most common in aphakic and pseudophakic eyes. Any ocular incision must be closed as soon as possible and a posterior sclerotomy must be performed at once to drain blood and avoid extrusion of intraocular contents.

IMMEDIATE POSTOPERATIVE COMPLICATIONS

The success of a trabeculectomy does not depend merely on an uneventful procedure, the immediate postoperative follow-up is also important,6 particularly for the detection and resolution of common complications7 (Table 1.6).

Hypothalamia with Ocular Hypotony

This usually results from hyperfiltration and upon rest only, the normal height in the AC chamber is restored and IOP rises within two weeks after surgery. In case of athalamia with iridocorneal apposition the chamber must be restored as soon as possible. This can be achieved through the surgical paracentesis entry port to avoid corneal decompensation. When hypothalamia is caused by fluid loss through a conjunctival gap or suture dehiscence, the safest approach is to suture the lesion.

Hyphema

Anterior segment bleeding may occur in the first 3–5 days after surgery and it usually resolves with no particular intervention rather than rest. Large hyphemas more often cause clots, which are usually drained by flushing the AC. This can be performed through a 2 mm paracentesis.

Choroidal Detachment

This complication, which is frequently associated with hypotony and hypothalamia,8 may be exudative or hemorrhagic. Spontaneous resolution is common when resolving hypothalamia, with rest, cycloplegia and corticoid therapy. However, when it is persistent and significant, it may require surgical drainage by sclerotomy.

Hypotonic Maculopathy

This complication accompanies persistent hypotony and causes vision loss. Choroidal folds can generally be observed with fundoscopy. Therefore, this may happen soon after trabeculectomy, or later. First of all, the cause of hypotony must be known so that the right treatment is chosen. It may be necessary to resuture the scleral flap to raise the IOP as quickly as possible.

Hypothalamia with Ocular Hypertony

This rare complication occurs especially in chronic closed-angle glaucoma cases treated surgically, as well as in microphthalmia. It is generally due to an increase in volume and pressure behind the iridolenticular diaphragm, which in turn may have several causes: pupillary block due to incomplete iridectomy, choroid or suprachoroidal space expansion (by exudate or blood), and ciliary block. In case of pupillary block, a patent iridotomy must be created. For ciliary block (generally designated as malignant glaucoma), its resolution in approximately half the cases is medically obtained by cycloplegia, topical corticoid therapy and maximum ocular hypotensive medication.9 If resolution is not achieved within 4–5 days, vitreous suction or pars plana vitrectomy is required.

Table 1.6: Surgicalcomplicationsoftrabeculectomy

Intraoperative Immediate Postoperative Late

Hyphema Hypotonichypothalamia Hypotony

Athalamia Hyphema Cysticbleb

Conjunctivaldamage Choroidalbleeding Blebitis

Vitreous loss Choroidaldetachment Endophthalmitis

Expulsivehemorrhage Hypotonicmaculopathy Hypotonicmaculopathy

Hypertonichypothalamia Cataracts

Blebitis/Endophthalmitis

Hypertony

Encapsulatedbleb


Suprachoroidal Hemorrhage

Fortunately, this is a rare event. However, it happens more frequently in some types of eyes: traumatized, vitrectomized, aphakic, highly myopic (>26 mm) or congenital glaucoma. Risk factors are also anticoagulant therapy or preoperative IOP (>35 mm Hg). Clinically, it occurs within 4–5 days after surgery and patients complain of painful vision loss, with high IOP. Resolution is often achieved by drainage through posterior sclerotomy.

Intraocular Infection

This is another rare complication which may occur in the immediate postoperative period or many years after trabeculectomy. The risk factors are: antimetabolite use,10 very thin or leaky blebs and blebs outside the upper fornix. When the infection is confined to the bleb with minimal AC reaction, this is usually called blebitis and generally responds to antibiotics.11 In cases of posterior segment invasion and a classical picture of endophthalmitis, aspirative vitreous biopsy and intraocular injection of antibiotics are required.

Ocular Hypertension

Filtration block may occur anytime during the first weeks after surgery. This may result from surgical complications (usually occurring within the first week) or simply from vigorous scarring of operated tissues. If the AC is well formed, a gonioscopy should be performed to check if anything is blocking the trabeculectomy exit (such as a clot or part of the iris). If blockage is caused by the iris, treatment with pilocarpine is initiated; if this fails, argon laser is applied in the iris to the surgical wound. A clot may be released by applying pressure with a spatula in the posterior area of the sclerotomy. When nothing seems to be blocking the exit, there may be an overtight suture in the scleral flap, which can be resolved by laser suture lysis. Flap scarring may also be present. In the early postoperative period, the filtration process may be rescued by applying what is known as ocular massage.12 The patient is shown how to perform anteroposterior digital pressure on the upper lid, over the bleb, and to repeat this several times a day.

Encapsulated Bleb

This complication occurs in approximately 10% of cases, usually in the 2nd and 5th week postoperatively.

The bleb is well-formed, inflamed and tense, with a well-formed AC and gradually increasing intraocular tension. Such bleb encysting is more common with a limbus-based conjunctival flap and is often resolved with drugs which decrease the production of aqueous humor and topical corticoid therapy.13 When encysting cannot be resolved medically, an intervention known as needling is performed.14

Needling Technique

This intervention is performed in the surgical block, in an outpatient setting and under topical anesthesia with prior injection of 2% lidocaine in the conjunctiva next to the bleb. A 27-gauge needle (in a 2 mL syringe) is inserted in the conjunctiva, posterior to the bleb. The needle is advanced with lateral movements in the edge of the bleb. If the needle point and scleral flap can be seen clearly, patency of the trabeculectomy can be confirmed and a point can be cut from the flap, if indicated. Finally, 5-fluorouracil15 or MMC can be injected (0.1 mL injection of 0.02 mg/mL MMC), laterally into the bleb, taking care to avoid the drug entering the AC.

LATE POSTOPERATIVE COMPLICATIONS

Late Hypotony

This complication is usually associated with a hyperfiltrating, thin-walled, cystic bleb which can be easily perforated, resulting in leakage of aqueous humor and higher susceptibility to infection16 and hypotonic maculopathy (Table 1.6). These blebs are more frequent when antimetabolites are applied.17 Clinically, the patient may complain of vague discomfort, watering eyes especially at night, and oscillopsia. Sometimes it is not easy to detect the leak, but a Seidel test is generally positive. Small orifices can be closed by applying eye drops to diminish the production of aqueous humor, topical antibiotic therapy and a therapeutic contact lens, and the patient should be advised to return as soon as signs of infection appear, since infection is the main risk of this condition. For large leak orifices or when the previous therapy has failed, several other therapies have been described: autologous blood injection in the bleb,18 compressive suture, application of trichloroacetic acid or of the so-called “biological glue”. These measures often fail or are only temporarily successful, requiring surgical revision with conjunctivoplasty after excision of most of the cystic bleb.

Trabeculectomy 7

Cataracts

The incidence of cataract formation is higher after trabeculectomy than after other glaucoma surgical procedures, such as nonpenetrating glaucoma surgery.3 This seems to be due to a higher complication rate involving the anterior segment.

FINAL REMARKS

Two-year success rates for trabeculectomy are approximately 90% in surgery-naive eyes operated on by experienced surgeons.19 However, the ophthalmologist must weigh the risks and benefits expected from the trabeculectomy for each particular case. The use of antimetabolites has significantly increased trabeculectomy efficacy, but it must be borne in mind that complications are also more frequent.

REFERENCES

1. Cairns JE. Trabeculectomy: Preliminary report of a new method. Am J Ophthalmol. 1968;5:673-9.

2. Stamper RL, et al. Glaucoma outflow procedures. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas, 7th edition. St Louis: Mosby; 2009. p. 466.

3. Heijl A, Traverso C, et al. Incisional surgery. European Glaucoma Society. Terminology and Guidelines for Glaucoma, 3rd edition. Savona, Italy: Dogma; 2008. p. 153.

4. Fontana H, et al. Trabeculectomy with mitomycin C: outcomes and risk factors for failure in phakic open-angle glaucoma. Ophthalmology. 2006;113(6):930-6.

5. Chu T. Expulsive and delayed suprachoroidal hemorrhage. In: Charlton J, Weinstein G (Eds). Ophthalmic Surgery Complications. Philadelphia: Lippincott-Raven; 1995.

6. Edmunds B, et al. The National Survey of Trabeculectomy. III. Early and late complications. Eye. 2002;16(3):297-303.

7. Vesti E. Filtering blebs: follow up of trabeculectomy. Ophthalmic Surg. 1993;24:249-55.

8. Lieberman M. Complications of glaucoma surgery. In: Charlton J, Weinstein G (Eds). Ophthalmic Surgery Complications. Philadelphia: Lippincott-Raven; 1995.

9. Yaqub M, et al. Malignant glaucoma. In: El Sayyad F, et al. (Eds). The Refractory Glaucomas. New York: Igaku-Shoin; 1995.

10. Greenfield DS, Suner IJ, Miller MP, et al. Endophthalmitis after filtering surgery with mitomycin. Arch Ophthalmol. 1996;114:943-9.

11. Chen PP, Gedde SJ, Budenz DL, et al. Outpatient treatment of bleb infection. Arch Ophthalmol. 1997;115:1124-228.

12. Kane H, Gaasterland DE, Monsour M. Response of filtered eyes to digital ocular pressure. Ophthalmology. 1997;104:202-6.

13. Costa VP, Correa MM, Kara-Jose N. Needling versus medical treatment in encapsulated blebs: a randomized, prospective study. Ophthalmology. 1997;104:1215-20.

14. Gillies WE, Brooks AMV. Restoring the function of the failed bleb. Aust N Z J Ophthalmol. 1991;19:49-51.

15. Broadway DC, Bloom PA, Bunce C, et al. Needle revision of failing and failed trabeculectomy blebs with adjunctive 5-fluorouracil: survival analysis. Ophthalmology. 2004;111(4):665-73.

16. Kangas TA, Greenfield DS, Flynn HW, et al. Delayed-onset endophthalmitis associated with conjunctival filtering blebs. Ophthalmology. 1997;104:746-52.

17. Jampel HD, McGuigan LJ, Dunkelberger GR, et al. Hypotony maculopathy following trabeculectomy with mitomycin-C (letter). Arch Ophthalmol. 1992;110:1049.

18. Choudhri SA, Herndon LW, Damji KF, et al. Efficacy of autologous blood injection for treating over filtering or leaking blebs after glaucoma surgery. Am J Ophthalmol. 1997;123:554-5.

19. Lichter PR, Musch DC, Gillespie BW, et al. CIGTS Study Group. Interim Clinical Outcomes in the Colla- bo rative Initial Glaucoma Treatment Study (CIGTS) comparing initial treatment randomized to medi-cations or surgery. Ophthalmology. 2001;108:1943-53.

Adult Glaucoma Surgery8

INTRODUCTION

The basic principles for the use of any kind of drainage implant are based on permanent sclerotomy and introduction of a tube in the anterior or posterior chamber to drain aqueous humor from the limbal area into an equatorial sub-Tenon space.1,2 The ExPressTM mini glaucoma shunt was initially designed by Belkin and Glovinsky for placement in the anterior chamber under a conjunctival flap, but it soon became necessary to change this approach to a guarded subscleral implant. The shunt consists of a nonvalved, biocompatible stainless steel tube (316 LVM) similar to that used in cardiology stents and MRI-compatible. The image shows the evolution of ExPressTM (Figs 2.1A to D). Only model P is marketed in Europe. The shunt has an outer diameter of 400 µm (equivalent to a 27-gauge needle), inner diameter between 50 µm and 200 µm, and its length varies between 2.64 mm and 2.96 mm. The distal end may be sharp or blunt according to the model, and it has a small spur-like extension to prevent extrusion. The proximal end exhibits a disk shape, which varies according to the model. The disk fixes the implant and prevents it from penetrating the anterior chamber. Moreover, the distal portion contains accessory lateral orifices which serve as an alternative in case of obstruction of the main central lumen. The distance between the ends is approximately that of the thickness of the sclera in the limbus area. The main goal of the implant is to allow a constant, standardized drainage of aqueous humor, which cannot

Figs 2.1A to D: Evolution of ExPressTM

be achieved with classic trabeculectomy, which gives greatly variable results from surgeon to surgeon. This technique is also much less invasive than trabeculectomy since there is no excision of trabecular or iris tissue. Furthermore, the learning curve is very short compared with the so-called nonpenetrating surgery, which, despite being less invasive has a longer learning curve. We may rate the ExPressTM implant as a “minimally invasive surgery” (MIS) about half-way between trabeculectomy and nonpenetrating surgery techniques.

INDICATIONS

In general, filtration surgery is the option of choice after failure of maximum medical and/or laser treatment, as well as intolerance to medical therapy or suspected poor compliance.3

Arabela Futre Coelho

2ExPressTM— Mini Glaucoma Shunt

A

C

B

D

ExPressTM—Mini Glaucoma Shunt 9

The truth is that this concept has partially changed after the advent of nonpenetrating and minimally penetrating surgery, since hypotensive results are identical with fewer complications. So why put off an early surgical approach if the secondary effects of hypotensive eye drops on the conjunctiva are well-known and postsurgical results in a healthy conjunctiva are better? Simple chronic glaucoma is the most frequent form and also the main indication for this technique. Pigmentary glaucoma (more frequent in myopic young male adults) and pseudoexfoliative glaucoma are conditions whose respective pathophysiological mechanisms consist of obstructing drainage pathways with pigmentary deposits and pseudoexfoliation, which are other indications for ExPressTM implantation because the shunt is positioned through the obstructed trabecular meshwork. Early placement helps to reduce the effect of topical hypotensive therapy on the conjunctiva. Congenital and juvenile glaucoma are severe forms in patients with long life expectancy. Topical therapy is insufficient and surgery is often the only therapeutic option. Nonpenetrating and minimally penetrating operations should be considered as valid options in classic goniotomy and trabeculotomy failure as an alternative to classic trabeculectomy. However, it must be borne in mind that these are relatively recent techniques with poorly known late complications. Neovascular glaucoma secondary to ocular ischemic pathology (venous occlusion and proliferative diabetic retinopathy) results from neovascular invasion of the iris and camerular angle. Until the advent of anti-VEGF medication and minimally perforating surgery, the treatment of this form of glaucoma was a challenge often crowned with failure. Refractory to topical medical therapy and classic filtration surgery, greatly hindered by the neovascular membrane, cyclodestructive procedures were often the only viable option. After confirmation that intravitreal or sub-Tenon administration of anti-VEGF medication (pegaptanib sodium, ranibizumab and bevacizumab) for the control of choroidal neovascularization also drastically reduced camerular neovessels, thus creating a time window for implant placement surgery without excision of trabecular or iris tissues, the use of anti-VEGF medication was initiated in neovascular glaucoma. The dosing protocol prior to intervention is intravitreal administration of 0.005/0.1 cc for pegaptanib sodium

and ranibizumab and intravitreal or sub-Tenon administration of 0.1/0.3 cc for bevacizumab. The association of the two techniques has completely changed surgical and postoperative prognosis for neovascular glaucoma. However, the intense subscleral and conjunctival postoperative inflammatory response may jeopardize the success of the filtration bleb, making closer monitoring necessary in such cases.

CONTRAINDICATIONS

The main contraindication of this surgical technique is closed angle glaucoma, since shunt placement requires a deep anterior chamber except in combined surgery with lens extraction. Relative contraindications are narrow angles and anterior segment dysgenesis, which require careful prior assessment of the camerular angle.

SURGERY

Anesthesia

In the hands of an experienced surgeon, the surgical technique for placement of an ExPressTM shunt does not require more than local anesthesia. In most cases, subconjunctival or sub-Tenon anesthesia is used, and general anesthesia is reserved for young and noncollaborating patients, and those who request it.4,5

Surgical Technique

Fornix-based conjunctival opening (Fig. 2.2) for scleral exposure with potential cautery of some exposed, bleeding episcleral vessels.

Fig. 2.2: Fornix-based conjunctival opening


Limbal-based scleral flap with 5 × 5 mm, delimited with a 15° blade. Dissection of a flap of approximately one half the scleral thickness using a diamond or mini-crescent blade to reach the grayish corneoscleral transition area (Figs 2.3A and B). In more severe cases, such as neovascular glaucoma, placing a sponge soaked in 0.4% mitomycin C (MMC) on the scleral bed for 3 minutes and then flushing with saline or balanced salt solution (Fig. 2.4). Placing a viscoelastic solution on the cornea protects the epithelium from the adverse effects of antimitotics. Pre-incision of the anterior chamber in the medial portion of the corneoscleral membrane using a 27-gauge needle for the P50 model, which is one of the most often used, and a 25-gauge needle for other models to create a tunnel to facilitate implant insertion. The needle should be oriented at an angle parallel to the limbus and the iris plane, positioning the implant to prevent any contact with the iris or the corneal endothelium (Fig. 2.5). Paracentesis of the anterior chamber using a 15° blade and filling the anterior chamber with a low molecular weight viscoelastic solution to restore the chamber and maintain intraocular pressure. Implant insertion by pressing the central portion of the injector on which the implant is loaded is shown in Figures 2.6A to C.

Figs 2.3A and B: Scleral flap

Suture of scleral flap with monofilament 10/0 is shown in Figure 2.7. Conjunctival suture with 8 or 10/0 absorbable suture, positioned in the two ends of the conjunctival opening, or a continuous running suture, depending on the surgeon’s preference (Fig. 2.8). The chamber is filled with low molecular weight viscoelastic solution through the paracentesis to avoid postoperative hypotony. The volume of viscoelastic solution will depend on the model: models R50 and P50 have a narrower lumen and therefore 1/3 of the chamber should be filled with the solution; for the other models, 2/3 of the chamber should be filled. A properly positioned ExPressTM shunt can be seen in optical coherence tomography—Visante OCT (Fig. 2.9). The gonioscopic image in Figure 2.10 also shows a properly positioned shunt at the medial portion of the trabecular area.

POSTOPERATIVE THERAPY

Postoperative use of an association of antibiotic/steroid eye drops qid in the first 2 weeks, followed by a nonsteroidal anti-inflammatory drug for another 6–8 weeks, is advised.

A B


Fig. 2.4: Sponge with mitomycin C Fig. 2.5: Pre-incision

Fig. 2.5: ???

Figs 2.6A to C: ExPressTM device insertion

A B

C


Fig. 2.7: Scleral sutures

Fig. 2.9: OCT image—implant projection over the iris (1); the aqueous humor subscleral pathway (2); subconjunctival filtration lake (3)

Fig. 2.8: Conjunctival suture

Fig. 2.10: Shunt correctly inserted

COMPLICATIONS

Intraoperative

• Excessively superficial scleral dissection withformation of an excessively thin, poorly resistant scleral flap.

• Improper orientation of the pre-incision tunnel,potentially resulting in shunt misplacement over the iris or touching the corneal endothelium.

Postoperative

Postoperative complications are the same as in any filtration surgery: • Low chamber with hypotony in the early post-

operative period. In more severe cases, it can

be controlled by injecting a viscoelastic solution through paracentesis.

• Hyphema, more frequent in neovascular glaucoma, which resolves in a few days in most cases.

• Choroidal detachment, which can be resolvedwith the usual procedures: cycloplegic drugs, anti-inflammatory drugs, rest and potential surgical decompression in more severe cases.

• Hypertonyasaconsequenceofexcessiveviscoelasticsolution left in the anterior chamber. The pressure may be reduced with partial viscoelastic aspiration using a 25-gauge needle through the paracentesis.

• Fibrosis of the filtration bleb: In cases with aworse prognosis, subconjunctival antimetabolites may be associated intraoperatively (MMC) or


postoperatively (5FU) for prevention, as well as scleral suture lysis, subscleral or subconjunctival needling, or massage. This can be done in any filtration bleb-dependent filtration surgery.

CONCLUSION

In recent years, filtration surgery has been evolving to progressively less invasive techniques in order to achieve tension control with as little structural damage as possible. The so-called “nonperforating” procedures have thus emerged, which combine a relevant hypotensive effect with less invasive surgical techniques and much less ocular globe manipulation, resulting in fewer intra- and postoperative complications. One disadvantage of such techniques is their longer learning curve and lower hypotensive capacity. The ExPressTM mini glaucoma shunt is considered a “minimally perforating intervention” both due to its tiny lumen and because it does not involve tissue excision, similar to nonperforating surgeries. The advantage of the ExPressTM mini glaucoma shunt over nonperforating surgeries is its simple surgical technique.6

Its safety and simplicity allow this surgical alter-native to be considered earlier in patients with a poor response to topical hypertensive drugs.

REFERENCES

1. Dahan E, Mermoud A. The ExPressTM miniature glaucoma implant. In: ShaarawyTM, Sherwood M, Hitchings R, Crowston R (Eds). The Glaucoma Surgical Management, vol. 2. Elsevier; 2009. pp. 157-64.

2. Mermoud A. ExPressTM implant—fast, simple, safe, efficient? Br J Ophthalmol. 2005;89:396-7.

3. Groves N. (2006) Miniature Glaucoma Shunt Comparable to Trabeculectomy. Ophthalmology Times. Advanstar Communications Inc [online]. Available at http://www.highbeam.com/doc/1P3-981045861.html. [Accessed in July, 2012].

4. Dahan E, Carmichael TR. Implantation of miniature glaucoma device under a scleral flap. J Glaucoma. 2005; 14:98-102.

5. Talsma J. Modified implant technique may minimize problems with miniature shunt. Ophthalmology Times. Advanstar Communications Inc; 2005. (online) Available from http://www.highbeam.com/doc/1P3-797832891.html. [Accessed in July, 2012].

6. Wamsley S, Moster MR, Rai S. Results of the use of the ExPressTM miniature glaucoma implant in technically challenging glaucoma cases. Am J Ophthalmol. 2004; 138:1049-51.


INTRODUCTION

Glaucoma drainage devices (GDDs) are intended to divert aqueous humor from the inner eye to an extraocular reservoir. Their history dates back to the early 20th century (Rollet 1907), when several materials and surfaces or drainage locations were tested. Generally showing poor results, these operations often led to infection or inflammation with fistula scarring and/or implant expulsion. In 1969, Molteno introduced the modern concept of drainage implant in which a tube was connected to a plate to improve aqueous humor dispersion. Initially placed next to the limbus, it is often failed due to erosion, exposure and scarring. Later, in 1973, Molteno reviewed his concept and moved the plate to the equatorial area; therefore the current concept arose, in which the devices are composed of a tube (silicone, silastic) and drain aqueous humor from the anterior/posterior chamber to an equatorially located plate or strip in the episcleral space, around which a reservoir is formed. The scarring around the plate influences the final intraocular pressure (IOP) level, resulting in the long-term success of these procedures.

DEVICE CHARACTERISTICS

There are three main characteristics that differentiate posterior drainage devices and may influence device choice.1-3

Presence or Absence of a Flow Restriction Mechanism (Restrictive Versus Nonrestrictive)

In general, valved devices are safer in the early postoperative period because of their better IOP control and lower hypotony incidence. The Ahmed valve and the Krupin device (currently the most widely used) have systems to condition or restrict the flow of aqueous humor inside them. In the Ahmed valve, a silicone membrane folded into leaflets [elastomer (Fig. 3.1)] with a trapezoid shape (Fig. 3.2) creates a Venturi effect which prevents aqueous humor reflux back into the anterior chamber, thus avoiding early hypotony in the postoperative period. The valve system theoretically restricts flow until a pressure of greater than 8–10 mm Hg is exerted upon them.7

Fig. 3.1: Elastomer in the Ahmed valveSource: Br J Ophthalmol 1998;82:1083-9. Perspective Glaucoma drainage devices; past, present and future

Manuela Carvalho

Posterior Drainage Devices 3


In the Krupin valve, the tube is closed at its distal end next to the plate, and it has horizontal and vertical slits which enlarge when the tube expands under increased IOP (>11 mm Hg), to enable a unidirectional flow. For pressure less than 9 mm Hg, the slits will close (second manufacturer). However, experimental tests under physiological conditions seem to show great variability in the restrictive response of these implants.4 The presence of aqueous humor with proinflammatory properties (TGF β2, PG E2) in subconjunctival tissues immediately after surgery seems to induce an increased scarring response that leads to greater wall thickness in the filtration bleb, which in turn leads to a higher long-term failure rate.5

The nonrestrictive devices most often used at present (Molteno and Baerveldt, Figs 3.3 and 3.4) require intraoperative technique variations to avoid early hypotony, which makes the surgery more complex. A two-stage procedure may require maintenance of a provisional hypertensive medical therapy or an association with trabeculectomy. It is imperative to conduct a stricter postoperative follow-up (adjustable, occlusive sutures, intraluminal stent) and these are therefore recommended for more experienced surgeons and collaborating patients. In recent years, technical modifications have been developed for some free flow Baerveldt and Molteno implants that give them some flow-restrictive ability. This is achieved through resistance created by tissue apposition. Although the Bioseal has been discontinued at first for the lack of advantageous clinical results,4 the Molteno 3 shows better practical results.6

Plate Surface Area

Plate sizes have been studied in the past few years to determine the optimal surface area to keep IOP under control. Although the principle of “the larger the better” may be valid, i.e. larger plates permit larger filtration blebs and higher IOP reduction, there seems to be an upper limit.5,6 The current view is that the optimal size is a 170–250 mm single plate, which balances greater efficacy and easier placement6 (Fig. 3.5).

Fig. 3.2: Venturi system in the Ahmed valve

Fig. 3.3: Molteno 3 tube

Fig. 3.4: Baerveldt 350 implant


Composition

Some experimental studies have shown variable inflammatory responses in devices made up of different materials. This varying biocompatibility results in filtration blebs with the capsules of variable thickness, resulting in different filtration rates across their wall.3,7 Two randomized comparative studies7,8 showed that efficacy and safety is higher in silicone versus polypropylene Ahmed valves (Fig. 3.6) of the same size. This suggests that the higher biocompatibility of silicone may be important to surgery success. Device design, texture and rigidity also seem to influence biocompatibility.8

CLASSIC INDICATIONS

Traditional indications for posterior drainage implants include failed trabeculectomy, namely phakic, pseudophakic and aphakic eyes, multiple previous surgeries and neovascular glaucoma. Indications have since expanded to include primary cases of poor surgical prognosis for trabeculectomy.9 In its 2005 Consensus,10 the Association of International Glaucoma Societies (AIGS) divided indications into three categories, discussed below.

Eyes in Which Trabeculectomy With Mitomycin C (MMC), even With Adjunctive Antimetabolite Use, Have a High-Risk of Failure

• PreviousfailedMMCtrabeculectomy• Activeneovascularprocesses

• Active or recurring uveitis • Iridocornealsyndromes• Epithelialingrowthofanteriorchamber• Bullous keratopathy with an indication for

keratoplasty• Associatedvitreoretinalsurgery• Presenceofsiliconeoil• Anteriorsynechiae• Developmental glaucomas associated with angle

anomalies.

Eyes in Which Trabeculectomy is Technically Not Possible or Has a High-Risk of Intraoperative Complications

• Extensiveconjunctivalscarring• Limbalthinning.

Patients in Whom Trabeculectomy With MMC Has a Very High-Risk of Postoperative Complications

• Contact lens wearers• Lidmarginchanges• Previoushistoryofblepharitis• Patientswholiveindirtyand/ordustyenvironments• Riskofsuprachoroidalhemorrhage.

RECENT INDICATIONS

A recent trend is to use GDDs in less refractory cases, thanks to a progressive increase in positive experiences with new materials and a refinement of surgical techniques.11,12 Surveys from the American Glaucoma Society, conducted in 2002 (J Glaucoma 2005) and 2007, confirm this trend.11 The results from the first three years of the TVT Study confirm higher efficacy and fewer complications with the Baerveldt implant versus trabeculectomy with MMC in pseudophakic and/or previously trabeculectomized eyes.12

Fig. 3.5: Baerveldt 250 mm2

Fig. 3.6: Silicone and polypropylene Ahmed valves


Currently, the main barrier to a wider use of tubes in less complicated glaucoma is the lack of knowledge of long-term effects on the corneal endothelium.13

Relative Contraindications14

• Borderlineendothelialcount• Strictpatientcompliancewithpostoperativevisits

is not possible.

PREOPERATIVE ASSESSMENT

Preoperative assessment is crucial to surgery success. Therefore, the following must be taken in consideration: • Conjunctivalstatus,testingconjunctivalmobility

and extent of any scarring. • Irisstudytodetectanyneovascularizationthatmay

predispose to intra- or postoperative hyphemas and indicate previous antiangiogenic therapy.

• Analysis of anterior chamber depth to assesspotential risk of tube contact with the endothelium.

• Gonioscopy to assess the presence and locationof synechiae, neovessels, and angle closure to help choosing which quadrant to use (preferably, the superior temporal quadrant for easier plate placement).

• Lensstatus,becausecombinedsurgeryshouldbeconsidered if cataracts are present.

• Presence of aphakia in a vitrectomized eyewithpotential pars plana tube insertion.

• Presenceofpseudophakiawithpotentialinsertionof a tube in the ciliary sulcus.

• Presenceofvitreoushumorintheanteriorchamber,indicating anterior chamber vitrectomy or potential posterior tube insertion.

• Presenceofsiliconeoil,indicatingdeviceimplantationin an inferior quadrant.

• Predictedassociatedvitreoretinalsurgery(e.g.usageof pars plana clips).

• Predicted futurepenetratingkeratoplasty(betterresults in delayed versus combined surgery).

GENERAL ASSESSMENT

Optimal control should be obtained for the following factors that may affect intra- or postoperative complications: • Preoperative IOP should be as close as possible

to normal, to avoid sudden decompression and to minimize the postoperative hypertensive stage.

• Previousinflammationshouldbereducedasmuchas possible to reduce the postoperative scarring response.

• Control of potential hypertension, therebydecreasing risk of intraoperative bleeding and postoperative hemorrhagic choroid detachment.

• Controlling coagulation and antiaggregation(replacing warfarin with heparin 5 days before, suspending ASA 7 days before, avoiding vitamin supplements containing garlic or vitamin E, which may alter coagulation).

TYPES OF ANESTHESIA

This varies according to the patient’s ocular condition, the cooperation level of the patient and the comfort of the surgeon. In general, peribulbar or retrobulbar block, and sub-Tenon injection or general anesthesia can be used. Topical or intracamerular anesthesia is usually not sufficient because a higher degree of extraocular muscle manipulation is required (especially with larger implants).

SURGICAL TECHNIQUE

This procedure requires attention to every detail and step to improve results and minimize complications. As with all intraocular operations, we should start by preparing the surgical field: • Skindisinfectionwith10%povidone• Eyesurfaceandconjunctivalfornixdisinfectionwith5%povidone

• Sterileplasticdrapes,isolatinglidmargins• Blepharostat,preferablyrigid(Castroviejo),because

it is more resistant to globe mobilization.

Globe Fixation

Globe fixation is essential to ensure a good quadrant exposure. This can be obtained through rectus muscles or corneal traction sutures. In the first case, the muscles need to be isolated and attached with silk sutures (e.g. 5-6/0) for better comfort and exposure, but this will result in a longer operation and requires appropriate anesthesia. Corneal traction sutures (5-8/0, polyglactin, polyester or polypropylene)1,15 are attached faster and therefore require a lower level of anesthesia, although with a slightly lower exposure. In the author’s experience, she prefers 7/0 silk sutures with a spatulated needle since these provide good traction up to the end of the surgery and are easily placed intracorneally.

Conjunctival Flap

The conjunctival flap can be fornix- or limbus-based, although the exposure is facilitated in the fornix approach. In nonavoidable juxtalimbal conjunctival


scarring, an incision can be made 2–3 mm from the limbus1 and a more posterior scleral tunnel can be drawn. The author usually prefers prior hydrodissection of the conjunctival-Tenon plane with BSS or anesthetic, which usually allows subsequent dissection with blunt scissors. In limbus-based dissection, care must be taken that the suture does not coincide with the reservoir location, thus preventing suture dehiscence and reservoir exposure.

Plate Insertion and Fixation

In nonvalved implants, it is easier and therefore recommended to perform technique variants that avoid early hypotony (described below) before plate fixation.7 In restrictive devices, such as the Ahmed valve, the valve must first be primed to confirm that it is in working condition (BSS and 30-gauge cannula). Although the plate and the tube should be inserted in the same quadrant (shorter tube extraocular pathway), different quadrants may have to be used, with sinuous pathways and/or the possible use of tube extensors.1 The edges of larger implants (Baerveldt) have to be inserted under extraocular muscles to prevent ocular and motor imbalance problems.15 For the same reason, double-plate implants have their two reservoirs in two adjacent quadrants and the connection tube is placed under the muscle separating the quadrants. There should be 8–10 mm distance between the anterior edge of the plates and the limbus, or may be in a more posterior location. In small eyes or upper nasal insertions, this distance may be 7–8 mm, because the possibility of a more posterior insertion may cause the posterior reservoir edge to lean on the optic nerve.1 The authors say that 5-9/0 sutures can be used for plate fixation, but these are generally nonabsorbable. The author (of this chapter) uses the same 7/0 silk suture of traction sutures. In a very thin sclera (myopia, buphthalmos), there is a risk of applying transfixative stitches. In these cases, we should choose another fixation place and apply cryotherapy on the perforation site.1,15 The sutures may be perpendicular or parallel to the limbus, although the latter seem to be better at preventing anteroposterior implant movement in the initial stage before capsule formation.

Paracentesis

This is used for the insertion of BSS or viscoelastic material into the anterior chamber (AC), facilitating tube insertion.

Tube Insertion

Before inserting the tube in the AC, the optimal tube length should be ascertained so that the tube penetrates 2–3 mm into the AC (minimum 1.5–2 mm). For this, the tube is placed on the cornea and anterior-bevelled at its proximal end (30–45°) taking into account the corneal curvature (this usually makes it too long, which must be corrected). The tube can be inserted through a small scleral tunnel or juxtalimbal incision; in this case, an additional material is required to cover the tube. A scleral flap as used in trabeculectomy can be performed. A more extensive scleral tunnel can also be made (Carrasco 2010, oral communication, European Glaucoma Society Meeting), but it demands more surgical experience due to the potential of false pathways. Insertion in the AC should be performed with a 23-gauge needle (external diameter 0.65 mm), avoiding touching the iris with the posterior bevel to prevent aqueous humor drainage around the tube, which could result in early hypotony. If larger diameter needles are needed (22- or 21-gauge), the presence of peri-tube drainage should be investigated and solved with a scleral stitch to reduce the incision. If the tube does not slide easily, a viscoelastic material can be used and/or the scleral (not corneal) part of the pathway can be widened slightly, using the needle edges. The tube should be placed parallel to the iris, in the camerular angle, preferably midway between the iris and the cornea, trying to avoid iris obstruction and endothelial contact. If the pathway is not correct, a second one should be created. The faulty pathway should not be corrected to avoid the risk of excessive widening. After insertion, the tube should be fixed to the sclera with 1–2 nonabsorbable stitches (nylon 9/0)15 (5-8/0),1 to improve stabilization and avoid any micromovements that may induce inflammation.

Tube Covering

Usually, if no additional material is available to cover the tube in its extrascleral path, such as pericardium, fascia lata, dura mater, sclera or donor cornea, an autologous scleral flap can be used: • Limbal-baseflap• Lateralflap• Freegraftflap. The above mentioned scleral tunnel technique can also be used. Difficulties may arise from low anterior scleral thickness, the need to use a larger flap than in


trabeculectomy and smaller flap thickness, which may facilitate erosion.

Heterologous Sclera

Advantage• Greaterthicknessfortubeprotection.

Disadvantages• Variablethickness(potentialDellen)• Completesterilizationnotguaranteed• Potentialforimmunereaction.

Dura Mater, Pericardium, Fascia Lata

Advantages• Processingbydehydrationandgammasterilization

prevent HIV and variant Creutzfeldt-Jakob transmission

• Eliminatescellpresence,therebypreventingauto-immune reaction

• Longer-lasting(5years)• Storageatroomtemperature• Easyhandling.

Disadvantages • Logistics• Cost.

Conjunctival Suture

Care should be taken throughout the procedure to avoid conjunctival damage, which may cause difficulties with closure or postoperative dehiscence. In limbal-based flaps, a 7-9/0 running absorbable suture can be used. In fornix-based flaps, the conjunctiva should be brought closer and attached to the limbus with two lateral stitches using 7-8/0 absorbable sutures. Additional stitches may be needed to avoid local dehiscence. If the conjunctiva is much retracted and replacement cannot be made without overtraction, an autologous conjunctival flap,8 or possibly an amniotic membrane graft is recommended to tackle the defect (AmbioDry, Biotissue).

TECHNIQUE VARIANTS1,15

Tube Insertion in the Posterior Chamber

The tube can be inserted in the posterior chamber (ciliary sulcus) in pseudophakic or aphakic patients in cases of: • Previous corneal pathology or keratoplasty with

possible corneal decompensation.

• Angleclosureandverynarrowanteriorchamber,increasing the probability of chronic iris inflammation or corneal decompensation.

The technique is similar, but the tube should be posterior-bevelled to avoid iris incarceration.

Tube Insertion in the Pars Plana

• Inaphakicandfullyvitrectomizedeyes,orinwhichassociated vitreoretinal surgery is foreseen.

• History of predicted keratoplasty: A pars planaclip (universal) or Hofmann elbow is used in the Baerveldt 350 implantation to avoid excessive tube angulation when entering the pars plana (Fig. 3.7).

Technique Variations to Avoid Early Postopera-tive Hypotony (Nonvalved Implants)

Two-Stage Surgery

At first, Molteno proposed an initial plate insertion, leaving the tube in the subconjunctival space and postponing its insertion in the anterior chamber (AC) for 4–6 weeks, by which time the capsule would be formed around the plate. When introducing the tube into the AC, aqueous humor drainage would be controlled by the resistance provided by this fibrous capsule. This procedure has disadvantages: it requires two interventions; it does not immediately control the IOP, requiring continued associated medical therapy or provisional trabeculectomy.

Intraluminal Stent

The tube can be partially closed by inserting a suture in the lumen, usually of nylon or prolene 4 or 5/0. The distal end is left in the subconjunctival space (where it can be fixed) in an adjacent quadrant to that of the

Fig. 3.7: Ahmed valves with pars plana clip


device. Nylon is generally less rigid and provides better postoperative comfort. The suture should be slightly mobilized before conjunctival closure to confirm an easy sliding. After fibrous capsule formation around the reservoir, the suture is removed through a small conjunctival incision, which can be performed under a slit lamp.

Occlusive Sutures

The tube may be fully or partially obstructed with external occlusive sutures, using absorbable on nonabsorbable materials, with sutures between 4 and 8/0, depending on the authors,1,3,15 often polyglactin 7/0. If absorbable sutures are used it is possible to wait for them to dissolve; by then the capsule will have formed around the plate. For nonabsorbable sutures or earlier IOP increase, sutures can be lysed with argon laser or extracted, if they are adjustable. In complete tube occlusion, the tube can be perforated in small slits with a needle or blade in the extracamerular pathway anteriorly to the occlusion (apparently, a 2 mm slit will open under IOP >10 mm Hg). Once the tube is clear, falling pressure inside the tube and the surrounding fibrosis will result in slit closure. Polypropylene or nylon 8-9/0 can also be used to occlude the tube’s proximal end (intracamerular), but it requires subsequent lysis with argon laser.

Combination of Occlusive Sutures and Intraluminal Stent

The advantage of this technique is earlier stent removal. The occlusive suture remains and becomes partial, thereby preventing unexpected hypotony. However, this technique is more complex.

Use of Antiscarring Agents

Antimetabolites (5-fluorouracil or MMC) can be used intraoperatively or postoperatively as subconjunctival injections, with results varying according to the series and authors. Although some retrospective studies confirm a higher efficacy when MMC is applied,1 two recent literature reviews9,17 attribute an evidence level of 1 to a lack of improvement in surgical efficacy when antimetabolites are applied. Some authors report more complications (hypotony, choroidal detachment and conjunctival dehiscence) related to their use. Regarding the postoperative systemic corticoid therapy, the evidence level was also reported as one for its lack of efficacy, although several works describe a response in the transient hypertensive phase (prednisolone, diclofenac, colchicine).15

There are no randomized trials with nonsteroidal anti-inflammatory drugs.9

POSTOPERATIVE COMPLICATIONS

Early Hypotony

Because of excess filtration, it is more common in nonvalvedimplants(with20–30%)thanintheAhmedvalve(8–10%).15 It may lead to:• Athalamia• Endothelialcontact• Cataracts(lenticularcontact)• Choroidaldetachment• Hemorrhagicchoroiddetachment• Maculopathy. In these cases, the anterior chamber should be restored with a viscoelastic material, nonvalved implant sutures should be reinforced and any drainage sclerotomy in extensive and/or prolonged choroidal detachment should be performed.

Transient Hypertensive Phase

As a rule, this stage occurs with every implant and begins between 6 weeks and 8 weeks postoperatively. The IOP increases to 25–30 mm Hg and is of variable duration, decreasing in 2–3 months. It shows absence of visible proximal obstruction. It is more frequent in valved implants, perhaps due to early presence of aqueous humor with proinflammatory properties in subconjunctival tissues.6 Local or potentially systemic hypotensive therapy should be initiated, avoiding prostaglandin analogs, α-adrenergic or miotic drugs, which may increase the inflammatory response.15

Tube- or Plate-Related Complications

Tube Retraction

Due to plate sliding or apparent shortening caused by globe growth, more frequent in children. Re-operation is required to insert a tube extensor.

Anterior Migration

The implant should be relocated to a more posterior site.

Proximal Obstruction • Blood,fibrin• Vitreoushumor(Fig.3.8)• Iris. For blood and fibrin, flushing with BSS in a 30-gauge cannula through paracentesis can be tried. If this does not solve the problem, cleaning with YAG


laser or dissolution with tissue plasminogen activator (10 µg/0.1 mL) can be tried. Take care when using it in the early postoperative period, because it may cause increased bleeding. For vitreous humor or iris, YAG laser or vitrectomy (vitreous humor) can be used.

Late Tube Erosion

Further covering, possibly with conjunctival graft.

Endophthalmitis

It is usually caused by tube erosion, more often in children. Appropriate therapy should be initiated according to the pathogen (Staphylococcus or Streptococcus) with potential implant extraction and insertion of a new one.

Implant Expulsion

It is rare and usually caused by too anterior insertion.

Corneal Complications

It includes edema, endothelial decompensation and band keratopathy. These may result from tube misplacement or excessive mobility, which should be corrected. In situations with prior borderline endothelial count, corneal complications may be due to surgical trauma.

Changes in Extrinsic Ocular Mobility

These are usually due to exuberant blebs or inflammation and fibrosis in adjacent muscles. These may lead to: • Diplopia• Strabismus• AcquiredBrown’ssyndrome(superioroblique).

The resolution involves prisms, strabismus surgery, implant extraction and placement of another smaller implant in another quadrant.

Other Complications of Glaucoma Surgery

• Retinaldetachment• Proliferativevitreoretinopathy• Malignantglaucoma. In each case, the resolution involves posterior vitrectomy.

REMARKS

Trabeculectomy is still the gold standard in glaucoma surgery (European Glaucoma Society—Guidelines 2008), although high efficacy can only be achieved if antimetabolites, in particular MMC, are used. The advances in materials, design and introduction of flow-controlling mechanisms in drainage devices have increased their biocompatibility and safety and thus produced better surgical results. The fear of late trabeculectomy complications with MMC, especially hypotony and endophthalmitis, along with increasingly positive results from newer drainage devices have changed the scene of surgical options in glaucoma, and they are now being used in increasingly less refractory cases. The use of drainage devices in low-risk situations (primary surgery) has been advocated. A multicenter, randomized clinical trial, the PTVT Study is currently under way in the USA. Its purpose is to compare the long-term safety and efficacy of their use against trabeculectomy with MMC, in eyes that have not had previous ocular surgery. In these low risk cases, the author performs nonpenetrating deep sclerectomy, since she finds good results in her clinical practice both in IOP values and low incidence of early and/or late complications. Lack of knowledge about the long-term behavior of the corneal endothelium should prompt us to consider using drainage devices in cases where surgical prognosis is better.

REFERENCES

1. Gutiérrez Díaz E, Montero Rodríguez M. Dispositivos de drenaje para glaucoma. Ediciones Ergon SA. 2002.

2. Burt K, Freeman S, Jeanbart L, et al. (2006) Glaucoma valves. Brown University Biomedical Engineering. [online] Available from http:/biomed.edu/Courses/BI108/2006websites/group02glaucoma/devices.

Fig. 3.8: Proximal obstruction by vitreous humor


3. Salim S. (2010) Glaucoma drainage devices. In: Bruce Shields M (Ed). Eye Wiki. (online) Available from http:/eyewiki.aao.org/Glaucoma_Drainage_Devices.

4. Shetty R, Edney de Filho RM, Ayyala RS, et al. (2008) Glaucoma, Drainage Devices. eMedicine. (online) Available from http://emedicine.medscape.com/article/1208066-overview.

5. Freedman J, Goddard D. Elevated levels of transforming growth factor B and prostaglandin E2 in aqueous humor from patients undergoing filtration surgery for glaucoma. Can J Ophthalmol. 2008;43:370.

6. Freedman J. What is new after 40 years of glaucoma implants. J Glaucoma. 2010;19:504-8.

7. Ishida K, Netland PA, Costa VP, et al. Comparison of polypropylene and silicone Ahmed glaucoma valves. Ophthalmology. 2006;113:1320-6.

8. 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.

9. Minckler DS, Francis BA, Hodapp EA, et al. Aqueous shunts in glaucoma: a report by the American Academy of Ophthalmology. Ophthalmology. 2008;115(6) 1089-98.

10. Weinreb RN, Crowston JG. Glaucoma Surgery. Kugler Publications; 2005.

11. Weinreb RN, Yang-Williams K, Gedde SJ, et al. TVT study results have changed practice patterns. Primary Care Optometry News; April 2009.

12. Gedde SJ, Heuer DK, Parrish RK. Review of results from the tube versus trabeculectomy study. Current Opinion in Ophthalmology. 2019;21:123-8.

13. Barton K, Heuer BK. Modern aqueous shunt implantation: future challenges. Prog Brain Res. 2008;173:263 (Abstract).

14. Liesegang TJ, Skuta GL, Louis B, et al. Basic and clinical science course. Glaucoma. American Academy of Ophthalmology. 2004-2005;201-302.

15. Chen TC. Glaucoma surgery. In: Hampton Roy F, Benjamin L, (Eds). Surgical Techniques in Ophthalmology. Saunders Elsevier; 2008. pp. 55-141.

16. Schwartz KS, Lee RK, Gedde SJ. Glaucoma drainage implants: a critical comparison of types. Curr Opin Ophthalmol. 2006;17(2):181-9.

17. Minckler DS, Vedula SS, Li TJ, et al. Aqueous shunts for glaucoma. Cochrane Database Syst Rev. 2006;(2):CD004918 (Abstract). (online) Available from: http://www.ncbi.nlm.nih.gov/pubmed/16625616

Deep Sclerectomy 23

INTRODUCTION

Contrary to what people might think, the history of nonpenetrating surgery did not start in the 1990s. We need to go as far back as the 1950s1 and early '60s,2 at a time when common practice involved unguarded fistulizing procedures, conducted without a microscope. In 1964, Krasnov3 was the first to report a procedure called sinusotomy, which consisted of excising an in-depth scleral band down to Schlemm’s canal over 120°. This did not penetrate the anterior chamber and covered the excised area with conjunctiva. When Krasnov3 could not drain the aqueous humor through the trabeculum and Schlemm’s canal inner wall, he entered the anterior chamber to perform peripheral iridectomy, creating an unguarded filtering procedure (the usual procedure at the time). During the '80s, using the microscope and after the Cairns technique became popular, Fyodorov4 and Zimmerman5 performed sinusotomy with a guarding superficial flap, known as nonpenetrating trabeculectomy. In the '90s6-8 several surgeons modified this technique: Schlemm’s canal was cannulated and dilated with viscoelastic material, a trabeculodescemetic window was created; peeling of the inner wall of Schlemm’s canal was created; and an implant was applied to the scleral bed to create a passage between scleral bed and subconjunctival space. That is how deep sclerectomy (DS) and viscocanalostomy were born. These are two different surgical procedures with distinctive purposes and mechanisms. This chapter will only address deep sclerectomy. Viscocanalostomy is not a filtrating procedure, but an embryonic version of canaloplasty, which is covered in a separate chapter.

Deep sclerectomy is a filtration surgery. The advantage of deep sclerectomy over trabeculectomy is that it lowers intraocular pressure (IOP) intraoperatively and progressively through a controlled flow of aqueous humor between the anterior chamber and the subconjunctival space. This surgical technique does not involve opening the anterior chamber, abrupt aqueous humor outflow or loss of depth in the anterior chamber. Progressive, controlled flow of aqueous humor is achieved by opening Schlemm’s canal, creating a trabeculodescemetic window and peeling of the inner wall of Schlemm’s canal, which is often associated with microperforations in the juxtacanalicular meshwork. Upon reception of a deep scleral flap and closure of the superficial scleral flap, an intrascleral space is created that functions as a reservoir for aqueous humor. This space is usually maintained by inserting an absorbable or nonabsorbable implant (Figs 4.1A and B). The main drainage mechanism is the outflow of aqueous humor from the anterior chamber to the intrascleral space, and from here to the subconjunctival space. In addition, there are other adjuvant mechanisms that contribute to lowering the IOP. First, an increase in the uveoscleral drainage pathway, achieved with deep scleral flap dissection, leaving the ciliary body/choroid visible through the remaining sclera. This facilitates absorption of the aqueous humor in the suprachoroidal space. The developers of the Esnoper® nonabsorbable implant prescribe insertion of its distal portion in a suprachoroidal pocket, based on this principle of facilitating uveoscleral flow. Second, an increase in the conventional drainage pathway by creating


Deep Sclerectomy 4


an intrascleral lake which provides direct access to Schlemm’s canal and the collecting ducts. Bearing the latter mechanism in mind, some surgeons (including myself) associate deep sclerectomy with Schlemm’s canal dilation using viscoelastic material. In fact, from an anatomical as well as a histological point of view, Schlemm’s canal is not a mere endothelial tube. Within it are collagen pillars which begin in the posterior wall and continue to the collecting ducts (this is often seen during deep flap dissection). In more advanced glaucoma, decreased aqueous humor flow leads to reduced collagen pillar elasticity, Schlemm’s canal collapse and closure of some collecting ducts. Insertion of viscoelastic material expands Schlemm’s canal and collecting ducts, and it also ruptures more fibrous pillars. This maneuver also causes microperforations in the inner wall of the canal, facilitating aqueous humor outflow from the anterior chamber, and disruptions of Schlemm’s canal posterior wall, increasing drainage through the uveoscleral pathway. It has been described that dilation and disruption in enucleated eye models9 may extend for approximately 6 mm beyond the viscoelastic injection site. The combination of these drainage mechanisms makes filtration blebs flatter, which causes fewer changes to the lacrimal film and less discomfort for the patient (Table 4.1).

INDICATIONS

Indications for deep sclerectomy follow generic indications for glaucoma surgery: medically uncontrolled glaucomas, glaucoma or ocular hypertension intolerant to medical therapy and therapy noncompliance. Medically uncontrolled glaucoma is defined as the

Table 4.1: Deep sclerectomy—advantages and mechanisms

Advantages • Minimallyinvasive,nonpenetrating surgery

• Doesnotpenetratetheanteriorchamber

• Controlled aqueous humoroutflow

• Fewerintraandpostoperativecomplications

• Fasterrecovery

• Flatterblebs

Main drainage mechanism • Subconjunctivalpathway

Adjuvant mechanisms • Uveoscleralpathway

• Conventionalpathway

Fig. 4.1A: Filtration bleb 1 year after surgery Fig. 4.1B: Intrascleral lake, 1 year after DS with aquaflow implantSource: iUltrasound (iScience Interventional)

presence of disease progression signs, as shown by perimetry or focal or general increase in the cup/disk ratio.

Strictu Sensu

This technique should only be performed in cases with camerular angle with at least Shaffer grade 3. It is indicated for: primary open-angle glaucoma; pseudoexfoliative glaucoma; pigmentary glaucoma; cortisone glaucoma; glaucoma in pseudophakic or phakic eyes; other open-angle secondary glaucomas. Since deep sclerectomy is much less proinflammatory and does not cause sudden decompression, it is preferentially indicated in glaucoma secondary to uveitis (without peripheral anterior synechiae or iris bombé), glaucoma in high myopia, advanced glaucoma and glaucoma associated with Sturge-Weber syndrome or nanophthalmos (Table 4.2).

Deep Sclerectomy 25

Relative Contraindications

Narrow-angle glaucoma or plateau iris: these are not contraindications in the absence of peripheral anterior synechiae and if associated with phacoemulsification; glaucoma secondary to angle anomalies: iridocorneal endothelial syndrome (ICE), congenital and juvenile (Table 4.2).

Absolute Contraindications

Absolute contraindications for deep sclerectomy are: absolute glaucoma; angle recession; neovascular glaucoma; chronic closed-angle glaucoma (Table 4.2).

PATIENT’S ASSESSMENT

Further to general ophthalmological assessment, it is crucial to assess eye surgery history in patients who are candidates for deep sclerectomy. If there is a history of cataract surgery we must find out whether it was

performed by phacoemulsification or extracapsular extraction, whether an intraocular lens was inserted, and whether the surgery had complications. In patients with a history of trabeculoplasty, the location on trabeculum should be determined, plus whether there were any repetitions and which type of trabeculoplasty was performed: argon, diode or selective laser trabeculoplasty. Glaucoma characterization is the key. This requires careful anterior segment analysis, detailed gonioscopy description and, if possible, anterior segment optical coherence tomography [OCT (Figs 4.2A and B)], 80 MHz ultrasound or ultrasound biomicroscopy (UBM). As it is a nonpenetrating surgery, success requires that eyes with or which may favor peripheral anterior synechiae be excluded.

SURGICAL TECHNIQUE

Preoperative preparation includes application of one drop of 2% pilocarpine, 30 minutes before surgery. The author prefers initiating prophylaxis for endophthalmitis, 3 days before surgery with broad-spectrum antibiotic eye drops, combined with topical nonsteroidal anti-inflammatory eye drops. Before the surgery itself, lateral paracentesis with a 15° blade should be performed. This can be used in several surgery stages. Paracentesis can also be done after creating a superficial scleral flap, immediately before entering Schlemm’s canal. Magnification should be adapted to control each step. The procedure is generally performed at 12 o’clock. Operative field exposure is essential for quick, uncomplicated surgery. When adequate exposure cannot be obtained, the author advises passing a W-shaped suture at 10 o’clock and 2 o’clock using a 10/0 polyamide or 8/0 polyglactin 910 suture. This technique allows you to turn the eye inferiorly, and to hold the scleral flap during part of the surgery, allowing the assistant surgeon to perform other tasks (Fig. 4.3).

Table 4.2: Deep sclerectomy—indications and contraindications

Indications • Primaryopenangleglaucoma

• Secondaryopenangleglaucoma

• Glaucomainhighmyopia

• Advancedglaucoma

• Glaucoma associated withSturgeWebersyndrome

• Glaucomainnanophthalmos

Relative contraindications • Narrowangle glaucoma orplateau iris

• Glaucomasecondarytoangleanomalies:ICE,congenitalandjuvenile

Absolute contraindications • Absoluteglaucoma

• Anglerecession


• Chronicclosedangleglaucoma

Fig. 4.2B: Open-angle, without contraindication for deep sclerectomySource: SL-OCT (Heidelberg Engineering)

Fig. 4.2A: Narrow-angle, contraindicated for sclerectomySource: SL-OCT (Heidelberg Engineering)


To avoid perforation, the membrane can be gently detached using a microsponge or spatula. After creating a descemetic window, deep scleral flap excision should be performed with Galand scissors (Huco, Switzerland, 4.2350). Peeling of the inner wall of Schlemm’s canal is performed with Mermoud forceps (Huco, Switzerland, 3.4475) (Fig. 4.4F). As mentioned, the author always dilates Schlemm’s canal using a Grieshaber cannula and viscoelastic material. To avoid collapse of superficial scleral flap and fibrosis of the newly created intrascleral space, an implant should be inserted. At present, three implants are available: one absorbable and two nonabsorbable. The absorbable implant is the oldest and the first to be marketed, and its application is the simplest of all three. This implant is called AquaFlow® (Staar,

Fig. 4.3: W-shaped corneal suture

Surgery should begin by opening the conjunctiva and Tenon’s capsule at the limbus for approximately 8–10 mm to expose the sclera. In the author’s opinion, it is worth performing tenectomy in cases of thick Tenon’s capsules (Fig. 4.4A). The superficial sclerectomy location should be free from collecting ducts, if possible. To keep the work area as dry as possible, vessel cauterization can be performed using thermal cautery or diathermy. The scleral area to be dissected should be approximately 5 × 5 mm (Fig. 4.4B). The area can have different shapes: quadrangular, triangular or parabolic. Scleral areas can be marked with a compass and 15° blade or using customized surgical instruments. The thickness of the superficial scleral flap dissection should be approximately one-third of total scleral thickness and extend 1 mm into the clear cornea (Fig. 4.4C). For scleral flap dissection, the author suggests using a 1.25 mm, mini-crescent angled knife (Sharpoint, PA, USA). A deeper scleral flap can then be drawn over the previous flap’s bed, approximately 1 mm from the edge. The scleral flap should be dissected with 90° edges and very close to the ciliary body/choroid, slowly extending to the anterior globe until it reaches Schlemm’s canal (Fig. 4.4D). If the eye is very tense some aqueous humor should be removed by paracentesis immediately before reaching Schlemm’s canal. This will prevent perforation of the inner wall of Schlemm’s canal or the descemetic membrane. Dissection should then open Schlemm’s canal and create a trabeculodescemetic window. A window can be obtained by proceeding with deep scleral flap dissection as far as Descemet’s membrane in the clear cornea. This space should be twice as large as the segment encompassing Schlemm’s canal (Fig. 4.4E).

Fig. 4.4A: Tenectomy

Fig. 4.4B: Delineation of superficial scleral flap

Deep Sclerectomy 27

Fig. 4.4C: Scleral flap up to approximately 0.5–1 mm into clear cornea

Fig. 4.4D: Deep scleral flap with visualization of ciliary body through the remaining sclera

Fig. 4.4E: Cutting of deep scleral flap Fig. 4.4F: Unroofing of Schlemm’s canal

Surgical AG Nidau, Switzerland) and consists of a highly purified, dehydrated porcine collagen cylinder (4 × 1 × 1 mm). The implant should be placed radially at the center of a dissected scleral bed and secured with a 10/0 polyamide suture. The implant’s anterior area should rest on the trabeculodescemetic window (Figs 4.5A and B). The Esnoper® (AJL Ophthalmics SA, Miñano, Alava, Spain) is a nonabsorbable acrylic implant of 2-hydroxyethylmethacrylate (HEMA, 2.85 × 3 × 1.4 mm), with sulci at its anterior side to facilitate aqueous humor drainage, as well as two orifices: an anterior orifice to facilitate aqueous humor outflow and a posterior orifice to pass a suture wire for scleral

attachment. Several issues should be considered in its application: first, a suprachoroid pocket should be created in the upper posterior scleral bed (which should be deep enough for the implant’s anterior side not to touch the trabeculodescemetic window) (Figs 4.6A and B); second, it is advisable to secure the implant to scleral bed edges with 10/0 polyamide sutures; third, the implant should be positioned and only then should the suture be passed on one of lateral edges of the scleral bed (at the level of the suture orifice), then passed through the orifice, and finally passed into the edge of the other side of the scleral bed (the suture should be horizontal, parallel to the limbus). Finally, a double knot is tied.


Fig. 4.5A: AquaFlow® implant Fig. 4.5B: 24-hour implant image obtained with iUltrasoundSource: iScience Interventional

Fig. 4.6A: Esnoper® implant Fig. 4.6B: 24-hour implant image obtained with iUltrasoundSource: iScience Interventional

The T-Flux®NV (Carl Zeiss Meditec, Germany) is another hydrophilic acrylic (Poly-Megma) non-absorbable implant. T-Flux is T-shaped with a 4 mm arm, 3.4 mm body and 0.1–0.3 mm thick. The arms of the T should be inserted at the level of Schlemm’s canal and should be secured to scleral bed edges with a 10/0 polyamide suture, which is passed through the central orifice to stabilize the implant (Figs 4.7A and B). Some surgeons create a suprachoroid pocket in the scleral bed and insert the T-Flux body there and no suture is necessary. The superficial flap is closed with two diagonal absorbable suture stitches (8/0 polyglactin 910) at the corner of posterior flap edges. The purpose is to immobilize the flap and not create a watertight closure.

After closing the superficial scleral flap, viscoelastic material can be positioned on the scleral bed to prevent sudden decompression and to inhibit inflammation. Watertight conjunctival closure can be performed with the same suture (Figs 4.8A and B). For endophthalmitis prophylaxis, the author suggests a subconjunctival cefazolin injection, followed by broad-spectrum antibiotic eye drop instillation, 5 times a day for 15 days. As an anti-inflammatory and antifibrotic treatment, the author usually uses a subconjunctival betamethasone injection perioperatively, followed by prednisolone and flurbiprofen instillation 5 times a day for 1 month after surgery. For prophylaxis of peripheral anterior synechiae, the author usually instils one drop of 2% pilocarpine at the end of the surgery.

Deep Sclerectomy 29

Fig. 4.7A: T-Flux® NV implant Fig. 4.7B: 24-hour implant image obtained with iUltrasoundSource: iScience Interventional

Fig. 4.8A: Superficial scleral flap after closure Fig. 4.8B: Filtration bleb 8 days after surgery

In combined surgery, involving deep sclerectomy and phacoemulsification with intraocular lens insertion, the procedure should start with sclerectomy, creating superficial and deep scleral flaps until Schlemm’s canal is accessed. This should not be opened and no trabeculodescemetic window should be created (scleral flap dissection is facilitated by higher eye tonicity, but opening the canal and creating a descemetic window before phacoemulsification may lead to its rupture). Cataract surgery is performed and afterwards the sclerectomy is resumed. Some surgeons prefer to perform cataract surgery first and afterwards the deep sclerectomy. In the immediate and late postoperative periods, goniopuncture is sometimes required (see indications

below). Like needling in trabeculectomy or YAG capsulotomy in cataract surgery, goniopuncture is an adjuvant procedure to deep sclerectomy. It is an effective and safe procedure. Goniopuncture can be performed in the absence of goniosynechiae to increase aqueous humor flow to the intrascleral bed. Goniopuncture is performed with the help of a goniolens and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Two to five impacts should be performed at the level of the semitransparent trabeculodescemetic window, with a power of 4–7 mJ. To increase visualization of the camerular angle, instilling 2% pilocarpine 30 minutes prior to goniopuncture is recommended. NSAID eye drops should be instilled for 5 days after goniopuncture.


DIFFICULTIES/COMPLICATIONS AND THEIR INTRAOPERATIVE RESOLUTION

Depth of Deep Scleral Flap

As in all surgical techniques, difficulties and complications occur less often as the learning curve develops. One of the initial difficulties is to determine the ideal depth for the deep scleral flap. When a deep scleral flap is delineated with the 15° blade, we must be able to see through the remaining sclera to the choroid, and dissect a little with the blade before changing to the mini-crescent blade. The same plane should always be kept and if the flap’s lateral edges have to be freed, the blade should be vertically positioned to follow upward movements. If when the transition line between the sclera and the trabecular meshwork is reached the plane is superficial to Schlemm’s canal, a new flap should be initiated. A deeper flap should then be made at the flap’s distal portion (avoiding a deeper cut next to the trabecular meshwork). The deep scleral flap should only be excised after finding and opening the Schlemm’s canal and creating a descemetic window. But if the deep scleral flap is too deep and exposes the choroid/ciliary body (choroidal/ciliary body hernia), a more superficial scleral plane should be found away from that area to avoid making the hernia bigger. In a protuberant hernia, the IOP should be decreased by paracentesis. Once a new plane has been found the surgery can proceed.

Perforation of Trabeculodescemetic Window

Opening Schlemm’s canal, creating a trabeculo-descemetic membrane, peeling of the inner wall of Schlemm’s canal and cutting a deep scleral flap are

the most sensitive moments of the surgical technique. Perforation may occur at any of these stages. If it does, the action will depend on perforation size, presence of prolapse of the iris or loss of anterior chamber. In a microperforation, acetylcholine chloride (Miochol®) should be injected in the anterior chamber and the procedure continued. In a macroperforation with loss of anterior chamber but no prolapse of the iris, administer a miotic drug, air bubble or viscoelastic material in the anterior chamber, perform peripheral iridectomy (to avoid postoperative iris incarceration), and then proceed with the surgery. In a macroperforation with prolapse of the iris, peripheral iridectomy should be performed, administering a miotic drug, air bubble or viscoelastic material in the anterior chamber. The surgery can then proceed if we are sure the wound is tightly closed. In a nonlinear perforation with anterior chamber shape loss, even after air bubble or viscoelastic application, the surgery must be finished by ab externo trabeculectomy (Flow chart 4.1).

IMMEDIATE POSTOPERATIVE COMPLICATIONS AND RESOLUTION OF COMPLICATIONS (1–10 DAYS)10

Seidel

In a small, nonhypotonic Seidel or anterior chamber loss, steroid anti-inflammatory eye drops should be initiated 2–3 days later. Larger or hypotonic Seidel or with anterior chamber loss warrants surgical review.

InflammationIt is considered low and resolves after 1 week.

Flow chart 4.1: Perforation of trabeculodescemetic window

Deep Sclerectomy 31

Hypotony

Fifty percent of patients have hypotony on the first day after surgery (average 5 mm Hg) with well-formed anterior chamber, and in the absence of membrane rupture or Seidel; this is a good sign of trabeculo-descemetic window competence. Within 1 week, tension values increase and no additional therapy is needed.

High Intraocular Pressure

This may result from:• Nonopening of Schlemm’s canal, insufficient

dissection or insufficient peeling. Goniopuncture should be performed in such cases, but if this proves inadequate, surgical review must be carried out.

• Iris incarcerationwithin the trabeculodescemeticwindow caused by neglected intraoperative or postoperative rupture due to Valsalva’s maneuver. Surgery should be reviewed and peripheral iridectomy performed (Fig. 4.9).

• Formation of peripheral anterior synechiae dueto sclerectomy in narrow- or closed-angle eyes. If recent, they may respond to 2% pilocarpine or Nd:YAG laser synechiolysis, but if they do not respond surgical review with peripheral iridectomy must be performed.

• Presence of viscoelasticmaterial in the anteriorchamber in a combined procedure: hypotensive treatment.


This is rare in nonpenetrating procedures (5% versus 20% trabeculectomy). If small, there is no specific therapy; if large, consider cycloplegia with atropine and anti-inflammatory therapy reinforcement.

Low Anterior Chamber

Search for Seidel or iris incarceration within the trabeculodescemetic window and act accordingly.

Hematic Tyndall/Hyphema

Extremely rare.

Descemet’s Membrane Detachment

Rare and always associated with cannula dilation.

Reduced Visual Acuity

There may be temporary vision loss which will recover in approximately 1–3 months. One cause may be induced astigmatism (this may be avoided if superficial scleral flap suture is performed after filling the anterior chamber and with an absorbable suture).

LATE POSTOPERATIVE COMPLICATIONS AND RESOLUTION OF COMPLICATIONS (2–5 WEEKS)

Increased Intraocular Pressure

This may result from:• Collapsed scleral lake or fibrosis of trabeculo-

descemetic window. In this case, goniopuncture should be performed. Trabeculodescemetic window fibrosis may occur with time (average 29 months), which is a cause of failure. Goniopuncture is indicated in this situation. This procedure may be repeated, if needed.

• Formationofperipheralanteriorsynechiaeatthetrabeculodescemetic window secondary to micro- or macroperforation with iris incarceration. If recent, the iris could be released with 2% pilocarpine or Nd:YAG laser synechiolysis, but if it does not respond surgical review with peripheral iridectomy must be performed.

• Traumatic rupture of the trabeculodescemeticmembrane with iris incarceration: surgical review with peripheral iridectomy must be performed.

• Fibrosisandencapsulationofthefiltrationbleb:Theprocedure is similar to ab externo trabeculectomy.

Blebitis

The procedure is similar to ab externo trabeculectomy.

Fig. 4.9: Peripheral anterior synechia juxtaposed on the trabeculo-descemetic windowSource: iUltrasound (iScience Interventional)


REMARKS

When comparing different surgical steps in ab externo trabeculectomy and deep sclerectomy, we realize why both techniques are effective, why a nonpenetrating surgery involves fewer peri- and postoperative complications and why they share some causes of failure. Whereas opening the anterior chamber and excising the trabeculum cause a sudden aqueous humor outflow in trabeculectomy, creating a trabeculodescemetic window and peeling the inner wall of Schlemm’s canal in deep sclerectomy reduce resistance to the progressive and constant outflow of aqueous humor, without serious decompression. This prevents anterior chamber loss, hypotony and choroidal detachment, both intraoperatively and immediately after surgery. In tests on enucleated human eyes, it has been reported that IOP decrease is 5.5 times faster with ab externo trabeculectomy than with deep sclerectomy.11 Conservation of anterior chamber depth, reduced hypotony, and choroidal detachment lead to minor postoperative intraocular inflammation episodes. This, associated with no postoperative atropine administration, results in a much smoother postoperative period, with much faster visual recovery and return to active life. As they are minor, inflammatory events also decrease fibrosis mechanisms, and in glaucoma secondary to uveitis, surgical efficacy and postoperative recovery is dramatically increased. Another important aspect is that it is less cataractogenic. The Advanced Glaucoma Intervention Trial12 estimates that cataract formation in 78% of first trabeculectomy occurs within 5 years. Furthermore, the cataract risk doubles in the presence of low anterior chamber and postoperative inflammation. Shaarawy et al.13 report that after 64 months, senile cataract progressed in 25% of the patients undergoing deep sclerectomy. Egrilmez et al.14 compared refractory changes induced with different filtration procedures and concluded that although surgical areas in nonpenetrating techniques (deep sclerectomy and viscocanalostomy) were larger than in trabeculectomy, they induced less astigmatism both in the immediate postoperative period, and after 6 months. Even using mitomycin C, the filtering bleb looks flatter, is esthetically more pleasing and, as it causes fewer changes in the tear film, it reduces the discomfort patients often complain of. Finally, the author cannot end this chapter without mentioning a work published by Bissing et al.,15 who carried out a 10-year assessment of the first 105 eyes to undergo deep sclerectomy with collagen implants

performed by André Mermoud. It was shown that the 10-year qualified success was 89%, with a decrease between preoperative average IOP values of 26.8 ± 7.7 mm Hg to a postoperative average IOP of 12.2 ± 4.7 mm Hg. Corrected visual acuity decreased from 0.71 ± 0.33 to 0.53 ± 0.25 in the first postoperative day. Visual acuity recovered after one month and was maintained for 10 years (cataract surgery rate 40% after 10 years). During this time (from month 1 to month 119), goniopuncture was performed in 61 eyes, with an average of 29 months between sclerectomy and goniopuncture. No serious complications were reported.

REFERENCES

1. Epstein E. Fibrosing response to aqueous; its relation to glaucoma. Br J Ophthalmol. 1959;43:641-7.

2. Krasnov MM. Externalization of Schlemm’s canal (sinusotomy) in glaucoma. Br J Ophthalmol. 1968;52: 157-61.

3. Krasnov MM. Sinusotomy in glaucoma. Vestn Oftalmol. 1964;77:37-41.

4. Fyodorov SN, Ioffe DI, Ronkina TI. Deep sclerectomy: technique and mechanism of a new antiglaucomatous procedure. Glaucoma. 1984;6:281-3.

5. Zimmerman TJ, Kooner KS, Ford VJ, et al. Trabeculectomy vs. nonpenetrating trabeculectomy: a retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg. 1984;15:734-40.

6. Koslov VI, Bagrov SN, Anisimova SY, et al. Nonpenetrating deep sclerectomy with collagen Oftalmokhirurgia. 1990;3:44-6.

7. Arenas E. Trabeculectomy ab-externo. Highlights of Ophthalmology. 1991;19:59-66.

8. Stegmann R. Trabeculo-viscotomy. Highlights of Ophthalmology. 1993;1:218-9.

9. Wild GL, Kent AR, Peng Q. Dilation of Schlemm’s canal in viscocanalostomy: comparison of 2 viscoelastic substances. J Cataract Refract Surg. 2001;27:1294-7.

10. Mendrinos E, Mermound A, Shaarawy T. Nonpenetrating Glaucoma Surgery. Survey of Ophthalmology. 2008;53:592-630.

11. Vaudaux J, Uffer S, Mermoud A. Aquous dynamics after deep sclerectomy: in vitro study. Ophthalmic Pract. 1999;16:204-9.

12. AIGS Investigators: The advanced glaucoma intervention study: 8. risk of cataract formation after trabeculectomy. Arch Ophthalmol. 2001;119:1771-9.

13. Shaarawy T, Flammer J, Smits G, et al. Low first postoperative day intra-ocular pressure as a positive prognostic indicator in deep sclerectomy. Br J Ophthalmol. 2004;88:658-61.

14. Egrilmez S, Ates H, Nalcaci S, et al. Surgically induced corneal refractive change following glaucoma surgery: nonpenetrating trabecular surgeries versus trabeculectomy. J Cataract Refract Surg. 2004;30:1232-9.

15. Bissing A, Rivier D, Zninetti M, et al. Ten years follow-up after deep sclerectomy with collagen implant. J Glaucoma. 2008;17:680-6.

Gonioscopic Surgery 33

INTRODUCTION

Apparently, von Graefe’s initial concept for his iridectomy was based on the premise that iridectomy would lower intraocular pressure by reducing the exudation of fluid produced by the iris. Moreover, it seems that in the late 19th century, de Wecker may have been the first to challenge the theory. He may have realized that the surgical intervention caused inadvertent, unforeseen filtration through the surgical incision, and this, in fact, brought about ocular tone reduction. Therefore, for more than a century creating a pathway for aqueous humor to flow from the anterior chamber to subconjunctival space has been the leitmotiv of all glaucoma surgery.1,2 All? Well, like Goscinny and Uderzo’s small Gaul village, one technique has held out against the transconjunctival hegemony: goniotomy. Although limited to surgical therapy of congenital glaucoma, this technique is the only classic ab interno access technique, and combines this with a surgical approach concept to which the current chapter is devoted. The surgical choice of nonconjunctival access and ultimately of not producing a subconjunctival fistulizing pathway should, in principle, be a far more logical concept. In fact, fistulizing surgeries are a biological contradiction: on one hand the purpose is to create a wound, in the hope; on the other hand, it will never fully scar. Proliferation of scleral and subconjunctival fibroblasts and their natural scarring function through collagen and fibronectin synthesis is one of the main obstacles to the efficacy of filtration surgery.

The juxtacanalicular trabeculum and the inner wall of Schlemm’s canal are the main source of resistance to aqueous humor drainage. Bahler, Zhou et al. have introduced the experimental concept of creating a duct through the trabeculum to Schlemm’s canal and have studied the in vitro effect of this trabecular bypass on facilitation of aqueous humor drainage.3 These experiments led to the creation of a microimplant, which is already available in the market. The first experiences with its use have been reported in a few preliminary studies. This microstent—Glaukos iStent®—is an L-shaped microtube whose penetrating end is beveled while the opposite end, which will remain in the anterior chamber, is circular. The device’s striated cylindrical body helps stabilize the inner duct and is made of heparinized surgical titanium. Only 1 mm long, and having a maximum inner diameter of 0.25 mm, it is the smallest medical device ever implanted in the human body (Fig. 5.1). The stent is inserted in the anterior chamber via the transcorneal route, with gonioscopic viewing, a prior important requirement is sound experience in gonioscopy and a reasonable command of surgical gonioscopy direct lenses. A temporal surgical approach is used for nasal placement: at 3–4 o’clock for the right eye, at 9–8 o’clock for the left eye. The stent end should always be pointing downwards: there are therefore two stent versions, one for each eye. It is important that the patient is properly positioned (head facing away from incision), and that the microscope head is slanted so that the camerular angle is exposed.

A Rodrigues Figueiredo

5Gonioscopic Surgery: Trabecular Micro-

Bypass Stent Implantation


The incision in clear cornea requires approximately 3 mm. If associated with phacoemulsification, the latter’s incisions are used as a basis. Pharmacological miosis should subsequently be provoked and the chamber filled with viscoelastic material. Then a goniolens is inserted. One ought to avoid excessive pressure on the goniolens, because corneal folds will form that hinder angle visualization. This is a crucial step: without clear visualization of trabecular structure, it is not worth activating the iStent for placement. The applicator holding the stent is then inserted through the corneal incision, crossing the entire anterior chamber up to the nasal angle. Slightly pressing the

stent edge on the trabeculum may help to position the applicator and give some guidance on proper stent movement. Basically, the technique is similar to vessel puncture: there should be no resistance when the bevel penetrates the canal. At this point, there is usually slight bleeding which indicates that the stent has been properly positioned in the canal (Figs 5.2 and 5.3). The whole stent body should be inserted. Only then the stent is released from the applicator by opening its gripper system (Fig. 5.4). Flushing this, usually tiny hyphema (Fig. 5.5) and viscoelastic material, followed by sealing the corneal incisions, complete the procedure.

Fig. 5.1: Microstent—Glaukos iStent® Fig. 5.2: iStent properly positioned in the canal

Fig. 5.3: iStent properly positioned in the canal Fig. 5.4: iStent completely inserted

Gonioscopic Surgery 35

The surgery can be performed under local anesthesia and associated therapy merely consists of postoperative topical antibiotic therapy (fluoroquinolone); if this surgery is combined with phacoemulsification, the latter’s routine procedures already include therapy. Intraoperative complications are scarce. The most common is loss of trabecular area viewing due to bleeding caused by a failed attempt at stent insertion. Good assessment of this surgical step is recommended, and if possible, do not retreat once the channeling process has been started. Similarly, a flaccid or atrophic iris may complicate the surgical procedure by hindering stent advancement or causing bleeding by inadvertent bevel contact (this did once prevent us from inserting a stent). Postoperative complications are also uncommon: in our experience, only one case of iris obstruction of the stent bore occurred, which was successfully solved with argon laser. However, incorrect stent positioning and failure due to potential obstruction have been described. Indications for this gonioscopic surgery may be limited in the context of the total population of surgical patients. In fact, with its relatively simple, minimally invasive and rarely complicated procedure, a lower relative efficacy is perhaps its main limitation. Fully excluded from this surgical indication are patients with corneal opacity and patients with synechiae of the angle at the intervention area. Patients who have undergone prior filtration surgery, viscocanalostomy or cyclophotocoagulation should also be excluded. Patients with a history of laser trabeculoplasty and those with a history of long

progression, or suspicion of Schlemm’s canal changes or collapse should also avoid this surgery. Favorable indications are associated with phaco-emulsification, patients at risk of postoperative uncontrolled pressure; patients with maximum medical therapy, where drug intolerance is expected; fear that a standard, more invasive surgery may increase postoperative complications, such as in preterminal uncontrolled glaucoma. For data on efficacy and safety of gonioscopic surgery,4,5 the author refers to the multicenter study presented at the American Society of Cataract and Refractive Surgery on the 12-month progression data in 42 patients. The mean IOP was 21.7 ± 3.9 mm Hg. At 12 months, there was a reduction of 4.4 ± 4.5 mm Hg, i.e. 18.3% (p < 0.001). Drug number fell from 1.6 ± 0.8 to 0.4 ± 0.6, and half of the patients achieved pressures lower than 18 mm Hg without medication. In our experience, gonioscopic therapy had included 5 patients with more than 6 months follow-up (until 2011): four primary open-angle glaucoma cases and one pseudoexfoliative glaucoma case. Four procedures were associated with phacoemulsification and one was conducted in a pseudophakic patient. Mean intraocular pressure (IOP) decreased from 20.8 mm Hg to 17.1 mm Hg (17.8%) and drug number fell from 3.75 to 2.5. Only one patient achieved IOP below 18 mm Hg without additional therapy. As with other stent and valved devices for the surgical therapy of glaucoma, initial versions are always open to improvement. In fact, stent modifications have been under development since 2010 and a new version is expected on the market soon. It has a new design where one end is conical rather than beveled. The cylinder body now has lateral orifices, but the main difference seems to lie in the placement technique; since this device will not be intended to canalize Schlemm’s canal, but to be “ejected” into the canal and be propelled across the trabeculum by an ejector. For this, an area has been designed on the device to secure it in the canal after insertion. Furthermore, other stents can be placed internally with the aid of surgical gonioscopy: the suprachoroidal microstents. Inserted between the scleral spur and the ciliary body, they create a pathway between the anterior chamber and the suprachoroidal space, stimulating uveoscleral drainage. Two stents with similar characteristics are currently being studied. They consist of a perforated, microtubular structure approximately 6 mm in length,

Fig. 5.5: Tiny hyphema


with several surface stabilization rings. The stent is inserted under gonioscopic control by creating a small cyclodialysis next to the scleral spur. The stent’s proximal end remains in the anterior chamber next to the iris root. Promising results have been reported with this type of stent, but controlled studies are needed to confirm preliminary results. Trabecular micro-bypass stents and other gonioscopic surgery modalities may in fact offer interesting alternatives within surgical glaucoma treatment options in the near future. Few, nonsevere complications were described compared to filtration surgery. Furthermore, this surgery can be repeated and more than one stent is used. The conjunctiva is left untouched, leaving the option for more invasive surgeries in later stages. Device cost is currently high, but it will tend to fall. Obviously, the preliminary data described here will have to be confirmed in prospective studies involving more patients and longer follow-up. However, if first

impressions are confirmed and stent improvement continues, we believe that this far better developed concept of anatomical approach will prove to be an interesting surgical option for glaucoma.

REFERENCES

1. Gutiérrez Díaz E, Rodríguez M. Dispositivos de drenaje para glaucoma, Madrid: Ediciones Ergon, S.A.; 2002.

2. Minckler S, Francis BA, Hodapp EA, et al. Aqueous shunts in glaucoma: A Report by the American Academy of Ophthalmology. 2008;115;1089-97.

3. Bahler C, Zhou J, Smedley G, et al. Trabecular by-pass stents decrease IOP in cultured human anterior segments. Am J Ophthalmol. 2004;138:988-94.

4. Spiegel D, Neuhann T, Wetzel W, et al. Coexistent POAG and cataract: interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery. European J Ophthalmol. 2009.

5. Fea AM. Phacoemulsification versus phaco with micro by-pass stent implantation in POAG. Cataract Refract Surg. 2010;36(3):407-12.

Canaloplasty 37

INTRODUCTION

Canaloplasty is a surgical procedure used in open-angle glaucoma in adults. It is considered an ab externo, nonpenetrating canal surgery, independent of bleb formation. The purpose of this surgical technique is to reinforce and restore the standard canalicular drainage pathway. This is achieved by increasing aqueous humor flow from the anterior chamber to Schlemm’s canal, which is distended by creating a trabeculodescemetic window and an intrascleral space. To distend Schlemm’s canal, 360º catheter viscodilation and suture tensioning canal are performed. It is believed that the mechanism of action of suture tensioning is similar to the pilocarpine mechanism in increasing trabecular meshwork per-meability.

INDICATIONS

Generic indications for glaucoma surgery are: medically uncontrolled glaucomas, glaucoma or ocular hypertension intolerant to medical therapy and therapy noncompliance. Medically uncontrolled glaucoma is defined as presence of disease progression signs, as shown by perimetry or focal or general increase in the cup/disk ratio. This surgical technique can be performed in all cases with camerular angle at least a Shaffer grade 3. It is indicated for: primary open-angle glaucoma; pseudoexfoliative glaucoma; pigmentary glaucoma; cortisone glaucoma; glaucoma in pseudophakic or phakic eyes; other open-angle secondary glaucomas (Table 6.1).

RELATIVE CONTRAINDICATIONS

Canaloplasty is contraindicated in narrow-angle glaucoma or plateau iris. However, these are no longer contraindications in the absence of peripheral anterior synechiae and if associated with phacoemulsification. Since canaloplasty is more proinflammatory than deep sclerectomy, in inflammatory glaucomas without anterior synechiae, deep sclerectomy is safer (Table 6.1).

ABSOLUTE CONTRAINDICATIONS

Absolute contraindications for canaloplasty are: absolute glaucoma; angle recession; neovascular glaucoma; chronic closed-angle glaucoma; narrow-angle glaucoma or plateau iris; previous surgery compromising Schlemm’s canal (Table 6.1).

Table 6.1: Indications and contraindications

Indications • Primaryopen-angleglaucoma

• Secondaryopen-angleglaucoma

Relative contraindications • Narrow-angle glaucoma orplateauiris

• Glaucomasecondary to angleanomalies:ICE,congenitalandjuvenile

Absolute contraindications • Absoluteglaucoma

• Anglerecession


• Chronicclosed-angleglaucoma

(ICE:Iridocornealendothelialsyndrome)


Canaloplasty 6


PATIENT’S ASSESSMENT

In addition to general ophthalmological assessment, it is crucial to assess eye surgery history in patients who are candidates for canaloplasty. If there is a history of cataract surgery, we must find out whether it was performed by phacoemulsification or extracapsular extraction, whether an intraocular lens was inserted, and whether the surgery had complications. In patients with a history of trabeculoplasty, the location on trabeculum should be determined, plus whether there were any repetitions and which type of trabeculoplasty was performed: argon, diode or selective laser trabeculoplasty. Glaucoma characterization is the key. This requires careful anterior segment analysis, detailed gonioscopy description and, if possible, anterior segment optical coherence tomography (OCT) (Figs 6.1A and B), 80 MHz ultrasound (Fig. 6.2) or ultrasound biomicroscopy (UBM). As it is a nonpenetrating surgery, success requires that eyes with or which may favor peripheral anterior synechiae be excluded.

SURGICAL TECHNIQUE

Before describing the surgical technique itself, some of the new instruments used in canaloplasty will be presented. For Schlemm’s canal catheterization, a flexible microcatheter is used (Fig. 6.3) with an atraumatic tip diameter of 250 µm and a diameter of 200 µm along the catheter (iTrack, iScience Inter ventional, Menlo Park, California, USA). This microcatheter is composed of two compartments: one delivers viscoelastic material and is connected to an ejector; another compartment has an optical fiber connected to a diode laser-based microillumination system (Fig. 6.4) (iLumin, Menlo Park, California, USA). For angle study, and pre-, peri- and postoperative Schlemm’s canal positioning, iScience Interventional has marketed iUltrasound (Fig. 6.5). With an 80 MHz frequency, the ultrasound probe enables high resolution

anterior chamber scanning of approximately 4 mm × 3.5 mm. Acquisition is by contact. To enable intra- and immediate postoperative use, sterile disposable probe capsules and protective sleeves are available.

Preoperative Preparation

Preoperative preparation includes application of one drop of 2% pilocarpine 30 minutes before surgery. The author prefers initiating prophylaxis for endophthalmitis 3 days before surgery with broad-spectrum antibiotic eye drops, combined with topical nonsteroidal anti-inflammatory eye drops. Before the surgery itself, lateral paracentesis with a 15° blade should be performed. This can be used in several surgery stages. Paracentesis can also be done immediately before entering Schlemm’s canal. Magnification should be adapted to control each surgical step.

Surgery Location

The procedure is generally performed at 12 o’clock. Operative field exposure is essential for quick, uncomplicated surgery. When adequate exposure cannot be obtained, it is advised to pass a W-shaped suture at 10 and 2 o’clock using a 10/0 polyamide or 8/0 polyglactin 910 suture (Fig. 6.6). This technique allows you to turn the eye inferiorly, and to hold the scleral flap during part of the surgery, allowing the assistant surgeon to perform other tasks. Surgery should begin by opening the conjunctiva and Tenon’s capsule at the limbus for approximately 8–10 mm to expose the sclera. The superficial sclerotomy location should be free of collecting ducts, if possible. To keep the work area as dry as possible, vessel cauterization can be performed using thermal cautery or diathermy. Scleral dissection area should have a parabolic shape, with a base of approximately 5 mm and length of 5 mm. Scleral areas can be marked with a compass or a customized marker (Fig. 6.7).

Fig. 6.1A: Narrow-angle, contraindicated for canaloplastySource: SL-OCT (Heidelberg Engineering)

Fig. 6.1B: Open-angle, without contraindication for canaloplastySource: SL-OCT (Heidelberg Engineering)

Canaloplasty 39

Fig. 6.2: Relative contraindications for canaloplastySource: iUltrasound (iScience Interventional)

Fig. 6.3: Diagram of iTrack microcatheter

Fig. 6.4: iTrack microcatheter without light, connected to viscoelastic ejector, iLumin light source and illuminated iTrack microcatheter

Fig. 6.5: iUS probe with sterilized capsule

Fig. 6.6: Scleral flap secured with a W-shaped suture Fig. 6.7: Parabolic marker Kearney, Duckworth and Kent, UK


Scleral Flaps, Opening of Schlemm’s Canal Opening and Creation of a Trabeculodescemetic Window

After marking a parabolic scleral area, a scleral flap of approximately 1/3 of total scleral thickness is dissected. For scleral flap dissection, the surgeon suggests using a 1.25 mm, mini-crescent angled knife (Sharpoint, PA, USA). Superficial scleral flap dissection should extend up to approximately 1 mm into the clear cornea (Fig. 6.8A). A deeper flap can then be drawn over the previous flap’s bed, approximately 1 mm from its edge (Fig. 6.8B). The deeper flap is then dissected with 90° edges (Fig. 6.8C) and very close to the ciliary body/choroid, slowly extending to the anterior globe until it reaches Schlemm’s canal. If the eye is very tense, some aqueous humor should be removed by paracentesis immediately before reaching Schlemm’s canal [intraocular pressure (IOP) should remain within 5–10 mm Hg]. This will prevent perforation of the inner wall of Schlemm’s canal or Descemet’s membrane. Dissection should then open Schlemm’s canal and create a trabeculodescemetic

window. A window can be obtained by proceeding with deep scleral flap dissection as far as Descemet’s membrane in the clear cornea. The size of the descemetic window should be approximately 500 µm anterior to Schwalbe’s line (Figs 6.9A and B). After creating a trabeculodescemetic window, deep scleral flap excision should be performed with Galand scissors (Huco, Switzerland, 42350). After carefully dissecting the Schlemm’s canal ostium, the canal is dilated with 1.4% sodium hyaluronate (Healon GV, AMO, Abbott Park, II, USA) using a Grieshaber cannula (Fig. 6.10). This surgical stage should be performed under strong magnification to control each step. According to training instructions for this techni-que, peeling the inner wall of Schlemm’s canal should be performed if percolation of aqueous humor through the trabecular meshwork and trabeculo-descemetic window is insufficient. To assess the amount of aqueous humor percolation, clean the field thoroughly with a triangular rod, followed by a dry rod, and then quantify the time it takes to become wet. Ideally, this should be 15 seconds. The inner wall of Schlemm’s canal can be peeled under

Fig. 6.8A: Dissection of a superficial scleral flap Fig. 6.8B: Delimitation and dissection of a deep scleral flap

Fig. 6.8C: Diagram of dissection edges, creation of perpendicular edges

Canaloplasty 41

Fig. 6.9A: Trabeculodescemetic window Fig. 6.9B: Trabeculodescemetic window and intrascleral space obtained intraoperatively by iUltrasound (iScience Interventional)

Fig. 6.10: Schlemm’s canal dilation

large magnification using a Mermoud forceps (Ref. 3.4475, Huco, Switzerland).

Catheterization, Dilation and Distention of Schlemm’s Canal

Before catheterizing Schlemm’s canal, the surgeon must fill in the injector with viscoelastic material, test viscoelastic flow along the microcatheter and connect to the light source. After testing viscoelastic flow along the iTrack microcatheter, we must wait for the viscoelastic outflow to be residual and fasten the catheter to the operative field so that no pressure is exerted when it is pushed into the canal. Then, low eye tonicity should be confirmed and catheterization started through the ostium on the left-hand side if the surgeon is right-handed (Fig. 6.11A). Magnification should be

appropriate for full microcatheter path visualization and microscope and room lighting should be reduced for microillumination to be properly visible. After the microcatheter has exited through the opposite ostium in the Schlemm’s canal, the double 10/0 polypropylene suture is tied with a double knot (Prolene, Ethicon Inc, Switzerland) (Fig. 6.11B). Then, the surgeon should confirm that the suture is free and go the opposite way to remove the microcatheter and place the suture thread in the canal. This movement should be performed smoothly at a constant speed. If we see the ocular globe as a clock face, viscoelastic material should be injected every 2 hours (one click on the injector: 0.5 µl). After the microcatheter has exited the canal, the microcatheter thread is cut and the two threads are separated. Holding both ends of the same thread, Schlemm’s canal is anteriorly distended and the first two knots are tied. Suture thread tension is checked by pulling the thread towards the scleral spur; the knot should not go beyond the scleral spur (Figs 6.12A and B). The anterior chamber is filled in and Schlemm’s canal distention is checked using the iUS system (Fig. 6.12C). After achieving optimal distention, the second knot and a braking knot are tied. The same is done for the second thread.

Closure of Scleral Flap and Conjunctiva

Finally, the scleral bed is filled with viscoelastic material and the superficial scleral flap is sutured. The suture should be waterproof. It should be remembered that the purpose of this surgery is not to be a filtration surgery for subconjunctival space, but to create a


Fig. 6.11A: Catheterization of Schlemm’s canal Fig. 6.11B: Double 10/0 polypropylene knot

Fig. 6.12A: Tension assessmentFig. 6.12B: Correct tension scheme

Fig. 6.12C: Image of dilated Schlemm’s canal with viscoelastic material and properly distended suture threadSource: Intraoperatively by iUltrasound

scleral lake for aqueous humor to be drained through the trabeculodescemetic window, with access to the distended Schlemm’s canal and collecting ducts, and to reconstruct physiological drainage pathway. A 10/0 nonabsorbable (polyamide) or absorbable (poly glactin 910) suture should be used to close the flap. In general, five suture stitches are used: two next to the limbus, one at the distal parabolic end and the other two at intermediate positions (Figs 6.13A and B). After five suture stitches, wound waterproofness is checked by introducing BSS into the anterior chamber and checking whether it leaks through the surgical wound. If leaks occur, another suture should be placed at the Seidel site. The conjunctiva should be tightly closed with two simple stitches using an 8/0 polyglactin 910 suture. At the end of the surgery, the chamber should be

Canaloplasty 43

well formed and estimated IOP should be approximately 20 mm Hg. At the end of the surgery, an ultrasound scan can be performed for distention control, canal dilation, visualization of iridocorneal angle (very important to check that no postoperative peripheral anterior synechiae are present), intrascleral bed extension and trabeculo-descemetic membrane (Figs 6.14A and B). For endophthalmitis prophylaxis, the author uses a subconjunctival cefazolin injection, followed by broad-spectrum antibiotic eye drop instillation five times a day for 15 days. As an anti-inflammatory and antifibrotic treatment, the author usually uses a subconjunctival betamethasone injection perioperatively, followed by prednisolone and flur biprofen instillation five

Fig. 6.13A: Correct scleral flap closure suturing Fig. 6.13B: 36-h image of surgical wound

Fig. 6.14B: Dilated, distended Schlemm’s canalSource: Intraoperative iUltrasound once surgery is complete

Fig. 6.14A: Intrascleral space and trabeculodescemetic window Source: Intraoperative iUltrasound once surgery is complete

times a day for 1 month after surgery. For prophylaxis of peripheral anterior synechiae, the surgeon usually instils one drop of 2% pilocarpine at the end of the surgery. In combined surgery involving canaloplasty and phacoemulsification with intraocular lens insertion, the procedure should start with canaloplasty until accessing the Schlemm’s canal. No trabeculodescemetic window should be created (scleral flap dissection is facilitated by higher eye tonicity, but opening the canal and creating a descemetic window before phacoemulsification may lead to its rupture). Cataract surgery is performed and afterwards the canaloplasty is resumed. Some surgeons prefer to perform cataract surgery first and afterwards the canaloplasty.


Difficulties/Complications and their Intraoperative Resolution

Depth of Deep Scleral Flap

As in all surgical techniques, difficulties and compli-cations occur less often as the learning curve develops. One of the initial difficulties is to determine the ideal depth for the deep scleral flap. When a parabola flap is delineated with the 15° blade, we must be able to see through the remaining sclera to the choroid, and dissect a little with the blade before changing to the mini-crescent blade. The same plane should always be kept and if the flap’s lateral edges have to be freed, the blade should be vertically positioned to follow upward movements. When the transition line between the sclera and the trabecular meshwork is reached and the plane is superficial to Schlemm’s canal, a new deeper flap should be performed. A deeper flap should then be made at the flap’s distal portion (avoiding a deeper cut right next to the trabecular meshwork). The deep scleral flap should only be cut after finding and opening Schlemm’s canal and creating a descemetic window. But if the deep scleral flap is too deep and exposes the choroid/ciliary body (choroidal/ciliary body hernia), a more superficial scleral plane should be found away from that area to avoid making the hernia bigger. In a protuberant hernia, the IOP should be decreased by paracentesis. Once a new plane has been found the surgery can proceed.

Perforation of Trabeculodescemetic Window

Opening Schlemm’s canal, creating a trabeculo-descemetic membrane, peeling of the inner wall of Schlemm’s canal and cutting a deep scleral flap are the most sensitive moments of the surgical technique. Perforation may occur at any of these stages. If it does, the action will depend on perforation size, presence of prolapse of the iris or loss of the anterior chamber. In a microperforation, acetylcholine chloride (Miochol®) should be injected in the anterior chamber and the procedure to be continued. In a macroperforation with loss of anterior chamber but no prolapse of the iris, administer a miotic drug, air bubble or viscoelastic material in the anterior chamber, perform peripheral iridectomy (to avoid postoperative iris incarceration) and then proceed with the surgery. In a macroperforation with prolapse of the iris, peripheral iridectomy should be performed, administering a miotic drug, air bubble or viscoelastic material in the anterior chamber. The surgery can then proceed if the surgeons are sure that the wound is tightly closed. In a nonlinear perforation with anterior chamber shape loss, even after air bubble or viscoelastic insertion, the surgery must be finished by ab externo trabeculectomy (Flow chart 6.1).

Canal Catheterization

1. Microcatheter passage into the anterior chamber or suprachoroid space: Remove the microcatheter,

Flow chart 6.1: Perforation of trabeculodescemetic window

Canaloplasty 45

check whether the Schlemm’s canal ostium is clear and inject BSS into its entry port, checking whether collecting vessels become transparent. When this happens, the procedure can be resumed. If a false pathway persists, catheterization should be initiated in the opposite ostium.

2. Entry in collecting canal: Move the catheter back, approximately 2h (sometimes collecting canals run parallel to Schlemm’s canal), exert external pressure with the forceps to try to collapse the collector canal and proceed with catheterization. Sometimes, IOP is very low at this stage, which may facilitate entry in collecting canals. In that case, restore the anterior chamber with BSS (remember to lower IOP when working with suture to distend the canal). If you still cannot pass the collecting canal, you may try a small microcatheter angulation or initiate catheterization through the opposite ostium.

3. When distending Schlemm’s canal or tying a knot, the suture may break: If only one thread breaks, the procedure can be finished with one thread only. If both threads break, Schlemm’s canal needs to be recatheterized with a new suture (without viscoelastic material insertion).

4. Descemet’s membrane detachment: In this case, injecting viscoelastic material into Schlemm’s canal is not advisable. A small detachment does not require special care other than targeting an IOP of about 20 mm Hg at the end of surgery. A large detachment with visual axis involvement or immediate bleeding requires the blood to be flushed out and the anterior chamber filled with viscoelastic material and/or air bubble at the end of the surgery.

Hyphema

Reflux hyphema may sometimes arise during surgery. This should be cleaned and surgery should end with an IOP of approximately 20 mm Hg to avoid presence of hyphema at the end of the surgery.

Immediate Postoperative Complications and Resolution of Complications (1–10 Days)

Hematic Tyndall/Hyphema

This is perhaps the most common complication, almost always arising from episcleral reflux for hypotony. This is a “physiological” reaction. There are reports that these are more common in patients who have undergone prior trabeculoplasty. In general, it is small and resolves

spontaneously after a few days. As before, this may be minimized targeting an IOP of 20 mm Hg at the end of the surgery.

Ocular Hypertension

High intraocular pressure: Rule out iris incar ceration in the trabeculodescemetic window; formation of peripheral anterior synechiae; presence of viscoelastic material in a combined procedure; hyphema; response to corticoids. If peripheral anterior synechiae are present in the trabeculodescemetic window secondary to micro- or macroperforation with iris incarceration: try to release the iris with pilocarpine or Nd:YAG laser synechiolysis, but if it does not respond surgical review with peripheral iridectomy must be performed.

Hypotony

If transient, one should wait.

Descemet’s Membrane Detachment

Descemet’s membrane detachment is more common in eyes that have previously undergone trabeculoplasty, when much viscoelastic material was injected during catheterization or when catheterization is stopped. A small detachment which does not involve visual axis will resolve in approximately 2–4 months with no further consequences (Figs 6.15A and B). If Descemet’s membrane detachment is filled with blood, this should be removed by partial paracentesis. If it involves visual axis with or without hematic collection, in addition of removing blood, the anterior chamber should be filled with an air bubble or viscoelastic material.

Low Anterior Chamber

Search for Seidel or iris incarceration within the wound.


This is rare in any nonpenetrating procedure. If small, there is no specific therapy; if large, consider cycloplegia with atropine and anti-inflammatory therapy reinforcement.

Reduced Visual Acuity

There may be temporary vision loss which will recover in approximately 1–3 months. One cause may be induced astigmatism [this may be avoided if superficial scleral flap suture is performed after filling the anterior chamber and with an absorbable suture (polyglactin 910)].


Late Postoperative Complications and Resolution of Complications (2–5 Weeks)

Increased Intraocular Pressure

This may be associated with:• Sclerallakecollapse:considergoniopuncture• Formationofperipheralanteriorsynechiaeatthe

trabeculodescemetic window secondary to micro- or macroperforation with iris incarceration. If recent, the iris could be released with 2% pilocarpine or Nd:YAG laser synechiolysis, but if it does not respond surgical review with peripheral iridectomy must be performed (Fig. 6.16).

Suture Exposure in the Anterior Chamber

Generally secondary to trauma or intense Valsalva maneuver, the eye remains under observation.

REMARKS

Canaloplasty is a safe and effective procedure for adult open-angle glaucoma treatment. Despite having a longer learning curve and surgical time than other surgical techniques, canaloplasty involves a very small number of intra- and postoperative complications. By trying to restore the physiological aqueous humor drainage pathway, the procedure not only benefits from the advantages of a nonpenetrating method, but is also independent of bleb formation, and therefore independent of one of the main failure mechanisms of filtration surgery. Canaloplasty does not require antimetabolites, needling or postoperative massage. Hyphema is the most frequent complication. This is a minor complication and results from episcleral venous reflux, indicative of distal drainage pathway patency to Schlemm’s canal and trabecular meshwork permeability to blood cells. The main cause of concern is suture intrusion in the anterior chamber, but published work does not consider this to have any clinical implications. Although canaloplasty is already performed in multiple surgical centers, with over 15,000 procedures, it is expensive. In addition to supporting equipment, the microcatheter is intended for single use. Few studies

A

Fig. 6.16: Iridotrabeculodescemetic synechiae

Figs 6.15A and B: Small Descemet’s membrane detachment which is resolved with no consequences after 4 months

B

Canaloplasty 47

have been published that show the actual economic impact/sustainability of canaloplasty at 5 or more years. From the published work, the author chose those she regards as the most significant, three of them with 12-month results and one with 3-year results. Three of the articles consider canaloplasty as a single procedure and one as a combined procedure with phacoemulsification. Lewis et al.1 describe 12-month results for 94 patients who underwent canaloplasty in a multicenter study. Intracanalicular suture was placed in 74 patients (79%). The mean baseline IOP was 24.7 ± 4.8 mm Hg with a mean of 1.9 ± 1.0 medications per patient. In patients whose surgery was successful, the mean IOP at 12 months was 15.3 ± 3.8 mm Hg, with a mean of 0.6 medications per patient. The IOP decreased 38%. To study the suture tensioning effect on IOP reduction, they performed a camerular angle ultrasound study at 1 year. The authors have noted that patients with minimal Schlemm’s canal tension showed lower tension decrease than patients with higher Schlemm’s canal tension (24% versus 40%). They have concluded that canal distention has implications for IOP reduction. Complications were reported in 16% of the patients: three cases of hyphema, three with IOP > 30 mm Hg and four patients were subsequently converted to trabeculectomy. Grieshaber et al.2 describe 12-month results for 33 patients undergoing canaloplasty only. The mean perioperative IOP was 27.3 ± 5.6 mm Hg with a mean of 2.7 ± 0.5 medications per patient. In patients with completed surgery, the mean IOP at 12 months was 12.8 ± 1.5 mm Hg, with a mean of 0.1 ± 0.3 medications per patient. The complete 12-month success rate of an IOP ≤ 18 mm Hg was 84.4% and goniopuncture was performed in 18.1% of the eyes. This publication reported the following complications: inability to complete canaloplasty in one eye, two Descemet’s membrane detachments, elevated postoperative IOP in one eye, and suprachoroidal/anterior chamber passage of the catheter in four eyes.

Shingleton et al.3 describe 12-month results for 54 patients submitted to simultaneous canaloplasty and phacoemulsification in one multicenter study. The mean baseline IOP was 24.4 ± 6.1 mm Hg with a mean of 1.5 ± 1.0 medications per eye. In patients with completed surgery, the mean postoperative IOP at 12 months was 13.7 ± 4.4 mm Hg, with a mean of 0.2 ± 0.4 medications per patient. The IOP decreased 44%. Complications were reported in 9.3% of the patients: hyphema in three eyes, Descemet tear and iris prolapse in one eye. The study with the highest decrease (3 years) was conducted on a black African population,4 in which failure rate with bleb-dependent techniques, even using antimetabolites, is high. The mean preoperative IOP was 45.0 ± 12.1 mm Hg. In patients who underwent complete successful surgery, the mean IOP at 36 months was 13.3 ± 1.7 mm Hg. The complete 36-month success rate (IOP ≤ 21 mm Hg) was 77.5% and qualified success rate was 81.6%. Of 60 eyes undergoing surgery, two Descemet’s detachment, one elevated IOP and two false passages of the catheter were found. Microhyphema (< 2 mm) was the most common finding in the immediate postoperative period (42 eyes) with resolution in less than 7 days. There were no vision changes after 3 years.

REFERENCES

1. Lewis RA, Wolff K, Tetz M, et al. Canaloplasty: circumferential viscodilation and tensioning of Schlemm’s canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults. Interim clinical study analysis. J Cataract Refract Surg. 2007;33:1217-26.

2. Grieshaber MC, Fraenkl S, Schoetzau A, et al. Circum-ferential viscocanalostomy and suture canal distention (canaloplasty) for whites with open-angle glaucoma. J Glaucoma. 2011;20:298-302.

3. Shingleton B, Tetz M, Korber N. Circumferential viscodilation and tensioning of Schlemm canal (canaloplasty) with temporal corneal phacoemulsification cataract surgery for open-angle glaucoma and visually significant cataract. J Cataract Refract Surg. 2008;34:433-40.

4. Grieshaber MC, Pienaar A, Olivier J, et al. Canaloplasty or primary open-angle glaucoma: long-term outcome. Br J Ophthalmol. 2010;94:1478-82.


INTRODUCTION

“When glaucoma surgery is indicated and there is a visually significant cataract, the two procedures can be performed combined or sequentially. The decision is to be made according to the clinical findings, after discussing with the patients advantages and disadvantages of each approach.”1

The above paragraph summarizes, simply and broadly, the correct attitude to simultaneous glaucoma and cataracts. As we know, this is a very common comorbidity. However, in real, daily clinical practice the decision is not as simple as it appears. This chapter discusses the multiple factors to be considered in therapeutic decisionmaking, and draws attention to relevant patient examination aspects. The technique is then described with a reference to the nature of the intra and postoperative complications which may arise.


Choosing between sequential versus combined surgery is more complex that we may, at first, think. The choice is based not only on factors associated with the patient’s clinical status, but also on surgeonrelated factors and, also important, on organizational and/or economic issues. Marked advances and highquality results with phacoemulsification, including clear corneal incisions (which are currently 1.8–2.2 mm in length), plus the development of new materials and devices to solve such common problems as miosis, zonular instability, and

lowdepth anterior chambers, have allowed the almost imperceptible combination of phacoemulsification with glaucoma surgery. As mentioned in the Consensus Series2, a combined procedure is indicated when surgery to lower intraocular pressure (IOP) is appropriate and a visually significant cataract is also present.2

Our discussion will focus on openangle glaucoma (OAG), because, as we know, primary and secondary angleclosure glaucomas have very different reasons for requiring cataract surgery, which may be related to resolving existing glaucoma. Although this chapter is intended to describe a practical approach to combined surgery, and it is not meant to summarize relevant publications on the subject or to provide an exhaustive list of literature references, we will nonetheless mention some study results for their importance in therapeutic decisionmaking.3

Some publications report lowering IOP in OAG patients with cataract surgery alone.4,5 However, this reduction is unpredictable, transient and not significant at approximately 2 mm Hg one year after surgery.6

But other papers show a higher risk of IOP increase in the immediate postoperative period, when phacoemulsification alone is performed.7 This, as well as evidence of loss of glaucoma surgery efficacy when cataract surgery is performed afterwards,8 and knowledge of probable progression of existing lens opacities after glaucoma surgery,9,10 are important arguments in favor of combined surgery.

Teresa Gomes

Combined Surgery 7

Combined Surgery 49

However, the lower hypotensive effect of combined surgery compared with trabeculectomy, as reported in several papers,11 may lead us to see sequential surgery as a better option in patients whose glaucoma requires fast and effective IOP lowering. But, this evidence of a lower hypotensive effect of combined surgery is not consensual across the literature, and many studies report similar efficacy for sequential and combined surgery, in terms of both IOP and final visual acuity.2,12

After these theoretical considerations, our option in case of comorbidity is for combined surgery, if possible. This option takes into account the increasing organizational constraints in current practice. Still, good results have been obtained for years and they are definitely the most important factor in our choice. In the past four decades, the most common combined surgical technique has been phacotrabeculectomy (phacotrab), which most publications report on, but new techniques have emerged over the years as valid alternatives to classic surgery, including: nonpenetrating deep sclerectomy (NPDS), viscocanalostomy, canaloplasty, the use of ExPress®, Trabectome®, or iStent. Some of these techniques are described elsewhere in this book. In this chapter on combined surgery, we will only discuss trabeculectomy and NPDS. As stated in the Consensus on glaucoma surgery, it is not possible to define strict criteria or precise indications for combined surgery. It is not possible to define an IOP level and/or visual acuity level at which combined surgery should always be performed. Such simple criteria do not exist, and decisionmaking should be tailored to each case and discussed with the patient. Despite the need to adapt the surgical technique to each patient, there are some general guidelines for combined surgery:• NeedforIOPloweringinapatientpresentingwith

cataracts causing significant loss in visual acuity.• RiskthatanIOPriseafterphacoemulsificationmay

cause significant loss of visual function.• Needtocarryoutgeneralanesthesia.• Need for IOP lowering in a patient presenting

with progressing cataracts, although not yet with significant loss in visual acuity.

• Intolerancetotopicaldrugsinapatientpresentingwith cataracts causing significant loss in visual acuity.

• Poor compliance in a patient presenting withcataracts causing significant loss in visual acuity.

Contraindications for combined surgery may be:• Need for fast, significant IOP loweringwith the

highest probability of success and the lowest complication rate.

• Surgeonlackingexperienceinmodernphacoemulsification techniques (clear cornea, small incision).

We believe that although combined procedures have potential disadvantages (more complex surgery, greater probability of perioperative complications such as hypotony, shallow anterior chamber, hyphema, persistent uveitis), they also offer clear benefits: they prevent an IOP rise after phacoemulsification, enable an immediate visual acuity improvement and limit patient exposure to two surgeries on separate occasions and their potential complications.

PATIENT’S CLINICAL EVALUATION

Before proceeding to surgical intervention, the surgeon must perform a full, detailed patient assessment. The evaluation should begin by obtaining the patient’s relevant personal history (PH). It is crucial to know: ongoing systemic therapy [platelet antiaggregation (PAA), oral anticoagulants (OAC), alphaagonists], if necessary, an internist or a cardiologist to consider discontinuation; presence of systemic disease that may influence the type of anesthesia, i.e. hypoacusis, Parkinson’s and dementia; current topical therapy, consider continuing, interrupting or replacing. At this stage, it is very important to talk to patients to properly address their expectations and fears. The patient should be aware of the risks and benefits of the combined surgery. Patients should play an active role in designing the therapeutic strategies they are going to experience. A knowledgeable patient is usually a more understanding, cooperative patient. After obtaining the patient’s history, objective examination will follow. Diffuse light and slitlamp examination are essential and may completely change the intra and postoperative course. Lacrimal duct obstruction, dacryocystitis, conjunctivitis, blepharitis, ectropion, entropion, and trichiasis should be diagnosed and treated before surgery. In the anterior segment, risk factors for cataract and/or glaucoma surgery should be identified, such as endothelial dystrophy, phacodonesis, presence of pseudoexfoliative material and iris neovascularization. Different variants of capsular tension rings should be available, as well as an adequate ophthalmic


viscosurgical device (OVD) for each situation. In some patients, using an anti vascularendothelial growth factor (VEGF) before the combined surgery should be considered. Gonioscopy should always be performed; the presence of synechiae or closed angle areas may influence the choice of glaucoma surgery procedure. The presence of iris neovascularization or anterior synechiae is decisive in choosing the intraocular lens (IOL) for the anterior chamber (AC) in the event of a complicated surgery. Anglesupport IOLs should be avoided in such cases to prevent postoperative uveitisglaucomahyphema (UGH) syndrome. It is also extremely important to assess mydriasis to predict the need to use retractors or any other intraoperative device to reverse miosis. In patients with marked conjunctival hyperemia resulting from current topical therapy, its replacement with another topical or per os drug until the surgery day should be considered. We usually do not use antibiotics, nonsteroidal antiinflammatory drugs (NSAIDs) or topical steroids before surgery.

SURGICAL TECHNIQUE AND COMPLICATIONS

The technical details below have not been chosen in the wake of efficacy study results, because no such studies exist. In fact, as stated in the Consensus, there is no evidence that can provide an answer to the following questions:• Whattypeofanesthesiaismoreappropriate?• One-site versus two-site approach, which one isbetter?

• Limbal versus fornix-based conjunctival incision,whichoneisbetter?

• Should intraoperative antimetabolitesbeused inallcombinedsurgeries?

• Whattypeof scleral flapclosure shouldbeused(releasable,suturelysis?)

• WhatistheidealIOL?• ShouldtheOVDbeleftintheACattheendofthesurgery?

The choices mainly depend on each surgeon’s learning over the years, efficacy results and presence of complications. The choice of the type of anesthesia depends mainly on the surgeon’s experience and preference. We prefer using topical anesthesia with oxybuprocaine associated with subconjunctival infiltration with 1%, preservativefree lidocaine, which in case of trabeculectomy is also used in the anterior chamber at the time of iridectomy.

Use of general anesthesia almost always results from poor patient compliance (hypoacusis, Parkinson’s, dementia, and others). For us, peribulbar and retrobulbar anesthesia are never an option in combined surgery. Our experience in combined surgery is phacotrab and phaco + NPDS. As Weitzman and Caprioli,13 the surgeons always prefer making two separate incisions, one for the phaco and another for the glaucoma surgery. Phaco is always the initial procedure, using a temporal, clearcornea approach (Fig. 7.1). The incision may range from 2.2 mm to 2.85 mm depending on material availability or according to the surgeon’s criterion. At the end of cataract surgery and before beginning glaucoma surgery, MIOCHOL® is injected and the OVD device is left in the anterior chamber for trab and removed for NPDS. Finally, the main incision is irrigated with balanced salt solution (BSS) until it is watertight. Although we do not induce lid or ocular globe akinesia, we rarely use traction sutures. When we do use them, silk or dexon 6/0 or 7/0 sutures are applied using a spatulated needle, placed at 6 o’clock or 3 and 9 o’clock at the limbus. When possible, filtration surgery flaps are made at 12 o’clock leaving the temporal and nasal quadrants available for future interventions. The choice depends on conjunctival mobility and scleral integrity. A peritomy approximately 6 mm in length is performed without leaving residual conjunctiva, and Tenon’s capsule is only removed when it is excessively thick, such as in young patients, reinterventions, and black patients. When it is planned to use mitomycin C (MMC), either the excision is not made or it is as

Fig. 7.1: Phaco, temporal approach

Combined Surgery 51

limited as possible. SubTenon’s dissection should be increased towards the fornix in order to guide drainage in that direction. Scleral vessel diathermy should be very mild, essentially in NPDS. A quadrangular 5 × 5 mm, limbusbased scleral flap should be created. In trabeculectomy, the thickness is approximately 1/2 to 1/3 of the total thickness, whereas in NPDS another flap is cut, up to 90–95% of the total thickness, maintaining the same superficial format and having sides of 3.5–4 mm. When an antimetabolite is used, the edges perpendicular to the limbus should not go beyond it; in the NPDS, it should extend approximately 1 mm further. We shall now look at the use of antimetabolites in combined surgery. Some authors argue that they should be used systematically. Published studies show a slight increase in combined surgery efficacy when antimetabolites are used,14,15 but their use is associated with an increase in perioperative complications.16 We have been choosing not to use antimetabolites in NPDSs and to use them in trabeculectomy only in the presence of associated failure risk factors, such as: prior surgery (essentially with conjunctival incision), ongoing inflammatory process, neovascular glaucoma (we use intravitreous antiVEGF in the week prior to surgery), black patients, longterm, proinflammatory antiglaucoma therapy. As in all the aspects we have discussed for surgical techniques, this procedure is also open to question. Ever since we started using nonpenetrating surgery techniques in 2000, we have chosen not to use antimetabolites. This may be due to Stegmann’s influence, who was then upholding the virtues of a truly minimally invasive procedure (he preferred viscocanalostomy), which was not compatible with the administration of such strong substances as MMC or 5FU. Our experience only involves using MMC, which we administer as a 0.2 mg/mL concentration on a cellulose sponge placed under the conjunctiva and under the scleral flap for 1–3 minutes. The higher the number of risk factors, the longer the exposure time. The MMC application area is then rinsed with at least 20 cc saline, and the forceps and the blepharostat are both replaced, as well as the surgical field, and the surgeon’s and assistant surgeon’s gloves. Trabeculectomy is then performed using a Kelly punch, with just one cut. The rest of the procedure is the same as when MMC is not used.

When NPDS is performed for glaucoma surgery, we always use implants in the scleral lake. Our experience includes using SKgel®, Aquaflow®, Tflux® and, more recently, Esnoper®. The technique is exactly the same as that used in glaucoma surgery alone. The surgical technique is as follows: 1. Peritomy, of approximately 6 mm (Fig. 7.2A). 2. Limbusbased, 5 × 5 mm square scleral flap, of

approximately 1/3 of total scleral thickness; flap edge should overlap the limbus by approximately 1 mm towards the cornea (Fig. 7.2B).

3. Square 4 × 4 mm deep flap, leaving 5–10% of total scleral thickness (Fig. 7.2C).

4. Peeling of the inner wall of Schlemm’s canal and juxtacanalicular trabeculum (Fig. 7.2D).

5. In the case of the Esnoper® implant, a suprachoroidal pocket is made using a minicrescent blade, in the side parallel to the limbus, towards the fornix.

6. Both Aquaflow® and Esnoper® are attached to the scleral lake with one 10/0 nylon suture stitch (Fig. 7.2E), the Esnoper® upper limit should not extend beyond the posterior limit of the trabeculodescemetic window.

7. The superficial scleral flap is sutured with two monofilament suture stitches at the angles (Fig. 7.2F).

8. The conjunctival flap is anchored to the cornea with two 10/0 nylon suture stitches (Fig. 7.2G).

We do not perform subconjunctival therapy, we only repeat conjunctival fornix rinsing with diluted iodopovidone. At the end of glaucoma surgery, we recheck the phaco incision closure and confirm that the anterior chamber has a good amplitude. If necessary, more OVD is injected in the anterior chamber. Postoperatively, antibiotic, nonsteroidal antiinflammatory and steroidal antiinflammatory therapies are maintained for 2–3 months. Combined surgery also combines the two separate surgeries’ complications. It would be excessive to state all the intra and postoperative problems of this procedure and their resolution. Although some authors have reported higher complication incidence in combined surgery, we do not find higher event rates in our patients. Their resolution is the same as when the operations are performed separately. In line with the literature, we have observed a lower incidence of perioperative complications when performing nonpenetrating surgery.


Fig. 7.2A: Peritomy Fig. 7.2B: Limbus-based scleral flap

Fig. 7.2C: Deep scleral flap Fig. 7.2D: Peeling of Schlemm’s canal

Fig. 7.2E: Implant in the scleral lake Fig. 7.2F: Superficial scleral flap suture

Combined Surgery 53

Fig. 7.2G: Conjunctival suture

Table 7.2: Postoperative complications

Postoperative Complications Resolution

Synechiae from iris to TD window◊ Topical miotic, potential YAG and/or argon laser

Hyphema•◊ Rest, mydriatic drug, possible AC rinsing

Choroid detachment•◊ Rest, mydriatic drug, increase in fluid consumption, avoiding Valsalva maneuvers

Filtration bleb leakage•◊ Occlusion, discontinuation of topical corticoids, inhibitor of carbonic anhydrase per os, large diameter CL, Palmberg sutures

Hyperfiltration•◊ Occlusion, discontinuation of β-blockers in the contralateral eye, potential revision to reinforce scleral flap suture

Athalamia with hypotony•◊ Treat the cause, topical mydriatic drugs, potential OVD in AC

Ocular hypertension•◊ Treat the cause (OVD in AC? sensitivity to corticoids?), massage, topical IOP lowering medications, increase corticoids (in a highly vascularized bleb), reduce corticoids (if few inflammatory signs), YAG in the TD window ◊, scleral flap suture lysis (only after the first week)

Cystic bleb•◊ Topical IOP lowering medications, bleb needling (with 0.02 mg/mL mitomycin)

Uveitis•◊ Reinforce topical corticoids, potential oral therapy, topical mydriatic drugs

Bleb dysesthesia•◊ Lubricants

Endophthalmitis•◊ ESCRS Guidelines, August 2007

(TD: Trabeculo-Descemet; YAG: Yttrium-aluminum garnet; AC: Anterior chamber; OVD: Ophthalmic viscosurgical device; IOP: Intraocular pressure; ESCRS: European Society of Cataract and Refractive Surgeons)◊ Nonpenetrating surgery• Trabeculectomy

Tables 7.1 and 7.2 list the perioperative compli cations, which we have faced more often, plus a brief note on their resolution; we do not mention cataract surgery complications. As you can see, some refer to nonpenetrating surgery, others are specific to trabeculectomy and others are common to both procedures.17

FINAL REMARKS

The search for the right attitude in patients with glaucoma and cataracts is still a challenge to the ophthalmologist. Choosing combined surgery is not

supported by strict criteria or protocols. This decision should be appropriate to each patient and depending on the results from the interaction of several factors. Evolution of cataract surgery technique and development of new glaucoma surgery techniques, some of which are performed ab interno through the same clear corneal incision as phacoemulsification, are completely changing the paradigm of combined procedures. Existing evidence does not support the validity of phacoemulsification alone as OAG therapy. Therefore, in cases requiring a more pronounced and longer lasting IOP reduction a surgical procedure, which improves filtration, must be added. From this perspective, combined surgery is an option with several advantages: only one surgical

Table 7.1: Intraoperative complications

Intraoperative Complications Resolution

Small TD window rupture◊ No change during the surgery

Large TD window rupture◊ Conversion to trab

Insufficient TD window drainage◊

Microperforation

Hyphema• Rinsing with BSS, filling AC with OVD

Athalamia• OVD in AC

(TD: Trabeculo-Descemet; OVD: Ophthalmic viscosurgical device; AC: Anterior chamber)◊ Nonpenetrating surgery• Trabeculectomy


stage, faster visual function improvement, avoidance of postoperative IOP rise after phacoemulsification, to name but a few. The constant use of an antimitotic in this surgery has been effective in improving results, but it increases medium and longterm complications. Some groups only use these substances when justifying risk factors are present. Finally, we must also highlight the importance of involving the patient in therapeutic decisionmaking; a knowledgeable, cooperative patient understands more about the potential complications and values more the success of preset strategies.

REFERENCES

1. European Glaucoma Society, Treatment principles and options, 3.7 Cataract and Glaucoma Surgery. Terminology and Guidelines for Glaucoma, 3rd edition; 2008. p. 157.

2. WeinrebRN,CrowstonJG.Glaucomasurgeryopenangleglaucoma. Consensus Series. Association of International Glaucoma Societies, Vol. 2. The Hague, The Netherlands: Kugler Publications; 2005. pp. 6572.

3. ShaarawyT,SherwoodM,HitchingsR,etal.“Glaucoma,Vol. 2. Surgical Management”; 2009.

4. ShingletonBJ,PasternackJJ,HungJW,etal.Threeandfive year changes in intraocular pressures after clear corneal phacoemulsification in open angle glaucoma patients, glaucoma suspects, and normal patients. J Glaucoma.2006;15:4948.

5. KimDD, DoyleWJ, Smith FM. Intraocular pressurereduction phacoemulsification cataract extraction with posterior chamber lens implantation in glaucoma patients. Ophthalmic Surg Lasers. 1999;30:3740.

6. PoleyBJ,LindstromRL,SamuelsonTW.Long-termeffectsof phacoemulsification with intraocular lens implantation innormotensiveandocularhypertensiveeyes.JCataractRefractSurg.2008;34:735-42.

7. LevkovitchVerbin H, HabotWilner Z, Burla N, et al. Intraocular pressure elevation within the first 24 h after cataract surgery in patients with glaucoma or exfoliation syndrome. Ophthalmology. 2008;115:1048.

8. DerbolavA,VassC,MenapaceR,etal.Long-termeffectof phacoemulsification on intraocular pressure after trabeculectomy.JCataractRefractSurg.2002;28:425-30.

9. ClarkeMP,VernonSA,SheldrickJH.Thedevelopmentof cataract following trabeculectomy. Eye. 1990;4: 57783.

10. The AGIS Investigators: The advanced glaucoma inter vention study, 8: risk of cataract formation after trabeculectomy. Arch Ophthalmol. 2001;119:17719.

11. Hurvitz LM. Combined surgery for cataract and glaucoma. Curr Opin Ophthalmol. 1993;4:738.

12. VassC,MenapaceR.Surgicalstrategiesinpatientswithcombined cataract and glaucoma. Curr Opin Ophthalmol. 2004;15:616.

13. WeitzmanHJ,Caprioli.Temporal cornealphacoemulsi-ficationcombinedwithsuperiortrabeculectomy.JTransOphthalmology Society. 1996;22:352.

14. Shin DH, et al. Longterm filtration and visual field outcomes after primary glaucoma triple procedure with and without mitomycinC. Ophthalmology. 2002;109:160711.

15. JampelHD,FriedmanDS, Lubomski LH, et al. Effectof technique on intraocular pressure after combined cataract and glaucoma surgery: an evidencebased review. Ophthalmology. 2002;109:221524.

16. Debry PW, Perkins TW, Heatley G, et al. Incidence of lateonset blebrelated complications following trabeculectomy with mitomycin. Arch Ophthalmol. 2002;120:297300.

17. VizzeriG,WeinrebRN. Cataract surgery and glaucoma. Curr Opin Ophthalmol. 2010;21:204.

Lens Surgery in Glaucoma 55

INTRODUCTION

Coexistence of glaucoma and cataract in the same eye is a frequent finding which is mainly due to increasing longevity. It is often challenging to ascertain the most appropriate surgical solution for a visually symptomatic cataract in a glaucoma patient. The factors that most influence decision-making are:• Patient’sage• Glaucomatypeandseverity• Response,toleranceandcompliancewithmedical

therapy• Targetintraocularpressure(IOP). With the technological advances of phacoemulsi-ficationandclear-corneaminimallyinvasiveincisions,theinflammatoryreactionisirrelevant,visualacuityrecovery is fast, and in most cases there are nosignificantIOPchanges.Sincethissurgerydoesnotinvolveconjunctivalmanipulation,theprognosisforanyfiltration surgery that might be needed is not affected. Inopen-angleglaucoma(OAG),wemaychoosetoconductcataractsurgerywhenIOPrespondswelltomedical therapy with one or two drugs and no advanced glaucomatous lesion is present. Accordingtorecentlypublishedstudies,itisexpectedthatthissurgerywilllowerIOPupto2mmHgwithinthefirstyearpostoperatively,andthatIOPwillresumebaseline values after that. In pseudoexfoliative eyes,IOPloweringseemstobemoresignificantaftercataractsurgery.1Inprimaryangleclosure(PAC)andprimaryangle-closureglaucoma(PACG),indicationforcataractsurgery could be earlier and in some cases even the first therapeutic option.

In2006,QuigleyHAandBromanATconductedastudyofOAGandPACGprevalenceusingmodelsconstructedbyage,sex,andethnicity.Theyobtainedthefollowing results:• In2010,therewouldbeanestimated60.5millionpeople with glaucoma. Of these, 74% wouldhave OAG and 26% PACG (Chinese ethnicitypredominates); of the 74%OAG, 55%would befemaleandofthe26%PACG,70%wouldbefemale.

• They also concluded that of cases of bilateralblindness;4.5millionwillbecausedbyOAGand3.9millionbyPACG.

• Proportionally,PACGcausesmuchmorebilateralblindnessthanOAG(10%blindnessinOAGand25%inPACG).2

• PACGprogressionis fasterandmoredestructivethanOAG.

ItisveryimportanttodiagnosePACGatanearlystage and to establish action criteria to prevent its devastating consequences. No matter how much we wish toharmonizeprocedures,no single recommendationappliestoallcases.ThischapterwillfocusonPACandPACG,becauseinmanycasesthispathologyresultsin bilateral blindness.


Inthe2006ConsensusonAngle Closure and Angle- Closure Glaucoma, three stageswere defined in thenatural history of angle closure: 1. Primary angle-closure suspect: Iridotrabecular contactintwoormorequadrants,butnormalIOP,

Maria Reina



opticdiskandvisualfield(VF),withoutevidenceofperipheralanteriorsynechiae(PAS).

2. Primary angle closure: Iridotrabecular contact in twoormorequadrantswitheitherraisedIOPand/orPAS.OpticdiskandVFarenormal.

3. Primary angle-closure glaucoma: Iridotrabecular contact in two or more quadrants plus damage to opticdiskandVF.3

Iridocorneal angle closure occurs when the trabecularmeshworkisblockedbytheirisperiphery,which thus prevents aqueous humor from accessing its main drainage pathway. Anatomically,thisclosurecanbelocatedatseverallevels:• Irisandpupil(pupil-block)• Ciliarybody(plateauiris)• Lens(phacomorphicglaucoma)• Causesbehindthelens(malignantglaucoma).4

The most frequent form of angle-closure glaucoma isbasedonapupillaryblockmechanism(Fig.8.1). Aqueoushumorisproducedinthenonpigmentedepitheliumoftheciliarybody,intheposteriorchamber,flowingouttotheanteriorchamber(AC)acrossthepupil, following an excretion pathway through thetrabecular meshwork in the camerular angle. Increasing age and progressive development of the cataract makes the lens more globus and zonular relaxation slightly advances the lens. If there is an anatomicalpredisposition, thecontactzonebetweentheirisandthelensincreases,hinderingaqueoushumoroutflow. This increases the pressure gradient between theposteriorandanteriorchambers,pushingtheiris

periphery against the trabeculum and creating acute or chronic iridotrabecular contact and glaucoma. Repeatedcontactbetweentheirisperipheryandthetrabeculumleadstotrabeculardysfunction,formationofPAS,IOPincreaseandangle-closureglaucoma. Relative pupillary block is the most frequentangle-closuremechanism(75%ofthecases),butothercausesofclosuremaycoexist.InAsians,anassociationbetween pupillary block and plateau iris seems to be responsibleforthehigherprevalenceofasymptomatic,chronic angle closure.5

Laserperipheraliridotomysolvesthepupilaryblockmechanism,flattenstheirisand,insomecases,openstheangleinPAS-freeareas(Fig.8.2).Ifappositionalangle closure persists, an argon laser peripheraliridoplastycanbeperformed(indicatedinplateauiris). PrimaryangleclosureandPACGaremore frequentin small, hypermetropic eyes with a narrow AC (Fig. 8.3), small cornealdiameter, shortaxial length, inAsiangroups—Chinese,infemalesandwithincreasingage. In nanophthalmic eyes, these characteristics areverymarkedandthereisahigh-riskofPACforanglecongestion.Intheseeyes,surgeryisoftencomplicatedby ciliary block. Nanophthalmos should be suspected inhypermetropymore than8D,cornealdiameter lessthan11mmandaxiallengthlessthan20mmandvery narrowAC. Surprisingly,notalleyeswiththesecharacteristicsdevelopPAC.Factorsotherthananatomicalfeaturesinfluenceangleclosure,suchasirisvolumebehaviorinmydriasis (pharmacological or physiological) andchoroid expansion.6

Fig. 8.1: Pupillary block mechanism Fig. 8.2: Peripheral iridotomy


Treatment of this type of glaucoma has two main purposes:• Topreventprogressionofangleclosure• TocontrolIOPtopreventprogressionofglauco-

matous optic neuropathy. PresenceandextentofPAShavebeenthemainfactors in choosing filtration surgery in such cases,because the greater their extent, the higher theIOP. Studies are under way to assess the effect oflens surgery on PAC progression and PACG (e.g.EAGLE—Effectiveness,inangle-closureglaucoma,oflensextraction). Acuteangleclosureaftercontrollinganacuteeventusing medical therapy7 is a classic indication for laser peripheraliridotomyand/orperipheraliridoplasty.AtleastinAsianeyes,theirefficacyinpreventingrecurringacuteangle-closureeventsandPACGprogressionhasbeen limited, with a 58.1% 4–5-year progression toPACG.Oneadvantageofcataractextractionintheseeyesisthatitimprovesvisualacuity,deepenstheACandwidenstheangle,reducingoreliminatingtheriskofacuteangle-closurerecurrenceandPASprogression,andtheresultingdevelopmentofPACG.8

Studiesarecurrentlyunderwaytoseeifthereisanindicationforclearlensextractionor,atleastforcataractsthatarenotvisuallysymptomatic,inwhichtypeofeyesandwithwhichcharacteristics(EAGLE—Effectiveness,inangle-closureglaucoma,oflensextraction). InPACwith pupillary block,whenPAS greaterthan180°,IOPmorethan24mmHgintheabsenceoftherapyandglaucomatousopticneuropathy,laserperipheraliridectomywillneitherlowerIOPnorrupturePAS.Althoughiridectomyisperformed,lensextractionshouldbeconsidered,associatedornotwithsynechiolysis (ifPASforlessthan1year),toopentheangle,reducecongestion,loweracuteclosureriskandpreventPAS

progression and chronic IOP increase. It should bequestioned whether lens extraction should be performed forthesamereasonsinPASgreaterthan180°,medicallycontrolledIOPbelowmaximumtherapyandsignsofearlyglaucomatousopticneuropathy,inadditiontothealready indicated laser peripheral iridotomy. Cataract surgery should not be indicated without associating filtration surgery in advanced glaucomatous opticneuropathy,IOPmorethan30mmHgandPASgreaterthan270°. In iris plateau syndrome, lens removal does notchange angle-closure risk.3 Peripheral iridoplastyshouldbeperformed,associatedornotwithperipheraliridotomy, depending on whether a pupillary blockcoexists.

CLINICAL EVALUATION OR PATIENT EVALUATION

Every ophthalmology clinic has the equipment needed for a first assessment and diagnosis of suspected angle closure,acuteorchronicclosure,primaryorsecondaryetiology.Besidesclinicalhistoryandthepatient’smoreorlessabundantcomplaints(acuteangleclosure),slit-lampexaminationenablesassessmentofahyperemic,painfuleyewithepithelialedema,increasedIOPandmediummydriasis—acuteclosureevent.Itmayalsoshowacalmeye,inwhichACperipherydepthcanbeimmediatelydeterminedbythevanHerickmethod,aswellasACcentraldepth,presenceofcataract,andirisappearance(Figs8.4AtoD). Comparison of these features with the contralateral eye suggests primary or secondary angle-closure etiology. The anterior chamber depth value is important to identify plateau iris cases due to their normal central depth (> 2.5mm) and narrow periphery, while inPACwithpupillaryblockthecentralvalueislessthan

Fig. 8.3: Narrow anterior chamber, centrally and peripherally


Figs 8.4A to D: Narrow anterior chambers

A B

C D

2.0mm,increasinginprevalenceto85%iflessthan1.5mmwithnarrowperiphery. Anangle-closuresuspectisconfirmedbygonioscopyusingaPosnerlenswithandwithoutindentationandaone-ortwo-mirrorGoldmannlens.ThePosnerlenshasthe additional advantage of enabling ready comparison ofthetwoeyes,checkingwhethertheangleissimilar(Figs8.5AandB). It enables assessment of the degree of angle closure andvisiblestructures,appositionwithiridotrabecularcontactand/orPASandtheirextent.Irisrootfeatures,contour and mobility can also be observed. In spite of being a fundamental examination to define angleopeningandvisiblestructures,theinterpretationof gonioscopy can be subjective and is often difficult. This results both from multiple anatomical variations and from poor technical operation under inadequate conditions.Thereareseveralangleclassifications,some

more complex than others. What is really important istolistvisiblestructures,assesstheminaprimarypositionusinga1mm,narrowbeamof lightofthelowest intensity possible, in a dark environment(AIGS).3The simplified Scheie scheme considers anangle to be open if 360° of pigmented trabeculum is visiblewithout indentation, and to be a primary“narrow” angle when the upper or the lower half of pigmentedtrabeculumcannotbeseen.Suchanarrowangle could be liable to occlusion if we are able to view thepigmentedtrabeculumwithaGoldmannlenswhenthepatientislookingatthegonioscopymirror;ontheother hand the angle can be closed due to apposition or to synechiae.9

Gonioscopicangleassessmentissubjectiveandpronetoerrorsofoperationandinterpretation.However,itisvery important to choose the most appropriate therapy for each case.


Subsequently,therehasbeenanattempttoincreaseobjectivity in biometric parameter assessment for theanteriorsegmentandanteriorchamberanatomy, using:• Ultrasound biomicroscopy (UBM):Studiesangleandanteriorsegment,withtheadvantageofenablingviewing of structures posterior to the iris, suchas the ciliary body, zonule and anterior choroid.Angle behavior can be studied with or withoutillumination. It is quite useful for studying plateau iris.Disadvantagesinclude:requiresanimmersioncup in contact with the eye, which needs greatpatient cooperation; it is performed in supineposition; risk of superficial corneal lesion andinfection;itmayinadvertentlydistorttheangle;andit takes a long time. It requires a lot of training.10

• PENTACAM (Scheimpflug image): It studies anterior segment biometry, namelyAC depth, with goodreproducibility(Figs8.6AandB).Itdoesnotletussee either the whole angle or structures posterior to the iris.Sinceitcannotreferenceorlocatethescleralspur,angle measurements are not very accurate. It requires lightforimagecollection,whichmayunderestimateanglenarrowing.Itisanoncontact,easyandquickmethod,inwhichtheimageiscollectedwiththepatient in a sitting position.10

• AS-OCT or SL-OCT:Thisisaquick,noncontactexamination that provides high-resolution images. It does not require light for image acquisition and assesses important anterior segment parameters. It has been showing good sensitivity in detecting closed angles. It requires manual scleral spur location for anglestudy,althoughthis isnotpossible in25%

of cases. It does not allow us to view structures posterior to the iris. Among new risk factorsfor angle closure that may be studied by this technology are: anterior chamber width as measured horizontally fromspur to spur;anteriorchamberareaandvolume;iristhickness,areaandcurvature.Thelensvaultcanbeassessedbythistechnology,as well as other anatomical features which seem to have an important role in the pathogenesis of this kind of glaucoma.4 It allows estimation of the trabeculo-irissurfacearea(TISA),anglerecessarea(ARA) and the angle opening distance (AOD)10 (Figs8.7and8.8).

• Ultrasound: To measure axial length and estimate the intraocular lens.

• Specular Microscopy: Endothelial cell population should be assessed before cataract surgery because itmaybeseverelycompromised,especiallyincaseofprioracuteangle-closureevents(<500cells/mm2).

• Visual Fields: To assess glaucomatous optic neuropathy.

DESCRIPTION OF SURGICAL TECHNIQUE, DIFFICULTIES AND THEIR RESOLUTION

Mostpatientsundergosurgeryundertopicalanesthesia,butthechoiceshoulddependonthesurgeon’sjudgmentandbearinmindthepatient’sprofile. PreoperativepreparationisimportantineyeswithnarrowAC.Intraocularpressureshouldbekeptlowby topical administration of hypotensive eye drops,by oral acetazolamide, or by intravenousmannitoladministration 30minutes before the patient entersthe theater.

Figs 8.5A and B: Closed angle

A B


Fig. 8.6A: Closed angle before and after phacoemulsification. Prephacoemulsification: AC vol. 74 mm3, ACD 1.40 mm, angle 17.8°

Fig. 8.6B: Closed angle before and after phacoemulsification. Postphacoemulsification: AC vol. 117 mm3, ACD 3.08 mm, angle 35°

Fig. 8.7: Anterior chamber area (ACA). AC angle 20° (500 microns from the spur)Courtesy: Maria da Luz Freitas

Fig. 8.8: AC depth (ACD), AC width (ACW), AC volume (ACV), pachymetry, anterior lens curvature, iris thickness, area and volume, pupillary diameterCourtesy: Maria da Luz Freitas

Preoperativeocularglobecompressionmaneuversshouldbeperformedcarefullyandonly ifnecessary,bearing in mind the presence of glaucomatous optic neuropathy. Clear corneal incision is performed, followed byfilling of the anterior chamber with viscoelastic material

(Fig. 8.9).The level ofdepthobtained is assessed, aswell as the need to use denser substances to keep a deepanteriorchamberisascertained.Bearinmindthepotential for endothelial cell loss caused by acute angle-closureevents.Viscoelasticmaterialshouldbeinjecteduntil there is slight reflux through the entry port.


Inamioticpupilwithposteriorsynechiae,diameteris increased by injecting viscoelastic material towards pupiledges,eliminatingposteriorsynechiae(Fig.8.9). Next,anotherportismadeatapproximately90° from the main incision. If the pupil needs further dilation, this can be performedmechanically usingtwohooks180° apart and pulling the pupil edges in various directions. These maneuvers may cause slight bleeding, whichwill be flushed or aspirated duringphacoemulsification. Pupil diameter is then reassessed by reinjectingviscoelasticmaterial. Iris retractors (twoor four,asneeded)orpupillarydilationringsmaybeused,orsmallsphincterotomiescanbeperformedwithaVannasscissors. Ontheotherhand,anatrophic,partially-mydriaticiris due to previous acute angle-closure events will tend toprolapsethroughcornealincisions(Fig.8.10). Inthiscase,theincisionshouldbemorecorneal,more anterior and longer to avoid prolapse and maintain anterior chamber stability. Iris manipulation should becareful,because theblood-waterbarrier is easilyaltered and an inflammatory reaction can be induced inthepostoperativeperiod,requiringmorefrequentadministration of a topical steroid.11

Filling the anterior chamber with viscoelasticmaterial is very useful for endothelial protection,anteriorchambermaintenance,andbecauseitdisruptsposterior synechiae and opens the camerular angle by disruptingrecentPAS(<1year). Capsulorhexis is initiated with a cystotome and shouldbebetween5and6mmindiameter.Sometimes,the anterior chamber is so narrow that the cystotome

must enter the anterior chamber horizontally until it reachesthecentralpartoftheanteriorcapsule,whereitis changed to a vertical position to initiate a continuous curved path until it is removed, with or without acapsulorhexisforceps(Fig.8.11). Inpatients,whohaveanarrowanteriorchamberand inwhomthe lensoftenshowsmarkedvaulting,capsulorhexistendsto“escape”,especiallywhenthereiscoexistingpositivepressure.Here,usingaviscoelasticmaterial of higher viscosity helps to maintain anterior chamber depth and capsulorhexis can proceed safely (Fig.8.12). Bothhydrodissectionandhydrodelaminationshouldbe slow and progressive so as to keep the nucleus inside the capsular sac. Phacoemulsification should be performed withthe usual parameters (flow and vacuum) in orderto maintain anterior chamber and posterior capsule stability,therebyavoidingchamberdepthfluctuationsand thus preventing posterior capsule rupture. It is important to keep the phacoemulsification tip inside the sac or on the iris plane to minimize corneal endotheliumthermallesionsorviscoelasticloss,alwaystakingcarewiththeposteriorcapsule(Fig.8.13). Anteriorchamberdepthcanbecontrolledbyvaryingsalinebottleheightandincreasingitasnecessary,tominimize posterior capsule fluctuations. The capsular sac is filled in with viscoelastic materialandanintraocularlens(IOL)isinsertedinthesac.Then,mostofviscoelasticmaterialisremovedto avoid postoperative hypertensive peaks.

Fig. 8.9: Widening of the pupil with viscoelastic material and filling the anterior chamber until reflux is obtained

Fig. 8.10: Atrophic iris


Fig. 8.11: Narrow anterior chamber Fig. 8.12: Capsulorhexis

Fig. 8.13: Phacoemulsification tip at the iris plane

In posterior capsule disruption with vitreous outflow, aminimal vitrectomy should be performedto carefully remove the remaining cataract material to decreaseinflammatoryreaction.Inasmalldisruption,trytoplacetheIOPinsidethesac.Inalargedisruptionwith conserved anterior capsule, attachment at theciliary sulcus should be chosen. The pupil may be contracted by the intracamerular useofMiochol (acetylcholine) tokeep the irisawayfromtheentryport,ifnecessary. Entryportsarehydratedandantibiotic(cefuro-xime)isinjectedintotheanteriorchamber.Surgicalwound leakproofness is checked with microsponges (Fig.8.14). Afterremovingtheblepharostat,itmustbecheckedthat the anterior chamber remains deep and stable.

Fig. 8.14: Hydration of entry ports

Antibiotic, steroid and anti-inflammatory non-steroidal eye drops should be administered postopera-tivelyfourtimesaday,unlesssurgeryhasinvolvedirismanipulation or other complications that may lead us to expect an inflammatory reaction.

IMMEDIATE POSTOPERATIVE COMPLICATIONS AND RESOLUTION OF COMPLICATIONS

The most frequent postoperative complications of this surgery are inflammation and IOP increase.Both result from iris manipulation, difficulties inphacoemulsification and incomplete removal of viscoelastic material. They are usually controlled withtopicalsteroidadministrationandtopicaland/orsystemicocularhypotensiveagents.Insomecases,filtration surgery may be needed for tension control.


When the corneal endothelial cell population is much depleted,therewillbeanadditional2–12%cell lossincataractsurgery,whichmaycausedecompensation.Topical corticoid therapy and hyperosmotic eye drops help to balance the cornea. There can be hyphema in the postoperative period due to iris stretching maneuvers or sphincterotomies. In general, it reabsorbs in a fewdays and it rarelyrequires anterior chamber flushing. In nanophthalmos, the anterior segment is verynarrowandcataractsurgerycould/shouldbeplannedwith pars plana vitrectomy. These eyes are often complicated by edema and choroid bleeding.

REMARKS

The lens has an important role in the pathophysiology of acute camerular angle-closure events and primary angle-closure glaucoma. Such eyes have a narroweranterior chamber, lower anterior chamber volumes,shorter axial length and more globus and more anterior lens than normal eyes. This is the main mechanism of relative pupillary block which occurs in these cases. Lensextractionpreventsoratleastseemstoreducethe risk of acute angle-closure recurring and the risk of progressiontoPACG,evenintheabsenceofvisuallysymptomaticcataracts,byeliminatingthismechanism,deepeningtheanteriorchamber,wideningthecamerularangleandpreventingformationorprogressionofPASin the angle. The exact role of and the best timing for lens extractionneed tobeascertained, andongoingstudies are addressing those questions. RatesofpatientswithPACGhavestartedtodeclineinrecentyears,afteralongperiodofincreasesinratesof patients undergoing cataract surgery. Althoughotherexplanationsarepossible,thislendssupporttothe hypothesis that cataract surgery may reduce the likelihood of acute angle closure.12

REFERENCES

1. VizzeriG,WeinrebR.Cataract surgeryandglaucoma.CurrOpinOphthalmol.2010;21:20-4.

2. QuigleyHA, BromanAT. The number of people withglaucomaworldwidein2010and2020.BrJOphthalmol.2006;90:262-7.

3. FriedmanDS,WeinrebRN.ConsensusonAngle-closureand Angle-closure Glaucoma. AIGS/WGAConsensusSeries; 2008.TheNetherlands:Kugler Publication.RefType:Report.

4. SharmaT,LowS,FosterPJ.Theclassificationofprimaryangle-closureglaucoma.In:GrehnF,StamperR(Eds).EssentialsinOphthalmology:Glaucoma.Berlin:Springer-Verlag;2009.pp.41-8.

5. NongpiurME,KuJYF,AungT.Angleclosureglaucoma:amechanistic review. CurrOpinOphthalmol. 2011;22: 96-101.

6. QuigleyHA.Angle-ClosureGlaucoma—SimplerAnswerstoComplexMechanisms:LXVIEdwardJacksonMemorialLecture.AmJOphthalmol.2009;148(5):657-69.

7. LamDS,LungDY,ThamCC,etal.Randomizedtrialofearly phacoemulsification versus peripheral iridotomy to prevent intraocular pressure rise after acute primary angle closure.Ophthalmol.2008;115:1134-40.

8. LamDS,LungDY,ThamCC,etal.Currentapproachesto the management of acute primary angle closure. Curr OpinOphthalmol.2007;18:146-51.

9. KessingSV,ThygesenJ.DiagnosticmethodsinPAC.In:PrimaryAngle-closureandAngle-closureGlaucoma.TheNetherlands:KuglerPublications;2007.pp.11-47.

10. FriedmanDS,HeM.Anteriorchamberangleassessmenttechniques.SurOphthalmol.2008;53(3):250-73.

11. SharmaT,GazzardG, BartonK.Management of thedifficultcataractinglaucomapatients.GlaucomaTopicsand Trends—Glaucoma and Cataract. A ContinuingMedicalEducationPublication.Quarter2.2008—issue10.Consulted in February 2011. Available at http://www.glaucomatopics.com/

12. KeenanTD,SalmonJF,YeatesD,etal.Trendsinratesofprimary angle closure glaucoma and cataract surgery in Englandfrom1968to2004.JGlaucoma.2009;18:201-5.

Nikki

Typewriter


Hyperfiltration 53Hypertonic hypothalamia 5Hypertony 5Hyphema 4, 5, 31, 45, 53Hypothalamia 5 with ocular hypertony 5Hypotonic hypothalamia 5 maculopathy 5Hypotony 4, 5, 20, 31, 45, 53

I

Implant expulsion 21 in scleral lake 52f projection over iris 12fIncreased intraocular pressure 31, 46Intraluminal stent 19Intraocular infection 6 lens 50, 61 pressure 1, 14, 23, 40, 48, 53, 55Intrascleral lake 24f space 43Iridectomy 3Iridocorneal endothelial syndrome 25, 37Iridotrabeculodescemetic synechiae 46fIris and pupil 56 thickness 60f

J

Juvenile glaucoma 4Juxtacanalicular trabeculum 33

K

Kelly punch 51Keratoplasty 16, 19Kocher’s forceps 2Krupin device 14 valve 15

L

Lacrimal duct obstruction 49Late hypotony 6 tube erosion 21Lateral flap 18Lens surgery in glaucoma 55Lenticular contact 20

Lidocaine 2Limbal base flap 18 thinning 16Limbus-based scleral flap 52fLow anterior chamber 31, 45

M

Maculopathy 20Malignant glaucoma 21, 56Mean intraocular pressure 35Mermoud forceps 26, 41Mini-crescent angled knife 26, 40 blade 10Minimally invasive surgery 8Mitomycin C (MMC) 4, 10, 16, 50

N

Narrow angle glaucoma 25, 37 anterior chamber 57f, 58f, 62fNeodymium:yttrium-aluminum-garnet 29Neovascular glaucoma 4, 25, 37Nonpenetrating deep sclerectomy 49Nonsteroidal anti-inflammatory drugs 50Nonvalved implants 19

O

Occlusive sutures 20Ocular hypertension 6, 45, 53Open angle glaucoma 48, 55Opening of conjunctiva 2 Schlemm’s canal opening 40Ophthalmic viscosurgical device 53Optical coherence tomography 38Oral anticoagulants 49

P

Pachymetry 60fParkinson’s dementia 50Peeling of Schlemm’s canal 52fPentacam 59Perforation of trabeculodescemetic window 30, 44Peripheral iridectomy with scissors 3fPhacoemulsification 60fPhacomorphic glaucoma 56Pigmentary glaucoma 9Plate insertion and fixation 18Plateau iris 25, 37, 56Platelet antiaggregation 49Posterior drainage devices 14

Postphacoemulsification 60fPrephacoemulsification 60fPresence of silicone oil 16Primary angle closure 56 glaucoma 55, 56 open angle glaucoma 25, 37Proliferative vitreoretinopathy 21Proximal obstruction 20Pseudophakic eye 5Pupillary block 1 mechanism 56f

R

Recurring uveitis 16Reduced visual acuity 31, 45Refractory acute hypertensive event 1Retinal detachment 21Risk of trabeculectomy 1

S

Scheimpflug image 59Schlemm’s canal 1, 26, 29, 35, 37, 40-44 dilation 41fScissors 3fScleral dissection 38 flap 2, 10f, 40 dissection 43 secured with a W-shaped suture 39fSclerectomy 3, 3fScleromalacia 2Secondary open angle glaucoma 25, 37Semicircular opening of conjunctiva 2fSilicone and polypropylene Ahmed valves 16fSmall Descemet’s membrane 46fSponge with MMC 11fStrabismus 21Sturge-Weber syndrome 24, 25Subconjunctival filtration lake 12fSub-Tenon’s dissection 51 space 8Superficial scleral flap after closure 29f dissection 40 suture 52fSuprachoroidal hemorrhage 6Surgical complications of trabeculectomy 5tSuture exposure in anterior chamber 46

Index 67

T

Tenectomy 26f

Tension assessment 42f

T-flux NV implant 29f

Tiny hyphema 35f

Trabecular micro-bypass stent implantation 33

Trabeculectomy 1, 1t, 2t, 4t

Trabeculodescemetic window 41f, 43f

Trabeculotomy 1

Traumatic glaucoma 4

Tube covering 18 insertion 18 in pars plana 19 in posterior chamber 19 retraction 20Two-stage surgery 19Types of anesthesia 17

U

Ultrasound biomicroscopy 25, 38, 59Unroofing of Schlemm’s canal 27fUveitic glaucoma 4

Uveitis 53 glaucoma hyphema syndrome 50

V

Vannas scissors 3, 61Venturi system in Ahmed valve 15fVitreous humor 20 loss 4, 5

W

W-shaped corneal suture 26f

Health & Medicine

Adult glaucoma surgery da luz, freitas maria [srg]