Glaucoma Surgery

P. Bettin, P. T. Khaw, F. Bandello

• Publisher: S. Karger
• Year: 2012
• Print ISBN: 9783805599375
• eBook ISBN: 9783805599382
• Topic: Medicine
• Subtopic: Biotechnology in Medicine

In this volume of Developments in Ophthalmology, a panel of renowned glaucoma surgeons reports its findings and the updated evidence-based literature data on indications, outcomes, pearls and pitfalls of techniques in which they all have an undisputable 'hands-on' everyday experience. The publication begins with chapters on conventional procedures, i.e. trabeculectomy (still the gold standard), deep sclerectomy, and glaucoma drainage device implantation explicitly focusing on postoperative management. The role of the ocular surface in glaucoma surgery and the issue of wound healing and its modulation through antimetabolites are further discussed. In the second part, the attention shifts to new techniques which still have a marginal role, but are promising for particular indications. In the last part, the greatest challenges of glaucoma surgery such as the surgical approach to angle closure, concomitant glaucoma and cataract as well as pediatric glaucoma are discussed in detail. Finally, the last chapter is dedicated to cyclodestructive techniques.This volume is recommended to glaucoma surgeons and glaucoma specialists seeking information on the best therapy for their patients, but also to general ophthalmologists who refer their patients for surgery or follow them up afterwards.

Bettin P, Khaw PT (eds): Glaucoma Surgery. Dev Ophthalmol. Basel, Karger, 2012, vol 50, pp 1-28

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Enhanced Trabeculectomy – The Moorfields Safer Surgery System

Peng Tee Khaw^a,b · Mark Chiang^a,f · Peter Shah^a,b,c,d · Freda Sii^a,b,c · Alastair Lockwood^a,e · Ashkan Khalili ^a,e

^aNational Institute for Health Research Biomedical Research Centre, Moorfields Eye Hospital and UCL Institute of Ophthalmology, ^bEyes and Vision, UCL Partners Academic Health Science Centre, London, ^cUniversity Hospitals Birmingham NHS Foundation Trust, Birmingham, ^dCentre of Health and Social Care Improvement, School of Health and Wellbeing, University of Wolverhampton, Wolverhampton, ^eUCL School of Pharmacy, London, UK; ^fDepartment of Ophthalmology, Royal Brisbane and Women's Hospital, Brisbane, Qld., Australia

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Abstract

Trabeculectomy with anti-fibrotic treatment is still the most popular incisional procedure for glaucoma filtration surgery (GFS) worldwide. The advent of anti-fibrotic agents reduced failure due to scarring but resulted in increased complications. Advances in trabeculectomy surgery have been driven by the need to minimise the risk of: (1) complications and (2) surgical failure. This chapter covers preoperative, intraoperative and postoperative strategies, which improve the outcome of GFS. Strategies to reduce the risk of complications centre on the prevention of postoperative hypotony by minimising the risk of overdrainage, postoperative wound leaks and poor bleb morphology. Surgical techniques to reduce the risk of postoperative fibrosis by the use of anti-fibrotic agents (including mitomycin C) are discussed in detail. These techniques are based on a combination of considerable clinical experience, observation and laboratory research. The need to address pre-, intra- and postoperative issues in each individual patient is emphasised. These changes are embodied in the system we call the ‘Moorfields Safer Surgery System’. The use of these strategies has considerably reduced the incidence of major complications including hypotony, cystic blebs and endophthalmitis in practices around the world. Most of these techniques are simple, require minimal equipment and can be easily mastered. They are associated with an improvement in overall outcome and it is hoped that this chapter will help the reader benefit from these advances.

Copyright © 2012 S. Karger AG, Basel

Trabeculectomy, first introduced in the 1960s, has become the gold standard for many types of glaucoma and is still the most commonly performed glaucoma filtration surgery (GFS). The operation of trabeculectomy aims to create a permanent drainage outflow channel for aqueous humour, connecting the anterior chamber (AC) to the sub-Tenon's space. Failure of trabeculectomy can occur as a result of scarring at the site of the new drainage channel with subconjunctival fibrosis and scarring at either the level of the scleral flap or the ostium. However, traditional trabeculectomy surgery has previously been associated with a significant risk of complications including vision-threatening hypotony, bleb-related problems and endophthalmitis. Recently, based on clinical observation and experimental research, simple but significant modifications to the original trabeculectomy techniques have evolved, which have considerably improved the success rates and reduced the complication rates of trabeculectomy, some of which have been embodied in a system we evolved known as the Moorfields Safer Surgery System.

The advent of trabeculectomy revolutionised GFS compared to previous full-thickness procedures [1]. The original description of trabeculectomy involved the use of a superior rectus suture, a limbal-based conjunctival flap (LBCF) and a deeper scleral flap with pre-placed sutures. The aim of the operation at that time was to excise a block of Schlemm's canal and trabeculum, allowing free aqueous drainage into the exposed ends of the canal of Schlemm, hence the name trabeculectomy. Originally, it was never intended to make a fistula to result in a drainage bleb, which is interesting bearing in mind that in the initial concept there was no drainage bleb with contemporary nonpenetrating surgical techniques. However, the presence of a drainage bleb tended to be associated with an increased success rate. Trabeculectomy then began to be regarded as filtration surgery, and more attention was focused on surgical techniques, which facilitated the creation of diffuse drainage blebs.

The advances in trabeculectomy were driven by the need to minimise the risk of: (1) complications, including postoperative hypotony, infection and bleeding, by preventing overdrainage, postoperative wound leaks and poor bleb morphology, and (2) surgical failure, by reducing postoperative fibrosis (using anti-fibrotic agents).

The variation in the current practice (preoperative strategies, intraoperative techniques and postoperative management) of GFS, diverse case-mix and different success criteria account for the variable results published in the literature, with ‘success’ rates ranging from 71 to 100% [2-11]. In the Tube Versus Trabeculectomy (TVT) study, the cumulative probability of failure in the trabeculectomy group was 30.7% at 3 years [4]. However, high success rates and low complication rates can be achieved when meticulous attention to preoperative risk stratification, intraoperative techniques and postoperative management is employed. Our success rate with mitomycin C (MMC)-augmented trabeculectomy is 96.7% [intraocular pressures (IOP) ≤21 mmHg] at 3 years in a complex case mix. [10]. Other surgeons using our system on lower risk patients have had good success rates with 100% IOP <21 mmHg and low complication rates such as flat AC (1.8%) and hypotony (1.5%) [11].

This chapter covers the intraoperative techniques of GFS and specific strategies to minimise the risk of intra- and postoperative complications. Postoperative management, as well as the management of postoperative complications, is covered in other chapters.

Surgical Technique

Filtration Area Positioning

GFS should be performed superiorly, fully protected by the upper lids. A peripheral iridectomy placed at 12 o'clock is also covered by the lid, and does not give rise to diplopia. Interpalpebral or lower fornix drainage blebs have up to a 10 times greater incidence of inflammation and endophthalmitis, particularly if anti-fibrotic agents are used (fig. 1). Recurrent subconjunctival haemorrhage has been reported more commonly with inferior drainage blebs, together with bleb discomfort and pain. It is important to position the bleb with maximal upper lid coverage. Other surgical procedures such as tube drainage surgery should be considered if this is not possible.

Corneal Traction Suture

Superior rectus traction sutures may cause globe perforation, retrobulbar haemorrhage, postoperative ptosis, superior rectus haematoma and subconjunctival haemorrhage. Subconjunctival haemorrhage or superior rectus haematoma may trigger an excessive wound healing response in trabeculectomy. The use of superior rectus traction sutures was associated with reduced trabeculectomy success in the CAT152 antibody trial [12]. The corneal traction suture technique [13, 14] reduces the potential conjunctival damage and bleeding caused by a superior rectus traction suture. The vector force of the corneal suture is superior to that achieved with a superior rectus suture. The disadvantages of the corneal traction suture include the small risk of placing the ...

Table of contents

• Cover Page
• Front Matter
• Enhanced Trabeculectomy – The Moorfields Safer Surgery System
• Deep Sclerectomy
• Glaucoma Drainage Implant Surgery
• Postoperative Management of Penetrating and Nonpenetrating External Filtering Procedures
• Ocular Surface and External Filtration Surgery: Mutual Relationships
• Wound Healing and Glaucoma Surgery: Modulating the Scarring Process with Conventional Antimetabolites and New Molecules
• Mini-Drainage Devices: The Ex-PRESS Mini-Glaucoma Device
• Laser-Assisted Techniques for Penetrating and Nonpenetrating Glaucoma Surgery
• Ab externo Schlemm’s Canal Surgery: Viscocanalostomy and Canaloplasty
• Ab interno Schlemm’s Canal Surgery: Trabectome and I-Stent
• Surgical Treatment of Angle-Closure Glaucoma
• Management of Concomitant Cataract and Glaucoma
• Surgical Management of Pediatric Glaucoma
• When Should We Give Up Filtration Surgery: Indications, Techniques and Results of Cyclodestruction
• Subject Index