Adult glaucoma surgery da luz, freitas maria [srg]

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD
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Foreword
Matthias C Grieshaber
Guests
João Eurico Lisboa MD
Ex-Chairman
Department of Ophthalmology
Hospital Santo António dos Capuchos
Lisbon, Portugal
Queiroz Marinho MD
Ex-Chairman
Hospital Geral de Santo António
Porto, Portugal
Editor
Maria da Luz Freitas MD
Consultant
Hospital da Arrábida
Porto, Portugal
Adult
Glaucoma Surgery

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Adult Glaucoma Surgery
First Edition: 2013
ISBN: 978-93-5090-355-1
Printed at:
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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-Chairman
Hospital Santo António dos Capuchos
Lisbon, Portugal
Reminiscences

Open Angle Glaucoma
If 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 Glaucoma
We 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 Aphakics
Cyclodialysis 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 Glaucoma
In 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 Glaucoma
A 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-Chairman
Hospital Geral de Santo António
Porto, Portugal

Manuela Carvalho MD
Hospital Graduate Assistant
in Ophthalmology, Lisbon, Portugal
Arabela Futre Coelho MD
Instituto Oftalmológico
Dr Gama Pinto (IOGP), Lisbon, Portugal
Pedro Faria MD
Hospital Assistant
Centro de Responsabilidade
Integrada de Oftalmologia do Centro
Hospital Universitário de Coimbra (CHUC)
Coimbra, Portugal
Teresa Gomes MD
Centro Hospitalar de Lisboa
Central (CHLC)
Lisbon, Portugal
Maria Reina MD
Centro Hospitalar de Lisboa Central (CHLC)
Lisbon, Portugal
Contributors
A Rodrigues Figueiredo MD
Consultant
Hospital de Santa Maria (CHLN) and
Lisbon School of Medicine
Lisbon, Portugal
Maria da Luz Freitas MD
Consultant
Hospital da Arrábida
Porto, 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 Physician
University of Basel
Switzerland
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 penetrating,
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
– 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
• Indications 24
– Strictu Sensu 24
– Relative Contraindications 25
– Absolute Contraindications 25
• Patient's Assessment 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
• Indications 37
• Relative Contraindications 37
• Absolute Contraindications 37
• Patient's Assessment 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
• Patient's Clinical Evaluation 49
• Surgical Technique amd Complications 50
8. Lens Surgery in Glaucoma 55
Maria Reina
• 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’s life expectancy
• Disease progression rate
• Risks and benefits of alternative therapies
• Risk/benefit of trabeculectomy
Table 1.2: Indications for trabeculectomy
• Failure of medical and surgical therapies to control
progressive disease
• When the usual medical alternatives are not expected to
succeed (young patients, very high IOP, very advanced
disease)
• Refractory acute hypertensive event
• Congenital glaucoma (combined with trabeculotomy)
Pedro Faria
Trabeculectomy
1

 Adult Glaucoma Surgery2
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: Relative contraindications for trabeculectomy
• Previous trabeculectomy failure
• High risk of failure
• High risk of surgical complications
• When potential vision loss dramatically affects quality of life
(single eye/potential loss of professional activity)
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: Complications from the use of antimetabolites
in trabeculectomy
• Cystic and thin-walled blebs (with leaks)
• Hypotony and its complications
• Blebitis and endophthalmitis
Table 1.5: Indications for the use of antimetabolites in
trabeculectomy
• Uveitic glaucoma
• Neovascular glaucoma
• Traumatic glaucoma/previous surgery
• Congenital and infantile/juvenile glaucoma

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: Surgical complications of trabeculectomy
Intraoperative Immediate Postoperative Late
Hyphema Hypotonic hypothalamia Hypotony
Athalamia Hyphema Cystic bleb
Conjunctival damage Choroidal bleeding Blebitis
Vitreous loss Choroidal detachment Endophthalmitis
Expulsive hemorrhage Hypotonic maculopathy Hypotonic maculopathy
Hypertonic hypothalamia Cataracts
Blebitis/Endophthalmitis
Hypertony
Encapsulated bleb

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.

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-
borative Initial Glaucoma Treatment Study (CIGTS)
comparing initial treatment randomized to medi
cations or surgery. Ophthalmology. 2001;108:1943-53.

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
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

 ExPressTM
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 with
formation 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 resolved
with the usual procedures: cycloplegic drugs, anti-
inflammatory drugs, rest and potential surgical
decompression in more severe cases.
• Hypertony as a consequence of excessive viscoelastic
solution 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 a
worse prognosis, subconjunctival antimetabolites
may be associated intraoperatively (MMC) or

 ExPressTM
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 valve
Source: Br J Ophthalmol 1998;82:1083-9. Perspective Glaucoma
drainage devices; past, present and future
Manuela Carvalho
Posterior
Drainage Devices 3

 Posterior Drainage Devices 15
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
• Previous failed MMC trabeculectomy
• Active neovascular processes
• Active or recurring uveitis
• Iridocorneal syndromes
• Epithelial ingrowth of anterior chamber
• Bullous keratopathy with an indication for
keratoplasty
• Associated vitreoretinal surgery
• Presence of silicone oil
• Anterior synechiae
• Developmental glaucomas associated with angle
anomalies.
Eyes in Which Trabeculectomy is Technically Not
Possible or Has a High-Risk of Intraoperative
Complications
• Extensive conjunctival scarring
• Limbal thinning.
Patients in Whom Trabeculectomy With MMC
Has a Very High-Risk of Postoperative
Complications
• Contact lens wearers
• Lid margin changes
• Previous history of blepharitis
• Patients who live in dirty and/or dusty environments
• Risk of suprachoroidal hemorrhage.
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
• Borderline endothelial count
• Strict patient compliance with postoperative visits
is not possible.
PREOPERATIVE ASSESSMENT
Preoperative assessment is crucial to surgery success.
Therefore, the following must be taken in consideration:
• Conjunctival status, testing conjunctival mobility
and extent of any scarring.
• Iris study to detect any neovascularization that may
predispose to intra- or postoperative hyphemas and
indicate previous antiangiogenic therapy.
• Analysis of anterior chamber depth to assess
potential risk of tube contact with the endothelium.
• Gonioscopy to assess the presence and location
of synechiae, neovessels, and angle closure to
help choosing which quadrant to use (preferably,
the superior temporal quadrant for easier plate
placement).
• Lens status, because combined surgery should be
considered if cataracts are present.
• Presence of aphakia in a vitrectomized eye with
potential pars plana tube insertion.
• Presence of pseudophakia with potential insertion
of a tube in the ciliary sulcus.
• Presence of vitreous humor in the anterior chamber,
indicating anterior chamber vitrectomy or potential
posterior tube insertion.
• Presence of silicone oil, indicating device implantation
in an inferior quadrant.
• Predicted associated vitreoretinal surgery (e.g. usage
of pars plana clips).
• Predicted future penetrating keratoplasty (better
results 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.
• Previous inflammation should be reduced as much
as possible to reduce the postoperative scarring
response.
• Control of potential hypertension, thereby
decreasing 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:
• Skin disinfection with 10% povidone
• Eye surface and conjunctival fornix disinfection with
5% povidone
• Sterile plastic drapes, isolating lid margins
• Blepharostat, preferably rigid (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-base flap
• Lateral flap
• Free graft flap.
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
• Greater thickness for tube protection.
Disadvantages
• Variable thickness (potential Dellen)
• Complete sterilization not guaranteed
• Potential for immune reaction.
Dura Mater, Pericardium, Fascia Lata
Advantages
• Processing by dehydration and gamma sterilization
prevent HIV and variant Creutzfeldt-Jakob
transmission
• Eliminates cell presence, thereby preventing auto
immune reaction
• Longer-lasting (5 years)
• Storage at room temperature
• Easy handling.
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.
• Angle closure and very narrow anterior chamber,
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
• In aphakic and fully vitrectomized eyes, or in which
associated vitreoretinal surgery is foreseen.
• History of predicted keratoplasty: A pars plana
clip (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
nonvalved implants (with 20–30%) than in the Ahmed
valve (8–10%).15
It may lead to:
• Athalamia
• Endothelial contact
• Cataracts (lenticular contact)
• Choroidal detachment
• Hemorrhagic choroid detachment
• 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
• Vitreous humor (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
• Acquired Brown’s syndrome (superior oblique).
The resolution involves prisms, strabismus surgery,
implant extraction and placement of another smaller
implant in another quadrant.
Other Complications of Glaucoma Surgery
• Retinal detachment
• Proliferative vitreoretinopathy
• Malignant glaucoma.
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
Table4.1: Deepsclerectomy—advantagesandmechanisms
Advantages • Minimally invasive, nonpenetra
ting surgery
• Does not penetrate the anterior
chamber
• Controlled aqueous humor
outflow
• Fewer intra- and postoperative
complications
• Faster recovery
• Flatter blebs
Main drainage mechanism • Subconjunctival pathway
Adjuvant mechanisms • Uveoscleral pathway
• Conventional pathway
Fig. 4.1A: Filtration bleb 1 year after surgery Fig. 4.1B: Intrascleral lake, 1 year after DS with aquaflow implant
Source: 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 • Primary open-angle glaucoma
• Secondaryopen-angleglaucoma
• Glaucoma in high myopia
• Advanced glaucoma
• Glaucoma associated with
Sturge-Weber syndrome
• Glaucoma in nanophthalmos
Relative contraindications • Narrow-angle glaucoma or
plateau iris
• Glaucoma secondary to angle
anomalies: ICE, congenital and
juvenile
Absolute contraindications • Absolute glaucoma
• Angle recession
• Neovascular glaucoma
• Chronic closed-angle glaucoma
Fig. 4.2B: Open-angle, without contraindication for deep sclerectomy
Source: SL-OCT (Heidelberg Engineering)
Fig. 4.2A: Narrow-angle, contraindicated for sclerectomy
Source: SL-OCT (Heidelberg Engineering)

Adult glaucoma surgery da luz, freitas maria [srg]

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