Glaucoma management 2016

CURRENT GLAUCOMA
MANAGEMENT 2016
MEDICAL , TRAB, VALVES
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DR DINESH MITTAL DR SONALEE MITTAL
DRISHTI EYE HOSP VIJAYNAGAR INDORE

Central Corneal Thickness and
Tonometry
• one can take far better care of patients simply by
categorizing corneas as ‘thin,’ ‘average,’ or ‘thick,’
just as it is important to recognize that optic discs
come in ‘small,’ ‘medium,’ and ‘large,’ allowing the
clinician to interpret disc configurations
accordingly. Measuring CCT leads to the
discontinuation of therapy in many overtreated
ocular hypertensives and escalation of therapy in
patients with thin corneas in whom control is
clearly inadequate.

Preoperative Evaluation and
Diagnostic Approach
• The importance of a good history-taking, proper
clinical examination and a thorough baseline, pre-
operative diagnostic testing are of paramount
importance when planning for surgery. It can both
guide the physician to a tailor-made surgical approach
and also be invaluable after surgery by providing a
proper baseline for the post-operative management
period. The detailed analysis of the patient’s risk
factors for surgical failure are thus of extreme clinical
importance for the clinician when planning for surgery.
Furthermore, it cannot be overstressed how these risks
and possible outcomes should be made clear to the
patient when obtaining the appropriate informed
consent.

Preoperative Conjunctival Health
and Trabeculectomy Outcome
• Chronic insult to the conjunctiva can result in ‘priming’ of
the conjunctival cellular profile, potentially resulting in an
augmented postoperative fibrotic response following
trabeculectomy and higher surgical failure rates. Previous
chronic use of topical glaucoma therapy is associated with
a proinflammatory conjunctival cellular profile, with
significantly more fibroblasts, macrophages, and
lymphocytes present in the stroma. Increased expression of
inflammatory markers such as HLA-DR is also seen. It would
appear that the preservative benzalkonium chloride, present
in many topical therapies, is responsible for most of the
induced chronic inflammation. Such ‘activation’ of the
conjunctiva is associated with significantly reduced
success rates for filtration surgery. There is consequently a
growing call for more widespread availability of
unpreserved formulations of topical glaucoma medication .

Preoperative Conjunctival Health
and Trabeculectomy Outcome
• Other causes of an activated, profibrotic cellular
state are previous ocular surgery, certain
secondary causes of glaucoma, black race, and
possibly youth. Thorough preoperative evaluation
of risk factors, together with conjunctival
examination, will help to determine the level of risk
for trabeculectomy failure, allow preoperative
treatment to minimize this risk, and determine
whether antimetabolites should be employed

Introduction
• Trabeculectomy is more likely to be successful
when the blood–aqueous barrier is pristine and
conjunctiva untouched, as in the primary
glaucomas. However, when anterior segment
anatomy is altered, conjunctiva violated, or the
blood–aqueous barrier disrupted, trabeculectomy is
less effective in the long term, but fortunately
offers short-term IOP control in emergency
situations. The secondary glaucomas typically fare
better with glaucoma drainage devices. Eyes that
have severe scarring of the conjunctiva are not
good candidates for filtration surgery

Introduction
• Subconjunctival fibrosis leading to bleb failure is the most
common cause of trabeculectomy failure. Known risk
factors for failure of filtration after trabeculectomy include
previous ocular surgery, such as failed initial
trabeculectomy, cataract surgery, or any conjunctival
incisional procedure; secondary glaucoma due to
neovascular, traumatic, or uveitic conditions; race of
African origin; long-term therapy with multiple topical
antiglaucoma drugs; and young age. Risk factors for failure
appear to result in priming the conjunctival cell profile to
react more vigorously to surgical insult, leading to
enhanced post-trabeculectomy fibrosis. With the growing
emphasis on modulation of the wound healing response to
achieve greater success rates of filtration surgery, there is
increasing recognition of the importance of risk factors for
failure

MEDICAL VS SURGICAL
• Currently, the majority of glaucoma specialists
advocate trabeculectomy only after medical
therapy has failed, this being in spite of the
evidence that trabeculectomy is more efficacious
in lowering intraocular pressure (IOP) in
comparison with medical therapy .

MEDICAL VS SURGICAL
• Trabeculectomy and tube shunt both appear to be
attractive surgical alternatives in a select group of
glaucoma patients. Patients must understand that
although the risk of failure is low in their particular
case, the operation may not be successful and that
some complication may occur that could make
their ocular condition worse. Today, as in decades
past, the surgeon and patient together must decide
individually which approach is best, but data do
exist to help with the decision-making process.

Trabeculectomy
• Trabeculectomy remains a valuable procedure for pressure
reduction in uncontrolled glaucoma. This procedure
consistently lowers IOP into a range that usually prevents
further blindness. The physician should better understand
basic concepts of filtration surgery and how to best achieve
favorable results. The problems with trabeculectomy involve
the unpredictable art of wound healing. If excessive scarring
occurs, the filter will fail. If inadequate scarring occurs, then
the eye will become hypotonous. A fine line exists between
excessive scarring and inadequate scarring. This frustration,
along with the other inherent flaws with trabeculectomy, will
continue to be the driving force behind the desire for improved
surgical procedures for our glaucoma patients.

Introduction
• Lowering intraocular pressure is currently the only
evidence-based modifiable risk factor for treating
glaucoma and no other operation consistently lowers
pressure as well as trabeculectomy. In eyes with
primary open-angle glaucoma devoid of prior incisional
surgery, trabeculectomy remains the gold standard for
intraocular pressure (IOP) reduction. Successful
trabeculectomy forms an alternative drainage system
for the eye that significantly lowers IOP by diverting
aqueous humor into the subconjunctival space,
establishing a filtering bleb under the upper lid. This
diverts aqueous humor away from the patient’s
diseased collector system, causing Schlemm’s canal to
become smaller

Trabeculectomy
• Trabeculectomy is more likely to be successful when the blood–aqueous
barrier is pristine and conjunctiva untouched, as in the primary
glaucomas. However, when anterior segment anatomy is altered,
conjunctiva violated, or the blood–aqueous barrier disrupted,
trabeculectomy is less effective in the long term, but fortunately offers
short-term IOP control in emergency situations. The secondary
glaucomas typically fare better with glaucoma drainage devices. Eyes
that have severe scarring of the conjunctiva are not good candidates for
filtration surgery.
• An IOP in the low teens after a filter2 typically stabilizes glaucoma and
allays the fear of blindness for all involved in the care of the patient.3
This significantly enhances quality of life for not only the patient and
their immediate family, but for all caregivers. The overall socioeconomic
burden of glaucoma management is vastly improved after successful
filtration surgery because the patient is less dependent on drops,
compliance is less of an issue, patient well-being and attitude vastly
improve, and clinic follow-up and diagnostic tests are reduced.

Trabeculectomy
• The evolution of glaucoma filtering surgery
involves wound modulation with antimetabolites
and collagen matrix, placement and timing of
antimetabolite application, timing of postoperative
suture lysis, improvements in wound architecture,
flow regulators, watertight conjunctival closure,
and postoperative management.8,9 However, in
spite of the surgeon’s best efforts, wound
modulation is not always successful; excessive
flow may occur, resulting in hypotony or exuberant
scarring may occur leading to filtration failure

Trabeculectomy
• In addition, an undesirable bleb may develop
causing tearing, burning, leaking, and stinging with
foreign body sensation . In spite of these problems,
glaucoma surgeons continually turn to
trabeculectomy to significantly lower IOP,
especially in patients with advanced disc damage
or patients intolerant or poorly adherent to medical
therapy

Trabeculectomy
• Glaucoma surgery is high risk and high
maintenance, requiring intensive postoperative
management. Even after successful
trabeculectomy surgery, there may be a slight
reduction in vision due to a refractive change,
astigmatism, reduced axial length, cataract,
hypotony, or loss of visual field due to split fixation.
Many of these problems are transient and relatively
minor when compared to the benefit of vision
preservation.

Filtration failure
• Severe injection of
conjunctiva post filter with
imminent bleb failure. This
bleb will fail due to
excessive fibrosis
associated with high
vascularity. A host of
fibroblastic factors are
brought in by these vessels,
leading to scarring of the
bleb. Any number of
circumstances can produce
this scenario, especially a
sick blood–aqueous barrier.

Filtration failure
• Filter failure with no bleb.
This filter failed 15 years
after surgery. It controlled
IOP for 10 years and then
started failing. Topical
medications were
restarted and now there
is no bleb present. This is
the typical scenario of a
failing filter. The initial
procedure was a limbus-
based filter in a 25-year-
old African-American
male.

Symptomatic filtering bleb
• This bleb has induced
considerable astigmatism
secondary to extension onto
the cornea. This results from a
‘ring of scar tissue’ (blue
arrows), that forms secondary
to exuberant wound healing at
the posterior boundary of this
limbus-based trabeculectomy
near the conjunctival incision.
This scarring prevents any
posterior flow of aqueous
humor leading to an anterior
dissection down onto the
cornea. Vision is reduced and
a symptomatic bleb is present.

• This bleb is symptomatic
and the IOP is low due to
overfiltration. This is an
extreme example of a
bleb having a ‘mind of its
own.’ This symptomatic
bleb formed over 10 years
and finally required
removal and repair with a
conjunctival patch graft.
This bleb caused chronic
irritation, pain, and
tearing.

• Repair of eye in Fig. 77-
3B with an autologous
conjunctival patch
graft. This normalized
the IOP and reduced
pain, tearing, and
foreign body sensation.
This eye is now 3
months post repair.

TRABECULECTOMY
• The Collaborative Initial Glaucoma Treatment
Study (CIGTS) compared trabeculectomy to
medications as initial therapy for primary open-
angle glaucoma. The CIGTS supports early surgical
intervention for patients who presented with more
advanced disease compared to medical therapy.
The Tube versus Trabeculectomy (TVT) study has
demonstrated that both of these surgical
procedures were associated with similar IOP
reduction

TRABECULECTOMY
• The outcome of filtration surgery is highly
dependent on type of glaucoma, severity of
disease, ethnicity, ocular surface disease,
pharmacological wound modulation, surgical
technique, and skill level. Now we will focuses on
the factors most important to a successful filtering
procedure.

TRABECULECTOMY
• Patients with advanced glaucoma damage, defined as
significant disc damage with rim loss or worrisome
visual field loss, require a lower IOP, often in the low
teens or possibly single digits in severe cases. These
patients are likely better candidates for penetrating
surgery such as trabeculectomy. Additionally,
socioeconomic factors figure into the decision tree for
glaucoma surgery. Patients who are intolerant to
glaucoma medications, unable to administer them,
poorly adherent to medications, forgetful, or unable to
afford medications may fare better with a filter as they
will probably be less dependent on topical therapy.
Another benefit of filtration surgery is reduction in the
magnitude of IOP elevation associated with postural
change

Trabeculectomy
• Trabeculectomy still remains the most reliable
procedure to lower IOP in the vast majority of
patients with uncontrolled POAG devoid of prior
incisional ocular surgery. The typical indication for
surgical intervention is progressive or anticipated
glaucomatous damage that is likely to lead to
functional impairment during the patient’s lifetime

THE ANTIMETABOLITE DECISION: NONE,
5-FLUOROURACIL, OR MITOMYCIN C
• excessive fibrosis leading to bleb failure and elevated IOP is
consistently the most aggravating problem post filtration.
The most common agents to inhibit fibrosis are topical
corticosteroids27 and antimetabolites.28 The
antimetabolites 5-fluorouracil (5-FU) and mitomycin C (MMC)
are used commonly and inhibit fibrosis29 resulting in lower
postoperative IOP after trabeculectomy. In a prospective
randomized trial comparing trabeculectomy with adjunctive
intraoperative 5-FU to placebo, 5-FU increased the success
rate with a single intraoperative application.30 In patients
at relatively low risk for filtration failure, intraoperative
MMC 0.2/mg cc for 2 minutes had similar efficacy as
intraoperative 5-FU 50 mg/mL for 5 minutes.31,32 A large
retrospective study from the Wilmer Institute found
intraoperative MMC more effective than intraoperative 5-FU

Factors Associated with
Filtration Failure
• 1. Secondary glaucomas
• Neovascular glaucoma
• Aphakia
• Uveitis
• Traumatic
• 2. African race
• 3. Prior failed filtration
• 4. Young age

Filtration Failure
• 5. Diabetes
• 6. Superior rectus bridle suture
• 7. The need for a very low postoperative IOP
• 8. Combined cataract and glaucoma surgery (use
MMC)
• 9. Conjunctival scarring (example from scleral
buckle surgery)
• 10. Pseudophakia

Filtration Failure
• 11. Any situation that changes the blood–aqueous
barrier
• 12. Altered anterior segment anatomy (example
penetrating keratoplasty)
• 13. Ocular surface disease such as ocular rosacea
• 14. Surgeon experience
• 15. Postoperative inflammation
• 16. Subconjunctival anesthetic
• 17. High IOP during the first 2 weeks post-filtration
surgery

BLEB CHARACTERISTICS AND
MORPHOLOGY
• The heart of glaucoma surgery is the maturation of the
bleb, especially during the first 3 postoperative months
The most desirable blebs are shallow, widespread, pale
but not avascular, limited to under the upper lid, and
rapidly develop epithelial microcysts . A plethora of
microcysts seen during slit-lamp exam almost always
correlates well with a favorable outcome. These
microcysts are located at the level of the epithelium
and contain proteinacous debris. Microcysts represent
clinical and laboratory evidence for transconjunctival
movement of aqueous post filtration surgery. Many
blebs start out this way, but over a 3-month period
become localized . These blebs become cystic,
localized, elevated, and ultimately pale and avascular

BLEB CHARACTERISTICS AND
MORPHOLOGY
• The wall of the bleb may thicken or become very
thin (both of which are undesirable). Opinions vary
greatly as to how to best achieve the ultimate bleb.
Filtering blebs47 show decreases in overall
epithelial thickness, goblet cell density, and
vascularity. There is also a loss of localized
stromal vascularity. These characteristics clearly
explain the increased risk of blebitis and
endophthalmitis.

Bleb Grading Scale
• Mitomycin C has a dramatic effect on bleb evolution. The mean
time to bleb avascularity post MMC-augmented trabeculectomy
is approximately 100 days when the MMC is applied directly
over the filtering site. This avascularity is the key factor leading
to bleb leaks seen in 26% of eyes at 2 years. Many physicians
use a bleb grading scale to try to better understand bleb
characteristics and follow bleb morphology. In the Indiana Bleb
Grading Scale,50 the height, extent, vascularity, and Seidel
leakage of the bleb are routinely graded. This scale is helpful in
understanding the clinical appearance of the bleb and
understanding postoperative bleb evolution and function. For
example, the bleb in Figure 77-1B has the characteristics
H2E2V2S0. This implies moderate bleb height (H), 2 to 4 clock
hours of elevation (E), mild vascularity (V), and no Seidel (S).
The bleb in Figure 77-2A is H1E2V4S0, implying a shallow bleb,
with an extent of 2 to 4 clock hours but highly vascular with no
leak

The optimal bleb post fornix-
based trabeculectomy
• Bleb appearance. This slit-lamp
photograph illustrates the
characteristics of the perfect bleb.
The bleb is totally asymptomatic,
delivering an excellent IOP of 12
mmHg without topical medications, 5
years later. The desirable features
include a diffuse, shallow bleb. The
bleb is largely pale but yet slightly
vascular, definitely not avascular.
There are many microcysts present.
The bleb is not too thin in any area.
The patient has no bleb-related
symptoms: no tearing, no burning,
and no foreign body sensation. The
bleb does not induce astigmatism or
any type of dysesthesia.

The optimal bleb post limbus-
• Bleb appearance. The blue
arrows point to the
conjunctival incision. Often,
this area will scar and the
incision is pulled towards the
limbus. This did not occur in
this case. This bleb has the
desirable characteristics of
good IOP control, shallow and
diffuse, some vessels on the
surface, with an overall pale
appearance but not avascular.
This bleb is slightly more
elevated over the filtration
site, which is more common
with a limbus-based filter.

LIMBAL ANATOMY
• The limbal blue zone, or surgical limbus, is roughly 1.5 mm
and is the most important anatomic landmark for glaucoma
surgery. The anterior extent of the blue zone is the
corneolimbal junction and the posterior extent is the
junction with the sclera, the sclerolimbal junction. A
perpendicular incision made at the posterior extent of the
blue zone, the sclerolimbal junction, would enter the
anterior chamber at the anterior meshwork/Schwalbe’s line
area as shown in Figure 77-5 B and C. Therefore, the scleral
spur is located posterior to the blue surgical zone. Figure
77-5 demonstrates how far posterior the scleral spur may
be, for this anatomy varies widely and must be determined
by the surgeon intraoperatively. Knowledge of these angle
structures is key when performing a trabeculectomy as well
as when performing an Ex-Press shunt

Limbal anatomy
• (A) Limbal anatomy is highly
variable. The limbal zone is a
1.5 mm transition area
between sclera and cornea.
The posterior extent of this
blue zone is noted by the blue
arrow and the anterior extent
by the green arrow. Obviously,
the scleral spur can not be
seen but, in general, a
perpendicular incision through
sclera at the blue arrow would
be near the anterior trabecular
meshwork/Schwalbe’s line.
The black arrow is the actual
position of the spur as seen
after the dissection in the
figure. (

Limbal anatomy
• The black arrow denotes the
scleral spur, and Schlemm’s canal
is located directly anterior to the
spur. Schwalbe’s line is seen as
the peripheral extent of the
cornea (blue arrow). The most
common error during filtration
surgery is flap location with
failure to extend the flap far
enough posteriorly or anteriorly.
This flap appears to have
adequate posterior extension, but
note the posterior extent of
scleral spur. The problem with a
short flap would be failure to
adequately cover the
sclerostomy.

Limbal anatomy
• Correlate the anatomy
beneath the scleral flap
in Fig. 77-5B with the
gonioscopic view. The
scleral spur is the black
arrow and Schwalbe’s
line the blue arrow

FORNIX-BASED CONJUNCTIVAL
INCISION
• Many investigators believe a fornix-based
conjunctival flap is better than a limbus-based one.
Kano and Kuwayama evaluated the characteristics
of filtering blebs after a fornix-based approach and
found most blebs were pale, diffuse, and leak-free.
The majority had diffuse blebs at 72%, with 60%
vascular. There were no late-onset bleb leaks and
cystic blebs were uncommon

LIMBUS-BASED CONJUNCTIVAL
FLAPS
• In pediatric and young adult filters with high-dose
antimetabolites, the risk of a cystic bleb developing
is much greater with a limbus-based conjunctival
flap (90%) than a fornix-based flap (29%). In
addition, late hypotony and blebitis were more
common with a limbus-based approach. Wells et al.
felt strongly that a limbus-based approach was
much more likely to lead to a cystic bleb in young
patients.54 The authors have certainly seen a
similar outcome in adults

LIMBUS-BASED CONJUNCTIVAL
FLAPS
• hypotony was more common with fornix-based filters.
The same study found limbus-based filters to be higher
and more avascular and slightly more prone to blebitis.
Morita and colleagues used in vivo confocal
microscopy and ultrasound to study blebs. They found
limbus-based filters had a higher height of the fluid-
filled space, along with a thinner wall of the bleb, lower
density of subepithelial connective tissue and a greater
avascularity of subepithelial tissue than fornix-based
filters. These characteristics of a limbus-based filter
may be associated with long-term leaks and related
problems.

FORNIX-BASED
TRABECULECTOMY
• Fornix-based filters are experiencing a
renaissance. Many investigators feel that bleb
characteristics are more desirable with a fornix-
based approach, with less symptomatic blebs that
are free from long-term leaks In addition, a fornix-
based conjunctival flap is preferable for eyes that
have conjunctival scarring. Patients with
enophthalmos or small palpebral fissures are
clearly candidates for a fornix-based approach

FORNIX- VERSUS LIMBUS-BASED
CONJUNCTIVAL FLAPS
• (A) The conjunctival
incision for a limbus-
based approach is made
approximately 10 mm
from the limbus. At this
location, it is common
to detect some
underlying Tenon’s
capsule that facilitates
the final closure

CONJUNCTIVAL FLAPS
• (B) This eye is 4 months
post filter, limbus-based
approach, and note the
incision is well back
from the limbus, the eye
is quiet, and a diffuse
bleb formed

CONJUNCTIVAL FLAPS
• (C) In this case, the
incision noted by the blue
arrows is migrating
towards the limbus, the
vessels are engorged and
injected, and this bleb will
probably turn cystic, pale
and avascular. This wall
of scar tissue will be a
barrier to posterior flow
of aqueous, creating a
more forward, undesirable
cystic bleb

CONJUNCTIVAL FLAPS
• (D) When the incision
migrates forward or is
associated with
excessive scarring, the
bleb turns pale and
avascular and the
suture line is seen at
the posterior aspect of
the bleb. Because the
bleb area is limited, the
IOP control is often
marginal.

CONJUNCTIVAL FLAPS
• (E) The conjunctival
incision for a fornix-
based approach is at
the limbus, for the
nomenclature for fornix-
or limbus-based is
where the flap hinges,
not where it is incised

CONJUNCTIVAL FLAPS
• (F) In the majority of cases,
the bleb develops as seen in
. However, in this case, a
cystic bleb with thin
conjunctiva developed in
spite of the approach, and
the antimetabolite was
placed posterior to the
filtration site. Even under
the best of circumstances,
either with a fornix- or
limbus-based approach, an
undesirable bleb may form

A diffuse shallow desirable bleb created
with a fornix-based approach.

Anatomy of a bleb
• Anatomy of a bleb as
seen with high-
resolution ultrasound
from iScience
corporation, Menlo
Park, CA. The wall of
the bleb appears thick,
but it functions quite
well, with an IOP of 12
mmHg.

Anatomy of a bleb
• A pale, avascular cystic
bleb following a limbus-
in the fellow eye of the
patient featured in
Figures 77-6G and 77-
6H. The wall is thin and
worrisome from an
infectious viewpoint. In
addition, the bleb was
symptomatic

Anatomy of a bleb
• A high-resolution
ultrasound image of a
pale avascular bleb,
allowing one to better
appreciate bleb
anatomy and function.

Mitomycin C
• Mitomycin C applied intraoperatively was the first
antifibrotic agent used to increase the success of
fil tration surgery Concentrations of 0.2 to 0.5
mg/ ml for 2 to 5 minutes have been used.. MMC is
more potent than 5-FU7 . Higher concentrations
and longer duration are associated
withgreatereffectbutwith a greater likelihood of
complications, like a very thin avascular bleb and
post-operative hypotony.8,9 Most surgeons
currently use a concentration of 0.2 or 0.4 mg/ml
for 2 to 3 minutes.

Method of Application of MMC
• MMC-soaked sponge (Mersel or polyvinyl) is placed on the
intact scleral surface before dissecting the scleral flap. This
technique may reduce the penetration of the drug to the
ciliary body, where it can cause prolonged postoperative
hypotony and prevents drug entry into the anterior chamber
where it may cause endothelial toxicity. The conjunctiva
and tenon’s capsule is draped over the sponge, making sure
that the cut edge does not come in contact with it. The
surgical site is irrigated with 15 to 30 ml of balanced salt
solution, which is collected on gauze pads. The remainder
of the trabeculectomy is performed as described previously,
with special attention given to creating a tight closure of
the scleral flap, in order to maintain a formed anterior
chamber, and performing a watertight conjunctival closure
using a tapered needle.

Mitomycin MMC soaked sponges are
used for intraoperative application

FORNIX-BASED
TRABECULECTOMY
• Fornix-based filters are experiencing a
renaissance. Many investigators feel that bleb
characteristics are more desirable with a fornix-
based approach, with less symptomatic blebs that
are free from long-term leaks. In addition, a fornix-
based conjunctival flap is preferable for eyes that
have conjunctival scarring. Patients with
enophthalmos or small palpebral fissures are
clearly candidates for a fornix-based approach

TRACTION SUTURE, MANAGEMENT OF
TENON’S CAPSULE, AND CREATION OF A
FORNIX-BASED INCISION
• A corneal traction suture is preferable to a superior
rectus bridle suture for several reasons. The bridle
suture creates undesirable holes in the conjunctiva
and has a potential to perforate the globe during
passage of the needle. The globe is rotated
inferiorly (as seen in Fig. 77-7A) by pinching the
drape around the suture with a hemostat

Corneal traction suture.
• (A) An 8-0 polyglactin
superior corneal traction
suture is placed two-
thirds thickness into
peripheral clear cornea
and the globe is rotated
down to expose the
superior conjunctiva.
Failure to adequately
expose the area of regard
makes surgery much
more difficult.

• Tent the limbal conjunctiva up about 1 mm from the
limbus and incise the conjunctiva, creating a
peritomy. The conjunctiva and Tenon’s capsule is
incised at the limbus for 5–7 mm using Westcott
scissors (Fig. 77-7B). Occasionally, a radial
conjunctival relaxing incision is required to gain
adequate exposure. It is imperative to hug the
limbus while pressing the scissors against the
conjunctiva to sever it at its insertion to the limbus.
The authors prefer to visualize the insertion of
Tenon’s capsule while elevating the conjunctiva, so
that both tissues can be incised at the same time

conjunctival incision
• (B) Fornix-based
conjunctival incision.
Incise the conjunctiva
with sharp Westcott
scissors. It may be
necessary to create a
small radial cut to start
the dissection.

• Use blunt-tipped Westcott scissors to fashion a
subconjunctival pocket by dissecting the
conjunctiva and Tenon’s capsule off the episclera
(Fig. 77-7C). Avoid the superior rectus during the
dissection. The conjunctiva must only be
manipulated with atraumatic forceps. If
buttonholes occur during dissection, the defect can
be repaired by incorporating Tenon’s tissue during
the conjunctival closure. During complicated
conjunctival closure, the authors prefer to use a
tapered 10-0 microvascular needle

• (C) Attachment of Tenon’s capsule
near the limbus. The conjunctiva and
Tenon’s capsule fuse as the tissues
approach the limbus. Approximately
1.5 mm from the limbus, Tenon’s
capsule fuses with the underlying
episclera as seen at the black arrow.
Sever these adhesions with the blunt
Westcott scissors resting on the
sclera to avoid tearing the tissue.
Avoid a buttonhole of the conjunctiva
at this area (black arrow). Once
Tenon’s is separated from the sclera,
dissect it as a single layer with the
conjunctiva. Tenon’s is also attached
to the sclera in the area adjacent to
the insertion of the superior rectus
muscle. The insertion of the
conjunctiva onto the cornea is
variable; occasionally, the insertion is
more anterior than anticipated

CREATION OF A FORNIX-BASED
INCISION
• It is essential to incorporate Tenon’s capsule when
closing the conjunctiva (Fig. 77-7D). In this era of
antimetabolites, just enough Tenon’s capsule is
removed to visualize the underlying scleral flap
sutures. Leaving a thin layer of Tenon’s capsule
reduces long-term bleb breakdown, hypotony, and
endophthalmitis, but an excess of Tenon’s capsule
may lead to fibrosis and filtration failure

• (D) Edge of Tenon’s and
conjunctiva. The anterior edge
of Tenon’s is located by the
blue arrow. If excessive, which
is uncommon, it may be
slightly trimmed. The key is to
free the Tenon’s fascia from
the episclera and then grasp
the edges of both conjunctiva
and Tenon’s when separating
the two layers from the rest of
the underlying sclera.
Protecting the edge of Tenon’s
is important, for it serves as a
gasket to prevent leaks at the
limbus during the
postoperative period.

• (E) Blunt dissection of
conjunctiva. Dissect
Tenon’s and conjunctiva
from the episclera with
blunt Westcott scissors. It
is important to
continually visualize the
tips of the scissors during
the dissection to prevent
perforation. In addition,
the dissection is aimed
towards the quadrants on
either side of the
insertion of the superior
rectus muscle. (

APPLICATION OF
ANTIMETABOLITE
• The decisions regarding antimetabolite use must
be made prior to surgery. Typically, the greater the
number and magnitude of risk factors for filtration
failure, the more potent the antimetabolite. The
first decision is whether the case carries a low,
medium, or high risk for failure. For low risk of
failure, some surgeons prefer no antimetabolite.
Postoperatively, if the bleb is injected, a series of 5
mg 5-fluorouracil (5-FU) injections is administered
into the inferior cul-de-sac or adjacent to the bleb.

Application of MMC soaked
sponges
• (F) The general theme
of MMC application is to
cover a broad area with
several sponges, all
placed posterior to the
intended area of
filtration. The
concentration and time
of application vary,
depending on risk
factors.

sponges
• (G) Notice how far
posterior the sponge is
located; it is placed,
well away from the
intended area of
filtration. Do not place
the sponge directly over
the scleral flap, for this
may lead to
scleromalacia of the
flap.

sponges
• (H) The authors typically use
three MMC pledgets, soaked in
MMC, 0.2 mg/mL, placed for 2–
5 minutes, depending on the
case. After the specified time,
the pledgets are removed,
sponge count performed, and
the area is vigorously irrigated
with balanced salt solution
(BSS). With posterior sponge
placement, the sponge is out
of sight and easily forgotten. A
well-trained and vigilant
surgical assistant keeps track
of the sponge count.

APPLICATION OF
ANTIMETABOLITE
• For medium-risk cases, either an intraoperative
sponge application of 0.1 mL of 5-FU (50 mg/mL) for
5 minutes or low-dose mitomycin C (MMC) (0.2
mg/mL for 2–5 minutes) is indicated, and
postoperative injections of 5-FU titrated if
necessary. If only one risk factor is present, 2–3
minutes of MMC application is appropriate; for
multiple risk factors, 3–5 minutes.

APPLICATION OF
ANTIMETABOLITE
• For high-risk eyes, some surgeons use MMC (0.4
mg/mL) for a period of 2–5 minutes. However, if
these potent concentrations are used in low- or
medium-risk eyes, long-term hypotony and bleb
breakdown are more likely. Prior to scleral flap
dissection, a rectangular segment of Merocel
instrument wipe or Weck-cell sponge soaked with
either 5-FU 50 mg/mL or MMC is placed posterior to
the intended site of filtration.

APPLICATION OF
ANTIMETABOLITE
• Avoid placing it directly over the area of intended
filtration for this leads to pale avascular blebs.
Immediately after the pledget has been placed, any
pools of antimetabolite present are soaked up
using a Weck-cell sponge, which is discarded. The
size of the pledget varies and is not standardized;
the surgeon uses best judgment depending on risk
factors and anatomy

APPLICATION OF
ANTIMETABOLITE
• The conjunctiva is retracted, the sponge is
removed, and copious irrigation applied to the
contacted area. The use of MMC is nearly
ubiquitous in glaucoma surgery, however glaucoma
specialists are constantly looking for improved
alternatives which may allow for a better and safer
bleb.

APPLICATION OF
ANTIMETABOLITE
• One potential wound-modulating material currently being
investigated is Ologen (Aeon Astron Europe B.V.), a porous
collagen matrix that is thought to modulate wound healing.
Theoretically, the major functions of this collagen matrix
are achieved by physical principles rather than chemical
ones. The proposed mechanism of bleb formation is not by
suppressing or inhibiting fibroblast growth, but rather
guiding fibroblasts to grow randomly inside the matrix.
Modulating fibroblast behavior is thought to produce a more
physiological environment without scar formation, thus
creating a sub-conjunctival space for a bleb and
theoretically preventing hypotony.58–62 The collagen matrix
is thought to eventually biodegrade within 90–180 days.
Although fundamental studies of Ologen demonstrating
efficacy are currently underway, there are currently no
studies demonstrating the long-term success of Ologen.

OUTLINE SCLERAL FLAP
• The flap is first outlined prior to its dissection. A
variety of instruments may be used to dissect the
partial-thickness scleral flap, such as a No. 67 Beaver
blade, razor blade, or Greishauber blade. The choice of
instrument is by surgeon’s preference and may vary
slightly from case to case. Initially, the borders of the
flap are outlined to two-thirds of the scleral thickness.
If the flap is too thin, it has a tendency to shred.
Extreme care should be taken with myopic eyes as the
sclera is typically thinner than average. Special
precautions are necessary when flaps are fashioned in
eyes that have undergone previous limbal surgery,
especially prior filtration or cataract surgery.

Incise and outline sclera
• (I) Incise the sclera with a
super sharp blade
approximately 5 mm from
the limbus for a chord
length of 3 mm. The depth
should be two-thirds
thickness. Note the
length of the conjunctiva
incision at the limbus,
which can vary from 5
mm to 7 mm depending
on the size of the eye and
exposure.

• (J) The most common
error relates to the depth
of the incision. The
tendency is to go one-
quarter or one-half depth
for fear of penetrating the
choroid. If the initial
incision is not deep
enough, the flap, as it is
dissected, is more likely
to shred during
manipulation or
buttonhole during flap
closure.

• (K) Proper depth is determined
by retracting the sides of the
incision and inspecting the
depth. A good sign is a light-
gray color as seen in the
depths of the incision as the
floor of the sclera is reached.
If too deep, the choroid will
appear, clearly a red flag to
cease dissection. When there
is excessive bleeding in the
surgical field and inadequate
hemostasis, one can easily
misjudge flap thickness and
run into problems.

• (L) The shape of the scleral
flap is the surgeon’s
preference. A trapezoidal flap
is useful with a fornix-based
conjunctival incision because
the posterior edge of the flap
is closer to the limbus where
there is room to work. The
apex of a triangular-shaped
flap would be located under
the conjunctiva, making it
difficult to suture. The lateral
sides of the flap should extend
into clear cornea at the limbal
transition zone. The depth of
the incision is inspected
(black arrow) to make sure of
adequate exposure.

• (M) The flap is outlined. The
sides and base are 5 mm
and the top is 3 mm. When
first learning how to fashion
a scleral flap, it is
preferable to err on a larger
size such as in this
example, for a larger-sized
flap is more forgiving during
a recovery maneuver such
as for inadequate depth. In
addition, if the posterior
margin of the flap is too
anterior, there is not
adequate coverage of the
sclerectomy site.

Fashion scleral flap
• (N) There are several
instruments available for
flap dissection. A
supersharp blade works
well to initiate the
appropriate depth of the
incision at two-thirds
thickness. It may take a
millimeter to find the
correct plane: again,
another reason to learn
with generous flaps as
they are more forgiving.

• (O) Once the correct plane is
achieved, use a curved
Grieshaber blade to advance
the flap in the same plane
towards the limbus. As the
scleral spur, or corneoscleral
sulcus, is approached, the
curvature of the globe
changes and a more anterior
plane must be followed. If a
more anterior plane is not
obtained, the dissection will
go through the spur and
trabecula and into the anterior
chamber or, even worse, into
the choroid.

• (P) The black arrow denotes
the scleral spur and the green
arrow Schwalbe’s line. Carry
the dissection well into clear
cornea to ensure adequate
removal of trabecular and
associated tissue anterior to
the scleral spur. Any removal
of sclera posterior to the black
arrow will potentially create a
cyclodialysis cleft, as in the
old Watson-type
trabeculectomy. In addition,
removal of tissue posterior to
the spur results in
considerable bleeding.

scleral flap
• (P1) A crescent blade
dissection is another
method to create a
scleral flap. Physicians
familiar with creating a
scleral tunnel for cataract
surgery are familiar with
this technique. After
making the tunnel, simply
use Vannas scissors to
create the sides of the
flap.

scleral flap
• (P2) A minispoon blade is
another useful instrument
for creating a flap. Once the
flap is initiated, this curved
minispoon blade allows a
very fine dissection of the
flap. Use very purposeful
movements, hugging the
scleral bed and dissecting
while there is tension on the
flap as it is retracted.
Careful tension on the distal
end of the flap in anterior
direction will aid in an even
and consistent dissection.

FLAP SIZE.
• In general, the shape of the flap does not matter as
long as it is constructed properly and is able to cover
the corneoscleral block removal site adequately. Flap
size will vary according to the adjacent anatomy. Most
trapezoidal flaps range between 4–5 mm at their base
and sides with the posterior limit at 2–3 mm. Triangular
flaps may be slightly smaller. Thin flaps tear or avulse
from the bed and may tear during suture closure.
Dissection into clear cornea assures adequate room for
removal of the corneoscleral block. Thick flaps
probably are not detrimental because postoperatively
the bulk of flow occurs through the wound margins of
the scleral flap

FLAP LOCATION
• The dissection is kept as close to the 12 o’clock
position as possible because excessive medial or
lateral flap placement leads to symptomatic
filtering blebs and potentially would interfere with
future tube placement. Prior to glaucoma drainage
implants, some physicians preferred to place the
filter on either side of the 12 o’clock position. If the
first filter failed, a second could be made in the
adjacent quadrant. This, however, would make it
more difficult to insert a drainage implant, the
placement and usage of which is increasing over a
second filter.

FLAP DISSECTION
• Flap dissection must be initiated at one of the
posterior corners of the flap. Once an edge has
been dissected, the freehand dissection is carried
forward uniformly into clear cornea anterior to the
trabecular meshwork. This assures enough room
for block removal without removal of scleral spur,
which may lead to an inadvertent cyclodialysis and
considerable bleeding.

FLAP DISSECTION
• In eyes with previous limbal cataract surgery, a scleral
tunnel technique is beneficial. A scleral tunnel incision
minimizes the traction on the flap and is less likely to
cause the flap to break at the old incision line. The
scleral tunnel is constructed by creating a two-thirds-
thickness incision of sclera tangentially, 3–4 mm
posterior to the limbus, for a width of 3–4 mm. Use a
crescent blade to tunnel into clear cornea in the same
fashion as for cataract surgery. Slide the blade from
side to side until the flap is about 4 mm in width. The
flap is finished by using Vannas scissors to incise the
lateral edges, thus creating a three-sided flap

PREPLACED SCLERAL FLAP
SUTURES
• Flap sutures are much easier to place before the
eye is hypotonous. The flap sutures should not be
full thickness, as this may cause a leak.

Preplaced scleral flap sutures.
• Q) The less time the eye is
open to atmospheric
pressure, the less the
likelihood of a
suprachoroidal hemorrhage
or related event. Therefore,
preplaced flap sutures are
extremely useful for rapidly
closing the wound. Observe
that the suture exits the
side of the flap, not through
the bottom of the flap. This
prevents a buttonhole from
forming in a thin flap. A 10-0
nylon suture is effective for
flap closure.

PARACENTESIS
• The eye must be
relatively firm to create
a paracentesis tract.
The uses are multiple

Paracentesis.
• (R) Paracentesis is one of
the most important steps
during filtration surgery
(see Box 77-5). Use a
supersharp blade to enter
completely through the
cornea and into the
anterior chamber.
Incomplete penetration
may lead to a Descemet’s
detachment. (S–V)
Removal of corneal–
trabecular–scleral block.

REMOVAL OF CORNEOSCLERAL
BLOCK
• Rotate the scleral flap over the cornea and use a 15° supersharp
blade to enter the anterior chamber at the anterior extent of the
scleral bed. Insert the punch through the slit into the anterior
chamber and engage the lip of the scleral bed. Remove a few
sections of tissue to create an adequate block removal. Light
wet-field cautery is applied to the cut ends of Schlemm’s canal,
which significantly reduces the chance of a postoperative
hyphema. The size of the corneoscleral block in relation to the
dimensions of the scleral bed determines the amount of flow
through the filter. A very large corneoscleral block leaves a small
scleral ledge, which may result in overfiltration and hypotony.63
If the corneoscleral block is too small, the ledge is too large and
it is difficult to achieve flow through the flap, especially if it is
secured tightly. Excessive posterior block removal into the ciliary
body may cause an inadvertent cyclodialysis cleft and bleeding.

REMOVAL OF CORNEOSCLERAL
BLOCK
• (S) Use a supersharp
blade to enter the
anterior chamber at the
anterior extent of the
scleral–corneal bed.
Take care to avoid the
iris and visualize the tip
of the blade as it enters
the anterior chamber.
Incise a 2–3 mm area
for insertion of the
punch. (

PUNCH
• (T) A side view of the
punch is shown. The
punch removes
approximately a 1 mm
portion of limbal tissue.

PUNCH
• (U) The obvious reason
to start anteriorly with
the punch is to avoid
cutting into the ciliary
body structures located
posterior to the spur.
These structures bleed
profusely.

PUNCH
• (V) The punch
facilitates a simple
removal of tissue. The
majority of this block
removal is corneal
tissue.
• Figure 77-7 Continued

PERIPHERAL IRIDECTOMY
• Even though iridectomy is rarely needed in modern-day
cataract surgery, it is required for filtration procedures
to relieve pupillary block and prevent obstruction of the
internal filter opening. After removal of the
corneoscleral block, the iris typically obstructs the
opening. If the iris bulges through the block site and is
difficult to reposit, use the DeWecker scissors to make
a small iridotomy in the peripheral iris to relieve the
pupil block. This maneuver usually allows the iris to
recede back into the anterior chamber. The base of the
iris is then grasped using 0.12 forceps and retracted
outside the posterior ledge of the opening in a
tangential fashion.

Peripheral iridectomy
• W) Occasionally, the iris
will prolapse into the
sclerostomy site
immediately after
removing the
corneoscleral block. Do
not try to push it back
into the eye, as this will
damage the iris.

• (X) Instead, make an
iridotomy prior to the
iridectomy. The
iridotomy will relieve
the pressure in the
posterior chamber that
is pushing the iris out of
the eye. It is less
damaging to the iris to
gently reposition it after
the iridotomy with relief
of posterior pressure.

• (Y) The iris is grasped
with a 0.12 forceps and
elevated above the
plane of the
sclerectomy site. A
DeWecker scissors is
convenient to remove a
section of iris, thereby
creating the iridectomy.

• (Z) After removing the
peripheral iris, check
the site for vitreous
with a Weck-cell
sponge. If there is any
remnant of the posterior
layer of the iris, remove
with a Weck-cell
sponge. (

• A small peripheral section of iris is removed using
DeWecker scissors. Aqueous humor pours forth from
the posterior chamber when either the iridotomy or
iridectomy is accomplished. If no fluid is seen, aqueous
misdirection syndrome must be suspected (see
Chapter 84). The iridectomy size should approximate
the size of the block. The patency is checked by direct
observation of lens capsule or red reflex. Posterior
pigment epithelium is removed using a sponge if
needed. In a pseudophakic eye that has a large
posterior capsulotomy, or in aphakic eyes, vitreous
may appear.

• In rare instances, a peripheral iridectomy may be
unnecessary, especially if it might cause vitreous
prolapse. To prevent obstruction of the
sclerostomy, a large basal iridectomy (much larger
than the size of the stoma), is routine for secondary
glaucomas such as neovascular, iridocorneal
endothelialization syndrome, posterior
polymorphous dystrophy, as well as all other
diseases that tend to cause broad peripheral
anterior synechiae (PAS).

SCLERAL FLAP CLOSURE
• After the iridectomy, the eye is quite soft. Immediately,
instead of completely tying each suture in a 3-1-1
configuration, secure each one with the first three
loops of the knot. Insufflate the anterior chamber to
raise the IOP, roughly gauge the flow through the flap,
and finish tying the two posterior sutures. Finish tying
the two anterior sutures at the limbus. This typically
leaves two mid sutures to close with just the correct
amount of tension to have flow through the flap. If the
flap is closed too tightly, no flow occurs and
postoperative IOP is elevated. If the flap is closed too
loosely, overfiltration occurs. Gauging the proper flow
through the filter site is a difficult art, but a critical
step in successful filtration surgery.

• A scant ooze of aqueous through the scleral flap is
a reasonable end point, which is attained by the
adjustment and replacement of sutures as
necessary. This additional operative time may save
hours of postoperative work.
• It is always safer to err on the side of extra flap
sutures. High IOP is easier to treat using scleral
flap suture lysis than a return to surgery to place
additional sutures. If the sutures cannot be seen
intraoperatively, Tenon’s capsule is excised until
they are visible.

Closure of scleral flap with
adequate aqueous egress.
• (AA) All of the preplaced
sutures are temporarily tied,
starting with the posterior set.
The anterior chamber is
insufflated with BSS to
normalize IOP. The flow
through the flap is adjusted by
tightening the sutures trying
to direct flow away from the
limbus. Initially, there were six
sutures in the flap, but one
additional suture on the
temporal side was added due
to excessive flow. This
additional temporal suture will
be the first one to laser
postoperatively if additional
flow is needed.

• As an alternative to laser suture lysis, some
surgeons prefer the placement of releasable
sutures when the scleral flap is closed. These have
a slip knot, the loose end of which is superficially
buried in the cornea, and can be removed using
forceps at the slit lamp at any stage
postoperatively; no thinning of the Tenon’s capsule
is required (see Spotlight 1 on Releasable Sutures
by Mark Sherwood at the end of this chapter).

CLOSURE
• There are a variety of techniques to close the
conjunctiva. Hooded techniques are the simplest, but
the most prone to leaks, especially with antimetabolite
use. A horizontal mattress suture technique described
by Wise64 is the most time consuming and precise, and
yields the best results. A tapered 2850 9-0 nylon needle
that has a tiny cutting tip is used. It is essential to
keep the limbal suture bite longer than the distance
between the corresponding conjunctival suture holes.
When the suture is tightened, the intervening
conjunctiva stretches tightly against the sclera. This is
very effective in the prevention of wound leaks.

CLOSURE
• (AB) Conjunctival
closure. Closure of the
conjunctiva is a
meticulous process in
order to achieve a
watertight closure. This
is imperative for the
success of the filter.

CLOSURE
• a more straightforward and less time-consuming
technique which involves a 10.0 nylon suture and
running and mattress style sutures, the second clip a
running mattress as initially described by Jim Wise MD
(See Videos 77-1 and 77-2). This approach is effective
yet time consuming and may be best for patients with
extremely friable conjunctiva and thin Tenon’s capsule.
As with all techniques, the most dependent variable is
individual surgeon comfort and experience. One should
try as many techniques as possible and attain
proficiency in 2–3 approaches to maximize efficiency
and flexibility. In cases where the conjunctiva is
severely thin, one must entertain the idea of
attempting a different glaucoma procedure and
avoiding a trabeculectomy all together.

INSUFFLATE THE BLEB
• Insufflate the bleb to check for leaks, a critical
step in the evaluation of proper wound closure.

Test the wound.
• (AC) Test the wound.
Inject BSS in the
anterior chamber
through the
paracentesis and
insufflate the bleb to
check for leaks. Place
additional sutures as
needed to guarantee a
watertight closure.

LIMBUS-BASED
TRABECULECTOMY
Filtration surgery requires the physician to master two types
of conjunctival entry incision: fornix-based and limbus-based.

GENERAL PRINCIPLES CONCERNING
REVISION OF A FILTER
• If a filter fails after several years but the surgeon
feels that revising it would be useful, then the skills
necessary for this should be emphasized. The most
common scenario is a functional trabeculectomy
that fails post cataract surgery. The IOP becomes
more difficult to control, medical therapy is
revisited, and ultimately revision is required with
uncontrolled IOP.

Failed fornix-based trabeculectomy
requiring trabeculectomy revision.
• (A) This filter worked well
for several years until
routine uncomplicated clear
corneal cataract surgery.
The prior trabeculectomy
was fornix-based. Either a
repeat fornix-based
approach may be used or,
as in this case, a limbus-
based conjunctival
approach. The superior
conjunctiva is easy to incise
with this approach, for the
tissue in this area was not
violated during the initial
filter.

• If the prior wound is fornix-based, then the
conjunctiva towards the fornix is virgin territory
and may be an easier approach for the wound
revision if the exposure is good. Patients with
severe enophthalmos may require a fornix-based
approach. If the surgeon is not comfortable with
the revision, then consider an aqueous drainage
implant. These devices are becoming more
common in eyes with previous filtration failure, and
many doctors are using these shunts as first-line
therapy in pseudophakic eyes, especially following
the 5-year results of the TVT trial

• demonstrates the necessary steps for a limbus-based
approach to revising a bleb in an eye that has
previously undergone a fornix-based filtration surgery.
Obviously, this approach is applicable for primary
trabeculectomy and any limbus-based approach. Figure
77-9A also highlights several useful maneuvers in an
eye that has had conjunctival surgery of any type.
• In general, limbus-based surgery requires an
experienced assistant because of the need for
conjunctival flap retraction. If the surgeon does not
have adequate help for the procedure, a fornix-based
approach is recommended

CORNEAL TRACTION SUTURE
• A corneal traction suture is required for adequate
conjunctival exposure of the failed bleb in Figure
77-9A. This is the same maneuver as in the fornix-
based approach. Failure to obtain adequate
exposure remains the most common error in
limbus-based trabeculectomy.

Corneal traction suture.
• (B) Adequate exposure of the
operative site is the key
ingredient during a limbus-
based conjunctival approach.
This is accomplished by
placing an 8-0 Vicryl suture
two-thirds thickness through
the cornea at the 11 to 1
o’clock positions. Avoid
perforating the eye, which may
induce a low IOP. The low IOP
makes it more difficult to
construct a flap. If this occurs,
the puncture site may be
hydrated with balanced salt
solution to close the leak and
increase IOP. (

ROTATE AND INSUFFLATE
• Rotate the globe inferiorly (Fig. 77-9C) and secure the traction
suture to the drape. There are a variety of traction sutures; the
technique demonstrated in this figure is a simple one. Once the
globe is properly positioned, pierce the conjunctiva 10 mm from
the limbus with the 30-gauge needle and insufflate the
conjunctiva with balanced salt solution through the needle as
seen in Figure 77-9D. This will help delineate the tissue planes
and enhance dissection as well as reduce the likelihood of
cutting the superior rectus muscle. In this case, the conjunctiva
lifts off the plaque that covers the prior filtration site. However, it
is very adherent to the underlying fibrous tissue near the limbus
(Fig. 77-9D). Use a Weck-cell sponge to massage the
subconjunctival fluid towards the scarred conjunctiva that
requires elevation (Fig. 77-9E). This hydrodissection was
successful, helping to prevent a buttonhole during limbal
dissection.

Rotate and insufflate.
• (C) The globe is rotated
downward to expose the
superior conjunctiva. A 30-
gauge needle attached to a
syringe with balanced salt
solution is inserted into the
conjunctiva in order to
insufflate the tissue. This
separates the conjunctiva
from surrounding Tenon’s
capsule, making it easier to
initially dissect the
conjunctiva from the
underlying connective
tissue.

Insufflate the conjunctiva.
• (D) Roughly 10 mm posterior to the
limbus, insufflate the conjunctiva
with balanced salt solution. The fluid
forces the conjunctiva to elevate,
separating it from underlying scar
tissue making the dissection easier.
This technique aides in dissection
and alerts the surgeon to areas of
scarring and areas prone to a
buttonhole in the conjunctiva. The
conjunctiva does not elevate at
approximately 3 mm from the limbus,
where it was very adherent to
underlying Tenon’s (black arrow). The
benefit of this posterior incision is
that Tenon’s capsule begins to
thicken. A thick Tenon’s capsule is
vital for a watertight conjunctival
closure. Some surgeons will close the
Tenon’s layer first followed by the
conjunctival layer.

Pressure with a Weck-cell sponge.
• (E) Pressure with a
Weck-cell sponge on the
surface of the bleb
spreads and elevates
the more adherent
conjunctiva from the
underlying scar tissue.
This allowed the
conjunctiva to lift off
the limbal area, making
dissection easier. (F

CONJUNCTIVAL AND TENON’S
CAPSULE INCISION
• Initiate the conjunctival incision by inserting the tip of
the scissors into the conjunctival hole made by a 30-
gauge needle and start dissecting conjunctiva from the
underlying tissue (Fig. 77-9F and 77-9G). Retract the
conjunctiva with blunt forceps (Fig. 77-9H). This
exposes the underlying Tenon’s capsule. Capture the
edge of Tenon’s with blunt forceps directly under the
conjunctival wound edge. Dissect the fibrous coat from
the episclera for the entire length of the wound while
avoiding the rectus muscle. This approach typically
maintains a cuff of Tenon’s capsule at the conjunctival
wound margin, which will be vital for a watertight
closure at the completion of this surgery.

CAPSULE INCISION
• (F) Incise the
conjunctiva. The tip of
the sharp Westcott
scissors is inserted into
the same hole made by
the 30-gauge needle
and the conjunctiva is
incised (white arrow).
The conjunctiva is first
dissected free from the
underlying Tenon’s
capsule.

CAPSULE INCISION
• (G) Extend conjunctival incision.
Note that the line of the incision
is at least 10 mm posterior to the
limbus. The most common error
in limbal-based trabeculectomy is
making the conjunctival incision
too close to the limbus. Scar
tissue will always pull the
incision line towards the limbus
as the eye heals during the first 2
months. Exercise caution during
the dissection, for the superior
rectus muscle is directly below
the incision site. Insufflating the
conjunctiva moves it away from
the underlying muscle and
minimizes the chance of a muscle
laceration.

DISSECT CONJUNCTIVAL FLAP
• Once both planes (conjunctiva and Tenon’s) of the
wound margin are exposed, grasp both with blunt
forceps and dissect them together as one from the
underlying sclera. There are several techniques for
this, but the safest is to visualize the scissors through
the transparent conjunctiva during the dissection as
shown in Figure 77-9I. The only time the conjunctiva
requires retraction during this dissection is when scar
tissue is encountered that prevents the dissection. Use
cautery sparingly to prevent necrosis and excessive
tissue shrinkage (Fig. 77-9J). If excessive redundant
Tenon’s is encountered during dissection, it may be
cautiously and sparingly thinned and excised. A Weck-
cell sponge is useful to mechanically separate Tenon’s
capsule from the limbal

DISSECT CONJUNCTIVAL FLAP
• A Weck-cell sponge is useful to mechanically separate
Tenon’s capsule from the limbal junction. Older patients
who have thinner Tenon’s capsules require minimal
manipulation to this layer, whereas younger patients who
have thicker Tenon’s capsules require excision of just
enough tissue to visualize the scleral flap sutures.
Tenonectomy is difficult in younger patients who have
redundant tissue. The best technique to avoid an
inadvertent buttonhole is to visualize the tip of the scissors
at all times through the semitransparent conjunctiva as the
limbus is approached. It is rare today to need a
tenonectomy, for compression with a suture lysis lens will
show the suture during the postoperative period in most
patients. As the limbus is approached, a crescent blade is
useful to separate the strands of Tenon’s from the episclera.

Incise Tenon’s capsule at the
wound margin.
• (H) Once the edge of the
conjunctiva is exposed for its
entire length (white arrow),
the underlying Tenon’s capsule
is apparent (blue arrow).
Switch to blunt Westcott
scissors and open the Tenon’s
capsule, avoiding the
underlying superior rectus
muscle. Separating the layers
facilitates a two-layer closure.
Occasionally, especially in the
elderly, the Tenon’s layer is
very thin and difficult to
dissect intact.

BLUNT DISSECTION
• (I). The blunt Westcott
scissors is an excellent
instrument to safely dissect
conjunctiva and Tenon’s
from the underlying sclera.
At the wound site, grasp the
cut edges of both the
conjunctiva and Tenon’s and
dissect the Tenon’s capsule
off the episclera. During this
process, maintain
visualization of the tip of
the Wescott scissors to
avoid an inadvertent
buttonhole.

Wet-field cautery
• (J) Wet-field cautery and
tissue plane dissection.
Excessive scleral cautery
induces considerable
astigmatism, especially near
the limbus. The blue arrow
denotes the area where the
conjunctiva– Tenon’s plane is
severely adherent to the
episclera and unable to be
dissected with blunt
instrumentation. At this
juncture, sharp Westcott
scissors are necessary to
continue dissection, as noted
in the next steps.

Method for sharp dissection
• (K) Method for sharp dissection with conjunctival
scarring. Sharp dissection is commonly required
during revision of a trabeculectomy, but rarely
needed during surgery in a primary case.
Successful sharp dissection requires visualization
of the tips of the scissors at all times through the
transparent conjunctiva.

• (K1) Small excursions of the
tips are used; do not open the
tips widely or too much of the
tissue is impaled, leading to a
buttonhole. The black line
outlines where Tenon’s is still
adherent to the underlying
tissue, tethering it down to the
sclera or, in this case, a
plaque of scar tissue over a
preexisting filter. The black
arrow denotes the anterior
extent of the scissor cut. If
the tissue is impaled all the
way to the red arrow, a
buttonhole is sure to occur
because the conjunctiva is
folded underneath, as in

• (K2) This drawing shows
how a buttonhole forms
when too much fibrous
tissue is cut at one time
during a sharp dissection.
The proper way to dissect
with sharp Westcott
scissors is to place the
tips of the scissors on the
area to be incised as in
the black arrows in Fig.
77-9K1 and then flip the
conjunctiva back over the
scissors as in

• (K3) One must know the
location of the scissors at all
times by direct visualization
through the conjunctiva. This
ensures that the conjunctiva is
not perforated prior to closing
the scissors as the tissue is
dissected. The sharp
dissection technique requires
multiple microincisions, not a
large one. As the dissection
progresses, periodically and
repeatedly lift the conjunctiva
up to re-establish orienta

• (K4) Careful sharp
dissection prevents
buttonholes of the
conjunctiva. The
conjunctiva is intact
and the scar tissue over
the previous filter is
easily seen and ready
for dissection.

TECHNIQUE FOR SEPARATING
CONJUNCTIVAL–FIBROUS ADHESIONS
• This technique is very helpful when scar tissue is
encountered during any conjunctival dissection.
The entire technique is dedicated to preventing a
buttonhole in the conjunctiva. During the dissection
with blunt scissors, an impasse was encountered.
The arrow indicates a fibrous adhesion indicating
the need for a slightly different technique.

POSTERIOR DISSECTION OF
TENON’S CAPSULE
• Dissecting a small pocket of Tenon’s capsule
posterior to the proposed bleb site encourages a
posterior flow, and establishes a space for
posterior application of MMC

Posterior dissection of Tenon’s
capsule.
• (L) Separating Tenon’s from
the sclera posterior to the
wound margin will
encourage posterior flow of
aqueous and development
of a diffuse bleb (blue
arrow). This technique
helps to prevent cystic
blebs that tend to migrate
anteriorly. The dissection
should be carried out on
both sides of the superior
rectus muscle, which is not
violated during this
dissection.

ANTIMETABOLITE
• In general, it is better to err on the side of too little
antimetabolite. The reason is simple: once applied,
you can’t take it back. In virgin eyes with a low risk
of failure, some physicians do not use an
antimetabolite (although this trend is becoming
increasingly rare). In this revision, MMC was used
as noted

(M) Subconjunctival application
of mitomycin C.
• (M1) Antimetabolites
are especially important
on filter revisions where
there is increased
tendency for scarring.
Notice the pledget is
pushed posteriorly to
the premade
subconjunctival pocket

(M) Subconjunctival application
of mitomycin C.
• M2) This drawing shows the typical
placement pattern for the sponges,
three in this case. The authors prefer
this placement pattern for fornix or
limbal filters. Currently, the pledgets
are placed posteriorly in order to
encourage flow away from the
limbus. Excessive flow directly over
the fistula is more likely to cause the
bleb to become pale and avascular.
The dose is 0.2 mg/mL for 3 minutes
for most cases. When performing a
combined cataract and
trabeculectomy, one may consider
increasing the MMC exposure time
and/or concentration. After the MMC
is removed, the area is profusely
irrigated.

PARACENTESIS.
• A paracentesis is critical to judging the
characteristics of the filter during surgery (Fig. 77-
9N). In addition, the paracentesis track may be
accessed postoperatively, making it easier to enter
the anterior chamber in a soft eye. It may be easier
to make the paracentesis in a virgin eye after the
flap is dissected anteriorly, as flap creation is much
easier in a normo- tensive environment as opposed
to a hypotensive environment.

Paracentesis.
• (N) The corneal paracentesis
is imperative in filtration
surgery. It helps determine the
flow through the scleral flap.
Once the conjunctiva is
closed, the anterior chamber is
insufflated through the
paracentesis, allowing one to
check for bleb leaks. The
paracentesis is made with a
supersharp blade. Stay
parallel to the iris plane, make
sure the blade is sharp, and
gently enter the anterior
chamber, avoiding the iris and
lens. (

REMOVAL OF SCAR TISSUE
FROM PRIOR FILTER.
• Scar tissue assumes various forms associated with
prior filtration surgery. In this case, a fibrous cap
formed over the filter required removal in order to
gain access to the sclera

(O) Removal of fibrous cap over
prior trabeculectomy site.
• (O1) The back wall of
the fibrous capsule is
incised and dissected
off the sclera.

• (O2) The blue arrow
indicates the fibrous
capsule as it is
dissected anteriorly.
The green arrow is the
conjunctiva–Tenon’s
plane retracted forward.

• (O3) Removal of fibrous
cap that caused the
filter to fail. This is
typical for a
trabeculectomy
revision, which
technically is more
difficult than a virgin
trabeculectomy.

FASHION FLAP
• For the development of a standard flap, refer to
Figure 77-7I–P. There is no difference in flap-making
for either a limbus- or a fornix-based procedure.
The trapezoidal flap is favored during fornix-based
surgery due to its shape, with less posterior space
requirement.

REVISE SCLERAL FLAP
• If the flap is thick and intact, revision is relatively
easy and the flap can be simply resutured back to
the sclera as in Figure 77-7AA. However, in most
revisions, the scleral flap is thin and accessible at
only one point. In this case, a sharp blade was used
to incise the old border, and a cyclodialysis spatula
slid into the anterior chamber to reestablish flow
(Fig. 77-9P). The flap is then closed to allow some
aqueous flow.

(P) Scleral incision and wound
revision
• (P1) Reopen the flap
with a supersharp blade
down almost to the
level of the choroid.
This is only necessary
in one area, as trying to
dissect a thin flap will
cause it to tear,
necessitating a patch
graft.

revision
• (P2) Slide a cyclodialysis
spatula through the
opening to make sure
debris does not clog the
old trabeculectomy
stoma. At this time,
aqueous once again will
start to flow through the
fistula. The spatula is
carefully inserted under
the scleral flap and
guided into the area of
the stoma. (P3

revision
• (P3) Advance the
cyclodialysis spatula into
the anterior chamber to
ensure flow (green arrow).
Do not force the spatula into
the anterior chamber: it
should be an easy entry.
Excessive force implies the
unseen tip of the spatula is
in the wrong position. If the
scleral flap during a revision
is thick and easy to dissect,
this maneuver is not
needed, for the entire old
gap may be dissected,
revealing the old stoma.

FLAP CLOSURE
• The general principle of flap closure is to avoid a
through-and-through hole in the scleral flap while
closing it. This principle holds for all types of
scleral flap closure

(Q) Scleral flap closure
• (Q1) The goal is to
reapproximate the
scleral flap so there will
be controlled leakage of
aqueous through the cut
edge of the flap.

• (Q2) In this revision, the
sclera is thin, which is
the more common
finding during a
revision. The suture,
typically a 10-0 nylon
cutting needle, is
passed through the flap
at a depth of two-thirds
thickness.

• (Q3) If the needle track
goes all the way through
the sclera, a leak may
occur directly through the
needle track leading to
uncontrolled flow through
this site. This may be a
problem, especially if the
suture cheesewires
through the sclera when
the suture is tied, making
the hole larger. On thin
flaps, use 10.0 nylon on a
tapered needle; it creates
a smaller scleral hole. (

WOUND CLOSURE
• The guiding principle in all filtration wound
closures is a watertight finish. In this case a
double-layer closure is used, a routine for all
limbus-based procedures. The double-layer closure
guarantees a watertight wound

(R) Double-layer closure: closure of
Tenon’s capsule and conjunctiva.
• (R1) A double-layer
closure is an added
security against
postoperative leaks.
First, Tenon’s is isolated
and an 8-0 braided
polyglactin suture tied
to it.

• (R2) This is a running,
locking suture. The lock
can be seen at the
green arrow. Tenon’s
tissue acts as a gasket
to prevent leaks.

• (R3) Tenon’s may be
periodically incorporated into
the conjunctival closure if it
looks like the conjunctival
tissue is redundant. This tags
the conjunctiva and pulls it
posteriorly, preventing an
overhanging postoperative
bleb. A 10-0 polyglactin
monofilament suture is used to
close the conjunctiva in a
watertight fashion. The suture
is tightened as it is tied to
assure a tight closure. The
knot is trimmed to prevent
postoperative irritation.

WOUND TEST FOR BLEB
INTEGRITY
• Use the paracentesis site to inject balanced salt
solution into the anterior chamber; the bleb should
insufflate (Fig. 77-9S). Check for leaks and repair as
necessary. If a leak is discovered, use a 2850 nylon
tapered needle (Ethicon) to close the leak. This is a
very small needle that creates only a small opening
in the conjunctiva when passed through. The eye
looked very good on postoperative day 1

(S) Insufflate and check for leaks.
• (S1) The anterior chamber
is insufflated with
balanced salt solution
through the paracentesis
track. Carefully position
the 30-gauge cannula into
the chamber in order to
prevent Descemet’s
detachment. The bleb
should rise as the fluid is
injected, if not, there is a
leak or the flap is too
tight.

(S) Insufflate and check for leaks.
• (S2) Dry the
conjunctival closure
with a Weck-cell sponge
in order to check for
leaks. Leaks are easy to
spot with this technique
and easy to miss
without this technique.
Recheck the bleb and
remove the traction
suture. (

Postoperative day 1.
• (T) The anterior
chamber is deep, the
cornea clear, and the
eye is quiet. A nicely
elevated bleb without
wound leak is present
on day 1. The IOP is
lower than anticipated
at 3 mmHg, but
fortunately resolved
without complications a
week later.

Complications of
Trabeculectomy

Intraoperative Complications of
Trabeculectomy
• Trabeculectomy is performed to achieve lower
intraocular pressure by creating a surgical fistula
to increase aqueous outflow into a conjunctival
bleb. In spite of a well-performed procedure, the
final outcome is unpredictable due to variable and
unknown factors in wound healing leading to bleb
failure. The margin of error in performing
trabeculectomy is very small.

Trabeculectomy
• Every effort should be made to avoid intraoperative
complications. The surgeon should learn and
modify his or her techniques to strive for
perfection. However, if intraoperative
complications occur, one should be able to
recognize them and take appropriate action at the
time of surgery. Some of the important precautions
during surgery are: ■ Avoid subconjunctival
hemorrhage by using a corneal traction suture
instead of a superior rectus traction suture.

Trabeculectomy
• ■ Handle conjunctiva carefully by using nontoothed
forceps or Weck-cel sponge for dissection. Keep it
moist to avoid shrinkage. ■ Obtain good hemostasis
by using pencil-tip cautery in the deep scleral bed
and on the scleral surface but away from the
scleral flap margin. ■ Always look for buttonholes
and wound leaks. The anterior chamber should be
maintained with balanced salt solution and not a
viscoelastic at the conclusion of the surgery.

management of the patient
• The long-term success of trabeculectomy depends in
part on the preoperative and intraoperative
management of the patient. Any intraoperative
complication, if not properly managed, will lead to
failure. Similar to any other operation, trabeculectomy
can be complicated by problems such as anesthetic
issues, poor surgical technique, intraocular
hemorrhage, and postoperative infection. It is
estimated that 50–60% of patients suffer some level of
surgical complication with trabeculectomy.1,2 Most of
these are minor and only require careful observation
and follow-up, but some can lead to ultimate failure of
filtration surgery and/ or permanent vision loss.

management of the patient
• In the majority of cases, the surgeon seeks to
achieve an initial watertight wound closure with
gradual release of the scleral sutures to regulate
the extent of subconjuctival aqueous outflow.
However, the delicate balance between outflow and
healing may be tipped too far in one direction or
the other, thereby leading to either hypotony or
surgical failure of the bleb. The surgeon may
attempt to minimize the unpredictability of the
postoperative course by ensuring meticulous
intraoperative technique.

Intraoperative Complications
• ■ Traction suture
• ■ Hematoma in superior rectus muscle
• ■ Severing of superior rectus tendon
• ■ Cheese wiring of cornea
• ■ Corneal perforation
• ■ Conjunctival flap
• ■ Mishandling of conjunctiva
• ■ Conjunctival buttonhole/tear
• ■ Subconjuctival/episcleral bleeding

• ■ Mitomycin sponge application
• ■ Retained mitomycin sponge after surgery
• ■ Conjunctival buttonhole/tear by sponge
• ■ Scleral flap dissection
• ■ Improper thickness of superficial flap
• ■ Disinsertion of the superficial flap
• ■ Inadvertent early entry into anterior chamber
• ■ Incomplete removal of Descemet’s membrane

• ■ Sclerostomy
• ■ Inadequate/incomplete fistula formation
• ■ Iris/cornea/lens injury
• ■ Corneal injury
• ■ Abrasion and epithelial defect
• ■ Descemet’s membrane detachment
• ■ Iridectomy-related
• ■ Incomplete iridectomy
• ■ Large iridectomy
• ■ Iris incarceration/prolapse
• ■ Iris bleeding/anterior chamber bleeding (hyphema)
• ■ Iridodialysis

• ■ Others
• ■ Lens injury
• ■ Ciliary body injury
• ■ Cyclodialysis
• ■ Vitreous loss
• ■ Shallow anterior chamber
• ■ Conjunctival wound leak
• ■ Serous choroidal detachment
• ■ Suprachoroidal hemorrhage.

Late Failure of Filtering
Bleb

Late Failure of Filtering Bleb
• Late failure of filtration has several causes that range
from blockage of the internal ostium to remodeling of
the filtering bleb to frank scarring of the bleb.
Identifying the cause makes management clear and
likely to be successful. Bleb remodeling occurs within
the first 3–4 months following filtration surgery and can
often be managed conservatively as it may be
transient. Scarring of the episclera with loss of bleb
function may occur anytime from weeks to months or
even years after the initial surgery. Needling using
loupes or at the slit lamp is often successful in this
situation and is a worthwhile in-office treatment to try.
Sometimes, operative revision of the filtration bleb or
repeat filtration at an alternate site is necessary if
needling fails.

Preoperative Evaluation
• The ultimate goal to be wished for with the use of a
glaucoma implant is pressure lowering. Most studies
reported in the literature, with the use of glaucoma
implants, define success as pressures of 21 mmHg or
lower. Most severe glaucoma cases, and this usually
includes most cases in which a glaucoma implant will
be used, require pressures in the low teens, a level
often difficult to obtain with glaucoma implants. The
pressure-lowering effect of the implant depends on the
thinness and permeability of the bleb over the plate.
This can be achieved with the use of antifibrosis
medication, e.g. systemic steroids, or by modification
of the surgical technique, e.g. supra-Tenon’s plate
placement.

Preoperative Evaluation
• Therefore, preoperatively, if a very low pressure needs
to be achieved, the feasibility of the use of systemic
medications such as steroids and non-steroidal anti-
inflammatories needs to be considered. Should the
patient have any medical condition or conditions
precluding systemic antifibrosis medication use, such
as diabetes or hypertension, then modification of the
surgical procedure needs to be considered, and this
will always include the choice of implant to be used.
Supra-Tenon’s placement always needs a single-plate
implant, the ideal size being the single-plate Molteno
implant.

Introduction
• In deciding on the use of glaucoma implants for the
management of uncontrolled intraocular pressure,
a number of important factors need to be taken
into consideration. These factors may be
summarized as follows:
• 1. The underlying cause of the glaucoma.
• 2. The anatomy of the eye and orbit under
consideration.
• 3. Age and ethnicity of the patient.

Introduction
• 4. Previous surgical procedures done in the eye, as
well as any additional pathology that may be
present, such as cataracts or corneal disease.
• 5. Choice of implant, which incorporates the final
intraocular pressure desired to be achieved.

DRAINAGE IMPLANTS
• Drainage implants were originally introduced to treat refractory
glaucomas.2 These included aphakic and pseudophakic
glaucomas, uveitic glaucoma, neovascular glaucoma, glaucoma
associated with corneal transplants, congenital glaucomas due
to iridocorneal dystrophies such as iridocorneal endothelial
dystrophy, and in eyes where previous filters had failed. With
the introduction of the use of antimetabolites, such as 5-
fluorouracil and mitomycin C, many of the conditions mentioned
in this group are now treated with conventional filtering surgery
first. Exceptions include neovascular glaucoma, extensive
scarring of the conjunctiva, and congenital glaucoma with
iridocorneal dysgenesis or with previously failed goniotomy or
trabeculotomy. Aphakic glaucoma and glaucoma associated
with corneal transplants also do better with glaucoma implants.
The 3-year follow-up comparing tube shunt surgery to
trabeculectomy in pseudophakic patients showed a higher
success rate with tube shunts

Choice of Implant
• The questions to be asked regarding the choice of
implants are:
• 1. Do all implants lower the pressure equally,
irrespective of their design?
• 2. Does size matter?
• 3. What important complications are associated
with the different implant?

Choice of Implant
• The overall success rate among five implants
studied, namely, Molteno single and double plate,
Baerveldt, Ahmed, and Krupin implants, was
between 72% and 79%. All five implants decrease
the pressure by 51–62%. There were no
statistically significant differences in either the
percentage change in intraocular pressure (IOP) or
the overall surgical success rate among the five
implants, or within the subdivisions of the Molteno
group based on the size of the end plate.

DOES SIZE MATTER?
• The original single-plate and double-plate Molteno
implants are now rarely used. Newly designed
larger single-plate Molteno implants are now
preferably used. The new single-plate Molteno 3
implant comes in two sizes, 185 mm2 and 245
mm2. The single-plate Ahmed and Krupin implants
are equal at184 mm2. The Baerveldt implant comes
in two sizes, namely 250 mm2 and 350 mm2, the
latter being the same size as the double-plate
Ahmed implant double-plate.

DOES SIZE MATTER?
• The advantages of choosing a small implant are ease
of insertion and that only a single superior quadrant of
the eye is used, leaving the other quadrant available for
a second implant if necessary. A prospective study
comparing the pressure-lowering effect of single- and
double-plate implants confirmed the theory that larger
plates lower the pressure to a greater extent. Perhaps
larger plate size does not result in better IOP control in
the long term, and the standard size single-plate
implant, which is almost identical in the different
implants available, other than the Baerveldt which is
larger, may all have a similar pressure-lowering
potential

PLATE MATERIAL
• The Molteno plate consists of polypropylene,
whereas the Ahmed is either polypropylene or
smooth silicone. The Baerveldt plate is silicone.

COMPLICATIONS
• Postoperative hypotony is a major concern and,
therefore, a decision to prevent this from occurring
needs to be made. The choices are valved or non-
valved implants. The major advantage of valved
implants (e.g. Ahmed, Krupin) is less postoperative
hypotony in most cases, although valve failure can
occur, resulting in hypotony. The major
disadvantage of the valved implants is a more
intense hypertensive phase, with a thicker bleb and
less pressure lowering in the long term. Stenting of
the tubes in non-valved implants may be done to
prevent postoperative hypotony.

Aqueous Shunts: Choice of
Implant
• Since publication of the Tube vs. Trabeculectomy
Study there has been increased interest in the use of
aqueous shunts for the management of glaucoma.
Evidence suggests that long-term IOP control after
aqueous shunts is determined, not only by the size of
the end-plate on the shunt, but also on plate material,
profile and surface texture. Two of the most commonly
used implants are the Ahmed Glaucoma Valve and
Baerveldt Glaucoma Implant. They differ in that the
former has a flow restrictor to minimize early hypotony,
and the latter has a large, smooth flexible plate to
minimize encapsulation.

Baerveldt 350 implant
• Evidence from two recent randomized trials
suggests that the Baerveldt 350 implant gives
lower pressures with fewer glaucoma medications
after 1 year, but at the cost of slightly more
complications. Longer-term data from these trials
are awaited at the time of writing.

BASIC PRINCIPLES
• The basic principles of shunt function include a
permanent sclerostomy, i.e. a tube, usually made of
silicone, placed into the anterior chamber, ciliary
sulcus or vitreous cavity, that drains aqueous to
the equatorial sub-Tenon’s space. To maintain long-
term patency of the distal aperture of the tube, the
opening is surrounded by a plate, usually made of
silicone, of a predetermined surface area. This
plate gradually becomes encapsulated by
surrounding tissue in the weeks after surgery,
resulting in resistance to aqueous flow.

principal problems
• The two principal problems with shunts are firstly,
that the shunt may drain too rapidly in the early
postoperative period, before this capsule develops.
Secondly, the capsule may restrict the absorption
of aqueous to such an extent that the intraocular
pressure (IOP) is not sufficiently well-controlled.

CHOICE OF SHUNT
• Factors that might influence the choice of shunt in
the individual patient include shunt-related factors
such as those that influence the impact of
encapsulation, such as plate surface area and plate
material, and those that affect early IOP control,
such as the presence or absence of a flow resistor.
Patient factors include the type of glaucoma, the
likelihood of hypotony, the presence of
impediments to implantation, such as scleral
buckles, and factors that may influence the degree
of scarring, such as anterior segment
neovascularization.

VALVED VERSUS NONVALVED
• One of the most important features of a shunt is
the presence or absence of a flow restrictor (valved
or nonvalved). Although the flow restrictors in the
former group have not been shown to actually
function as valves, the name has nevertheless
stuck. Valved devices, in theory, allow only
unidirectional flow with a minimum opening
pressure, whereas nonvalved devices are passive,
incapable of influencing flow.

• The Ahmed Glaucoma Valve is an example of the
former, whereas the Molteno Implant and Baerveldt
Glaucoma Implants are examples of the latter. These
implants have a similar lumen diameter (approximately
300 μm). Without a valve, this diameter of tube offers
virtually no resistance to flow and can drain the
anterior chamber completely of aqueous relatively
quickly.
• This does not occur in the early postoperative period
with valved implants because the integral flow
restrictor prevents hypotony in most cases.16,17 With
the Ahmed, the implant must be primed with a fluid
such as balanced salt solution (BSS) in order to
separate and wet the valve leaflets.

• Nonvalved shunts do not contain a flow restrictor and
must be occluded effectively by the surgeon at the time
of implantation, to avoid severe hypotony. A number of
techniques have been described to prevent early
hypotony with nonvalved aqueous shunts. The most
commonly used at the time of writing is external
ligation with an absorbable ligature such as 7/0
polyglactin 910 (Vicryl, Ethicon, Johnson & Johnson
International, Brussels, Belgium). No method has yet
been described that will permit aqueous flow to be
successfully titrated to a clinically safe level with a
ligature. The purpose of ligation is therefore to occlude
the tube completely. Failure to achieve complete
occlusion may result in severe hypotony.

• Successful ligation often results in a high IOP and,
to counteract this, many surgeons additionally
fenestrate the tube proximal to the ligature
(Sherwood slit).18
• A further disadvantage of external ligation is
sudden decompression, usually 5–6 weeks after
surgery when the ligature absorbs. Even if
sufficient encapsulation has developed, the
precipitous drop in pressure in eyes with larger
implants, such as the Baerveldt 350, may be
sufficient to cause a choroidal hemorrhage in a
predisposed individual

THE AHMED GLAUCOMA VALVE
• This implant (Fig. 110-1) is manufactured with a
flexible silicone plate (FP7) or a rigid polypropylene
plate (S2) of similar surface area (184 mm2). The
tube portions are identical and approximately 23-
gauge in external diameter. Versions with smaller
plates designed for pediatric eyes are also
available.

AGV contains a valve mechanism which
must be primed prior to insertion.

THE BAERVELDT GLAUCOMA
IMPLANT
• This implant features a large (250 or 350 mm2) flexible
silicone plate that is noticeably different from the Ahmed, in
that it is thinner, broader, and barium-impregnated
rendering it radio-opaque. The wings of the 350 mm2
implant are usually placed under adjacent rectus muscles.
In order to avoid interference with muscle function, they are
often placed about 1 mm behind the muscle insertion, and
the plate is secured tightly to sclera to avoid movement.
• It is also possible to implant the Baerveldt 101-350 with the
wings on top of the muscles and this is sometimes
performed in patients with extensive scarring, most
commonly after retinal surgery. The 250 mm2 implant has
smaller wings which are not usually tucked under the
muscles.

The arrow shows infused BSS flowing
and demonstrates the large plate
surface area

SURGICAL TECHNIQUE
• The basic surgical technique is similar for all GDDs
(Figure 8). They differ in respect to: • Size of the
conjunctival incision • Methods of flow restriction •
Anterior chamber or pars plana insertion of the
tube.

Surgical Technique 1
(Molteno )

Molteno implants
• Molteno implants (Molteno Ophthalmic Limited,
Dunedin, New Zealand) are surgical devices used in the
treatment of severe and complex cases of glaucoma.
They were developed by Anthony C.B. Molteno and
consist of a fine-bore silicone tube that delivers
aqueous from within the eye onto the surface of an
episcleral plate (Fig. 111-1). The plate is covered by
Tenon’s fascia and conjunctiva, and initiates and
maintains a large circular unilocular bleb. The bleb
develops a specialized fibrovascular lining called the
bleb capsule that becomes distended by aqueous. The
bleb capsule is responsible for regulating aqueous
escape from the eye and is the main determinant of the
final intraocular pressure (IOP) achieved by the
draining implant.

HYPOTENSIVE, HYPERTENSIVE,
AND STABLE STAGES
• The changes that accompany bleb formation
around an implant are most obvious when a single-
plate implant is used to drain severe and advanced
glaucoma in a young adult. Three sequential stages
are described according to the behavior of the IOP
after implant insertion

1. Hypotensive stage
• This stage lasts 7–10 days after operation and is
characterized by low IOP with diffuse edema and
congestion of blood vessels in the tissues covering
the episcleral plate of the implant.

2. Hypertensive stage:
• This stage is characterized by elevated IOP that
peaks at 30–50 mmHg 4–5 weeks after operation (in
untreated cases). As the edema subsides, a
definite layer of fibrous tissue appears in the
deepest layers of the bleb capsule and the bleb
becomes distended with aqueous. However, it is
not until the vascular congestion resolves that the
IOP starts to fall, initially rapidly then more
gradually, to reach a stable plateau 3–6 months
after operation.

3. Stable stage:
• Characterized by a stable IOP and well-
circumscribed bleb with a moderately vascular
fibrous bleb capsule, the stable-stage bleb remains
unchanged for the remainder of the patient’s life.
The thickness of the capsule depends on the
intensity and duration of bleb inflammation during
the hypertensive stage. Trials of anti-inflammatory
fibrosis suppression therapy were undertaken in an
effort to limit inflammation and produce a thin
permeable bleb capsule.

Indications
• Molteno implants are considered in cases where simple drainage
operations such as trabeculectomy are unlikely to provide safe long-
term IOP control. Current indications for using implants include:
• 1. Infantile and juvenile glaucoma.
• 2. Aphakic or pseudophakic glaucoma.
• 3. Traumatic glaucoma.
• 4. Uveitic glaucoma.
• 5. Glaucoma secondary to previous intraocular surgery.
• 6. Neovascular glaucoma.
• 7. Failed previous trabeculectomy .
• 8. Complications of trabeculectomy on the fellow eye.
• 9. Patients intolerant of, or who cannot cooperate with, the medication
regimen.

Molteno3 implant
• Since 2004, evaluation of the Molteno3 implant
suggests that the 175 mm2 Molteno3 implant
should be used in all cases except young patients
and larger eyes in which the 230 mm2 Molteno3
implant is preferred

CHOICE OF SURGICAL
TECHNIQUE
• DELAYED VERSUS IMMEDIATE DRAINAGE OF
AQUEOUS. Molteno implants can be inserted for
delayed or immediate drainage of aqueous. The
advantages of delayed aqueous drainage are such that
the Vicryl tie technique is almost always used.
Immediate drainage of aqueous, however, is necessary
in acutely inflamed eyes and when immediate IOP
reduction is required, e.g. acute neovascular glaucoma,
uveitic glaucoma and when the eye contains blood
after trauma. Photocoagulation of underlying retinal
disease and/or anti-inflammatory fibrosis suppression
therapy can be used to minimize the resulting
hypertensive stage.

Glaucoma management 2016

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Glaucoma management 2016