Download Ahmed Glaucoma Valve and Single

Ahmed Glaucoma Valve and Single-Plate Molteno
Implants in Treatment of Refractory Glaucoma: A
Comparative Study
NADER NASSIRI, GHAZAL KAMALI, MOHAMMAD RAHNAVARDI, BABAK MOHAMMADI, SAMAN NASSIRI,
LALEH RAHMANI, AND NARIMAN NASSIRI
● PURPOSE: To report 2-year follow-up data after Ahmed
valve implantation (New World Medical, Inc) and Molteno single-plate implantation surgical treatment of refractory glaucoma.
● DESIGN: Prospective, randomized, comparative study.
● METHODS: Patients with refractory glaucoma, defined
as uncontrolled intraocular pressure (IOP) of more than
21 mm Hg despite maximal antiglaucoma medication,
previously failed nonseton surgical treatment, or a combination thereof were included. Ninety-two patients were
allocated randomly to each of the study groups and
underwent implantation of either the Ahmed valve implant (model FP7; 184 mm2 surface area) or Molteno
single-plate implant (134 mm2 surface area) and were
followed up for 24 months. Main outcome measures were
IOP and surgical success rate. Other outcome measures
were changes in visual acuity, number of ant-glaucoma
medications, mean deviation of visual field, and rate of
intraoperative and postoperative complications.
● RESULTS: Those who successfully completed the trial
(28 in the Molteno group and 29 in the Ahmed group)
achieved significantly less IOP and fewer glaucoma medications, but worse visual acuity 24 months after surgery.
The Molteno group, compared with the Ahmed group,
achieved significantly lower IOPs after the early postoperative period until the end of the study. Both groups
reasonably maintained visual field during the follow-up.
The rate of surgical failure was comparable in both
groups. Median survival time was 24 months for both
groups. There were no devastating intraoperative or
postoperative complications in either group.
● CONCLUSIONS: Both Ahmed and Molteno implants
successfully preserved visual field, although IOP control
was more pronounced in the Molteno implant group.
(Am J Ophthalmol 2010;149:893–902. © 2010 by
Elsevier Inc. All rights reserved.)
See Accompanying Editorial on page 875.
Accepted for publication Jan 14, 2010.
From the Department of Ophthalmology, Imam Hossein Medical
Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran
(Nad.N., G.K.); and Vanak Eye Surgery Center, Tehran, Iran (M.R.,
B.M., S.N., L.R., Nar.N.).
Inquiries to Nariman Nassiri, Vanak Eye Surgery Center, No. 41,
Haghani Highway, Vanak, Tehran, Iran; e-mail: [email protected]
0002-9394/$36.00
doi:10.1016/j.ajo.2010.01.025
©
2010 BY
H
ISTORICALLY, GLAUCOMA DRAINAGE IMPLANTS
have been reserved for cases of refractory glaucoma deemed at high risk of failure (e.g., eyes
with a previous history of failed trabeculectomy1,2 and with
neovascular and uveitic glaucoma) with standard filtration
surgery. Despite the high-risk profile of these patients,
moderately good levels of success with various types of
glaucoma drainage implants have been observed. Consequently, the use of these implants has increased in recent
years, and they have become the preferred surgical procedure for complex cases.3,4
For more than 2 decades, various types of glaucoma
drainage implants have been developed. These implants
may be subdivided into valved and nonvalved designs.
Those with a nonvalved structure act as an open tube,
which may result in immediate postoperative hypotony5,6
and its attendant complications (e.g., flat anterior chamber, suprachoroidal effusion, and suprachoroidal hemorrhage). Hypotony during the immediate postoperative
period is less common with valved drainages, although it
may still occur.7–10 We investigated the success of the
Ahmed valve implant (New World Medical, Inc, Rancho
Cucamonga, California, USA) and the Molteno singleplate implant (Molteno Ophthalmic Limited, Dunedin,
New Zealand) in treating eyes with refractory glaucoma
during a follow-up period of 24 months.
METHODS
● STUDY SUBJECTS:
A prospective, randomized trial was
performed from January 2003 through August 2005 at 3
medical centers, namely, Imam Hossein Medical Center,
Negah Eye Hospital, and Vanak Eye Surgery Center, all in
Tehran, Iran. The eligibility criteria were refractory glaucoma, defined as uncontrolled intraocular pressure (IOP)
despite maximal antiglaucoma medication, previously failed
nonseton surgical treatment, or a combination thereof. The
exclusion criteria included age younger than 40 years, a visual
acuity of no light perception, lens opacity, elevated IOP
associated with silicone oil, previous glaucoma drainage
device implantation in the same eye, previous cyclodestructive treatment, increased risk of endophthalmitis (e.g., active
adnexal and ocular surface infection, immunosuppression, or
ELSEVIER INC. ALL
RIGHTS RESERVED.
893
Of 101 eligible patients, 92 (91.0%) agreed to participate. Study subjects were assigned randomly to either the
Ahmed or Molteno groups. Randomization was performed
using a random permuted block design with a block size of
2, stratified for age, sex, and hosting medical center.
Neither patients nor investigators were masked to study
groups. Figure 1 shows a flow chart of the trial. Operations
were all performed by the same senior right-handed surgeon (Nad.N.). To reduce the risk of potentially permanent visual loss, all patients underwent surgery within 4
weeks of enrolling in the trial. Before operation, the
exclusion criteria again were reviewed by the surgeon.
● PREOPERATIVE AND POSTOPERATIVE ASSESSMENTS:
Presurgical assessments included slit-lamp biomicroscopic
examination, funduscopy, Snellen visual acuity (VA), baseline IOP, number of antiglaucoma medications, and Humphrey perimetry results. Follow-up visits were scheduled at
day 1, week 1, and months 1, 3, 6, 9, 12, 18, and 24, and more
often when necessary. Postoperative evaluations included
assessment of visual acuity, IOP (in millimeters of mercury),
number of antiglaucoma medications, lens opacity, and postoperative complications. Humphrey perimetry was performed
at postoperative months 3 and thereafter. A formal motility
evaluation was performed in all patients at baseline and at the
1-year and 2-year follow-up visits, as well as during any visits
after 3 months if the patient reported diplopia.
The best-corrected visual acuity was measured using a
Snellen chart (CP-690; Nidek Co, Ltd, Gamagori Aichi,
Japan) calibrated for a 20-foot (approximately 6 m) distance by the line assignment method within the month
before the surgery; the figures were converted to logarithm
of the minimal angle of resolution notation by the standard
conversion table. IOP was measured using a Goldman
applanation tonometer (AT-900; Haag-Streit AG, Koniz,
Switzerland) mounted on a slit lamp; if required, gonioscopy (Haag-Streit AG) also was performed. The preoperative IOP for each eye was considered as the last measure
before operation.
24 –2 threshold visual field assessment was performed with
the Humphrey Field Analyzer (Allergan-Humphrey Instruments, San Leandro, California, USA). The mean deviation—a visual field index provided by Statpac-2 (AllerganHumphrey Instruments)13 and determined from a comparison
with an age-matched normal population—was available as a
global assessment of visual field damage. We considered the
phenomenon of learning effect in our analysis of mean
deviation; this is a phenomenon whereby the baseline visual
field is worse than in subsequent tests,14,15 so using baseline
tests may result in a false-positive defect being compared with
actual glaucomatous progression or the development of a
cataract, and not stable fields. To avoid this, we included only
results where consecutive field tests did not show an improvement of 2 dB or more in the mean deviation over the baseline
reading.
FIGURE 1. Trial flow chart, the Ahmed valve and Molteno
implant groups. A ⴝ analyzed; CS ⴝ complete success; F ⴝ
intervention failure; L ⴝ lost to follow-up; QS ⴝ qualified
success.
immunodeficiency, including the use of systemic steroids),
posterior segment disorders, or pre-existing ocular comorbidities (e.g., pterygium, phacodonesis, corneal opacity, or corneal endothelial dystrophies). Only 1 eye per patient was
included in this trial.
An estimation of sample size was performed considering a
study power of at least 0.8 with an ␣ error of 0.05 aiming to
detect a difference of 1 mm Hg in mean IOP in the
postoperative month 24 between the 2 groups. Mean IOP in
the postoperative month 24 was estimated to be 15 mm Hg in
the Ahmed group based on the results of the previous
studies.11,12 Based on this estimation, a total of 64 study
subjects was deemed adequate, and considering a total of 30%
assumed dropout and failure rate during the follow-up, recruitment of at least 92 study subjects was targeted.
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● OUTCOME MEASURES:
IOP (primary outcome measure), number of antiglaucoma medications, visual acuity,
visual field, and surgical failure were considered as measures assessing efficacy; intraoperative and postoperative
complications were considered as measures assessing safety.
Surgical failure was defined as persistent IOP of more than
21 mm Hg on maximally tolerated medications or IOP less
than 6 mm Hg on 2 consecutive visits, phthisis bulbi,
reduction of vision to no light perception, removal of the
shunt implant, reoperation for glaucoma, or any devastating intraoperative or postoperative complication.11,16 Reoperation was defined as additional glaucoma surgery
requiring a return to the operating room, such as placement of a tube shunt. Interventions performed at the slit
lamp, such as needling procedures, were not considered
reoperations. Surgical revision of the glaucoma shunt
implants for other postoperative reasons (e.g., tube repositioning or repair of conjunctival wound dehiscence) were
recorded, but were not considered surgical failures. Devastating complications included suprachoroidal hemorrhage
that threatened visual fixation, was likely to develop a
kissing appearance, or both; malignant glaucoma; endophthalmitis; retinal detachment; chronic hypotony; or serous
choroidal effusions necessitating surgical drainage or that
had a kissing appearance.
Treatment success was subdivided into complete and
qualified. A complete success was defined as IOP between
6 and 21 mm Hg without any antiglaucoma medication,
and qualified success was defined as IOP between 6 and 21
mm Hg with 1 medication or more. Hypotony was defined
as an IOP of less than 6 mm Hg on 2 consecutive
visits;10,12,16 a hypertensive phase was defined as an IOP of
more than 21 mm Hg during the first 3 postoperative
months (with or without medications) after a reduction in
IOP to less than 22 mm Hg during the first postoperative
week and not caused by tube obstruction, retraction, or
valve malfunction.17 Resolution of this phase was IOP of
less than 22 mm Hg along with a reduction of the IOP by
3 mm Hg or more with the same or fewer number of
medications, or reduction of at least 1 medication with a
change in of IOP less than 3 mm Hg.17
● PROCEDURE:
The tube shunts used were either the
valved 184-mm2 surface area Ahmed Glaucoma Valve
(AGV Model FP7) or the 134-mm2 surface area single-plate
Molteno implant. Before the trial, the surgeon made a
transition from the polypropylene (model S2) to the silicone
(model FP7) Ahmed valve. Recent studies have reported
significantly lower failure rates with silicone valves.18 –21
General anesthesia was given in most cases; in some cases, a
peribulbar block consisting of lidocaine 2% (Xylocaine;
AstraZeneca, Cheshire, United Kingdom) with hyaluronidase (Hyalase; Wockhardt Ltd, Wrexham, United Kingdom) was used. Immediately before surgery in the operating
room, povidone–iodine 5% was applied to the skin of the
eyelids of the operative eye, nose, and forehead. The operaVOL. 149, NO. 6
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TABLE 1. Demographic and Baseline Characteristics of
Study Subjects from the Ahmed Valve Implant and
Molteno Single-Plate Implant Groups
Characteristics
Ahmed Valve
Implant
(n ⫽ 46)
Molteno
Single-Plate
Implant
(n ⫽ 46)
Demographic characteristics
Mean age (SEM), yrs
59.4 (1.51)
63.3 (1.62)
Male/female, n
25/21
22/24
Background conditions, n
(%)
Diabetes mellitus
11 (23.9)
11 (23.9)
Hypertension
13 (28.3)
13 (28.3)
Family history of
glaucoma
11 (23.9)
10 (21.7)
Bilateral glaucoma
12 (26.1)
14 (30.4)
Previous glaucoma
treatments, n (%)
Penetrating iridectomy
8 (17.4)
9 (19.6)
Trabeculectomy
17 (37.0)
18 (39.1)
No. of trabeculectomy
procedures
1
1 (2.2)
1 (2.2)
2
14 (30.4)
14 (30.4)
3
2 (4.3)
3 (6.5)
Enrolled eye baseline
features
Side, right/left, n
24/22
20/26
Lens group, n (%)
Phakic
31 (67.4)
33 (71.7)
Aphakic
6 (13.0)
7 (15.2)
Pseudophakic
9 (19.6)
6 (13.0)
Subtypes of glaucoma, n
(%)
Failed filtration
17 (37.0)
19 (41.3)
Pseudoaphakia
9 (19.6)
6 (13.0)
Neovascular
9 (19.6)
12 (26.1)
Aphakia
6 (13.0)
6 (13.0)
Uveitic
5 (10.9)
3 (6.5)
Mean IOP (SEM), mm Hg
32.11 (1.32) 32.41 (1.27)
Mean BCVA (SEM), logMAR
units
0.64 (0.09)
0.61 (0.09)
Visual field mean deviation
(SEM), dB
–18.57 (0.82) –19.11 (0.79)
Mean no. of glaucoma
medications (SEM)
2.7 (0.08)
2.7 (0.09)
P
Value
.08
.67
1.00
1.00
1.00
.82
1.00
1.00
.98
.53
.69
.82
.87
.86
.64
.72
BCVA ⫽ best-corrected visual acuity; dB ⫽ decibels; IOP ⫽
intraocular pressure; logMAR ⫽ logarithm of the minimal angle
of resolution; SEM ⫽ standard error of mean.
tive eye was draped in the usual manner for ophthalmic
surgery. In both types of shunts, a clear corneal traction suture
was placed with silk 7-0, and the fornix-based conjunctival
flap and Tenon capsule were fashioned supratemporally. To
prime the valve, the tube of the shunt was irrigated with a
balanced saline solution (BSS; Alcon, Fort Worth, Texas,
MOLTENO IMPLANT
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TABLE 2. Preoperative and Postoperative Month 24 Figures in Those Study Subjects from the Ahmed Valve Implant and
Molteno Single-Plate Implant Groups Who Successfully Completed the Trial
Ahmed Valve Implant (n ⫽ 29)
Mean IOP (SEM), mm Hgb
Mean BCVA (SEM), logMAR units
Visual field mean deviation (SEM), dBc
Mean no. of glaucoma medications (SEM)
Molteno Single-Plate Implant (n ⫽ 28)
Preoperative
Month 24
P Valuea
Preoperative
Month 24
P Valuea
30.81 (1.67)
0.66 (0.12)
⫺19.70 (0.96)
2.8 (0.11)
17.00 (0.23)
0.78 (0.12)
⫺19.67 (0.95)
1.03 (0.27)
⬍0.001
0.001
0.09
⬍0.001
33.06 (1.66)
0.59 (0.12)
⫺18.45 (1.11)
2.7 (0.11)
15.36 (0.33)
0.70 (0.11)
⫺19.49 (1.17)
1.41 (0.19)
⬍.001
⬍.001
⬍.001
⬍.001
BCVA ⫽ best-corrected visual acuity; dB ⫽ decibels; IOP ⫽ intraocular pressure; logMAR ⫽ logarithm of the minimal angle of resolution;
SEM ⫽ standard error of the mean.
a
Wilcoxon signed-rank test comparisons of postoperative month 24 and preoperative figures in each study group, post hoc study powers
for all significant comparisons were ⬎80% (based on an ␣ error of 0.05).
b
P ⬍ .001, Mann–Whitney U test comparison of postoperative month 24 figures between the 2 study groups.
c
Three subjects in the Ahmed group and 5 in the Molteno group were excluded from visual field calculations because of the learning effect,
reducing total number to 26 in the Ahmed group and 23 in the Molteno group.
USA). The plate was secured 8 to 9 mm posterior to the
surgical limbus with interrupted 7-0 nylon sutures using
tapered cutting needles.
In the Molteno implant group, the anterior chamber
drainage tube was occluded by tying a 7-0 Vicryl suture
(Ethicon, Norderstedt, Germany) around its exterior, where
it joined the plate of the implant, to restrict the flow through
the device temporarily until encapsulation of the plate occurred. Fenestrations were placed anterior to the suture using
a 28-gauge needle to allow leakage of the aqueous, providing
initial IOP control. Next, in both groups, the tube was
trimmed to extend approximately 2 to 3 mm beyond the
surgical limbus with the bevel facing up; it then was entered
into the anterior chamber by a 23-gauge needle parallel to the
iris plane. If a peripheral iridectomy was present from a
previous surgery, the needle tract was placed slightly to one
side of the iridectomy. Sodium hyaluronate (Healon, 10
mg/mL; Advanced Medical Optics, Santa Ana, California,
USA) was injected to prevent sudden collapse of the
anterior chamber. The tube was inserted with smooth
forceps through the needle tract, ensuring that no iris or
corneal touch occurred. In patients with aphakic and
pseudophakic glaucoma who had vitreous in the anterior
chamber, an anterior vitrectomy was performed before the
placement of the tube. The tube then was anchored to the
sclera using a 10-0 nylon suture and was covered with a
rectangular piece of donor scleral patch graft. The conjunctiva was closed using 10-0 interrupted nylon sutures. A
clear cornea paracentesis then was created to remove the
Healon as much as was possible, and the anterior chamber
then was reformed with BSS. At the end of surgery,
subconjunctival injections of antibiotics and corticosteroids were administered away from the surgical site. No
adjunctive antimetabolite was used in any of the cases.
Postoperative management consisted of combination topical antibiotic and steroid eye drops, which were tapered
over the course of 6 to 8 weeks. Antiglaucoma medications
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FIGURE 2. Graph showing the mean preoperative and postoperative intraocular pressures in the Ahmed valve and Molteno
implant groups. *P < 0.001, **P ⴝ 0.001, ***P < 0.01,
Mann–Whitney U test comparisons of the figures at the
different time points between 2 groups.
were removed or added as needed, depending on the IOP
and clinical status of the operated eye.
● STATISTICAL ANALYSIS: Preoperative and postoperative measures were compared within and between study
groups. Quantitative variables were compared using nonparametric tests, that is, the Mann–Whitney U test or
Wilcoxon signed-rank test, whichever appropriate. The
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FIGURE 3. Graph showing the preoperative and postoperative mean number of glaucoma medications in the Ahmed valve and
Molteno implant groups. Note that comparisons at all time points between 2 groups were insignificant.
FIGURE 4. Graph showing visual acuity in the Ahmed valve and Molteno implant groups. Note that comparisons at all time points
between 2 groups were insignificant. logMAR ⴝ logarithm of the minimal angle of resolution.
chi-square and Fisher exact tests were used for qualitative
variables. To determine factors independently associated
with IOP in postoperative month 24, multivariate analysis
was performed using a stepwise linear regression model of
several variables. The cumulative probability of success was
analyzed by Kaplan-Meier life-table analysis. As soon as an
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AHMED VALVE
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eye reached a failure end point, it was censored from further
analysis. Cox proportional hazards analysis was used to identify independent predictors of surgical failures. Post hoc study
power for significant comparisons was calculated using
G*Power 3, a power analysis software.22 P values less than .05
were considered statistically significant.
MOLTENO IMPLANT
897
TABLE 3. Postoperative Complications after Ahmed Valve
Implantation and Molteno Single-Plate Implantation
Complications
Hyphema ⬎ 1 mm
Wound dehiscence
Choroidal effusion
Choroidal maculopathy
Flat anterior chamber
Obstruction of tube
By fibrin
By clot
Tenon cyst
Cataract formation
Ahmed Valve
Implant
(n ⫽ 46)
Molteno
Single-Plate Implant
(n ⫽ 46)
P
Valuea
3 (6.5)
2 (4.3)
2 (4.3)
0 (0)
1 (2.2)
2 (4.3)
2 (4.3)
4 (8.7)
1 (2.2)
2 (4.3)
1.00
1.00
.67
1.00
1.00
2 (4.3)
0 (0)
13 (28.3)
5 (10.9)
1 (2.2)
1 (2.2)
11 (23.9)
8 (17.4)
1.00
1.00
.83
.55
Data are presented as n (%).
a
Fisher exact test.
FIGURE 5. Kaplan-Meier survival curve analysis of event-free
rates among the Ahmed valve and Molteno implant groups.
● SURGICAL FAILURE AND SURVIVAL ANALYSIS:
Both
groups were comparable in terms of surgical failures. There
were a total of 7 failures (1 failed filtration, 3 uveitic, 1
aphakia, 1 neovascular, and 1 pseudoaphakia) in the
Ahmed group at a mean postoperative time of 11.6 ⫾ 4.7
months and 5 failures (1 failed filtration, 1 uveitic, 1
pseudophakia, 2 neovascular) in the Molteno group at a
mean postoperative time of 12.0 ⫾ 8.7 months. All
surgical failures were the result of uncontrolled glaucoma
(IOP ⬎ 21 mm Hg) with the maximally tolerated antiglaucoma medications. Qualified and complete rates of
success at 12 months and 24 months after operation were
comparable between both groups (Figure 1).
In Kaplan-Meier survival analysis, median survival time
was 24 months for both the Ahmed and Molteno groups
(P ⫽ .65, log-rank test). The cumulative probability of
success at 1 and 2 years was 88% and 82% in the Ahmed
group, respectively, and 93% and 84% in the Molteno
group, respectively (Figure 5).
Univariate Cox proportional hazards analysis could not
identify any independent predictor of operation failure among
several variables tested, including study group (Ahmed vs
Molteno) and other variables as listed in Table 1. In multivariate analysis of the same variables, the Ahmed valve
(regression coefficient, 1.69; 95% confidence interval, 0.91 to
2.47) and hypertension (regression coefficient, 0.90; 95%
confidence interval, 0.02 to 1.79) were associated independently with higher IOP in postoperative month 24.
RESULTS
BASELINE VARIABLES WERE COMPARABLE IN BOTH GROUPS
(Table 1). Those who successfully completed the trial in
both groups (28/46 [60.9%] in the Molteno group and
29/46 [63.0%] in the Ahmed group; Figure 1) achieved
significantly lower IOP and fewer glaucoma medications,
but worse visual acuity 24 months after operation in
comparison with their preoperative measures (Table 2).
● INTRAOCULAR PRESSURE AND OTHER EYE FEATURES:
IOP was significantly lower in the Ahmed group than in the
Molteno group in postoperative day 1 and week 1. Nevertheless, the Molteno group showed markedly lower IOPs thereafter up to the end of the study in postoperative month 24
(Figure 2). The Molteno group, compared with Ahmed
group, showed significantly higher mean (⫾ standard deviation) percentages of change from preoperative IOP to postoperative month 12 IOP (⫺50.7 ⫾ 11.6% vs ⫺41.4 ⫾
13.9%; P ⫽ .004; post hoc study power, 91%) and month 24
IOP (⫺49.7 ⫾ 11.6% vs ⫺41.9 ⫾ 14.6%; P ⫽ .049; post hoc
study power, 71%). Meanwhile, the number of glaucoma
medications after operation was not significantly different
between the 2 groups (Figure 3).
Visual acuity deteriorated in both groups during the
2-year follow-up and there were no significant betweengroup differences at any point during the study (Table 2;
Figure 4). In postoperative month 24, the mean deviation
of visual field results remained comparable with the preoperative value in those who successfully completed the
trail in the Ahmed group. However, the Molteno group
experienced worsened mean deviation of the visual field
results in postoperative month 24 than before surgery
(Table 2).
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● HYPERTENSIVE PHASE:
A hypertensive phase was observed in 13 eyes (28.3%) after a mean of 5.5 ⫾ 1.7 weeks
(median, 4 weeks, range, 1 to 11 weeks) in the Ahmed
group. The mean IOP at the time of onset was 31.1 ⫾ 4.3
mm Hg, with an average number of antiglaucoma medications of 1.8 ⫾ 0.6. Of the 13 hypertensive eyes in the
Ahmed valve group, resolution occurred in 4 eyes within
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10 months, and no other resolution occurred thereafter;
treatment failed in 3 eyes, and in the remaining 6, IOP was
controlled (⬍21 mm Hg with medications) at the follow-up visits, but did not meet the criteria for resolution.
In the Molteno group, a hypertensive phase was observed
in 8 eyes (17.4%) after a mean of 6 ⫾ 1.3 weeks (median,
5 weeks; range, 3 to 12 weeks). The mean IOP at the time
of onset was 30.6 ⫾ 3.22 mm Hg, with an average number
of antiglaucoma medications of 1.6 ⫾ 0.5. No resolution
observed in the hypertensive eyes of the Molteno implant
group: 2 failed and 6 continued using the same number of
antiglaucoma medications without any improvement in
IOP control.
● INTRAOPERATIVE AND POSTOPERATIVE COMPLICATIONS: There were no major intraoperative complica-
tions. Postoperative complications were comparable in
both groups (Table 3); there was no case of hypotony or
devastating complications in both groups. 5-Fluorouracil
was not applied for any patient after surgery. Bleb needling
was performed in 10 (21.8%) and 9 (19. 6%) patients in
the Ahmed and Molteno groups, respectively. No vision
loss to no light perception was observed.
DISCUSSION
THIS RANDOMIZED CLINICAL TRIAL WAS DESIGNED TO IN-
vestigate the success of the Ahmed valve compared with
the Molteno implant in the surgical management of eyes
with refractory glaucoma.
● INTRAOCULAR PRESSURE
MEDICATIONS: After 2 years
AND
ANTIGLAUCOMA
of follow-up, the level of
IOP control was 49.7% and 41.9% in the Molteno and
Ahmed groups, respectively. The Molteno group, compared with the Ahmed group, showed higher IOPs in
postoperative day 1 and week 1. From postoperative month
1 until the end of the trial, IOP remained significantly
lower in the Molteno group than in the Ahmed group.
This is despite a comparable number of antiglaucoma
medications between the 2 groups. The higher IOPs
(Figure 2), mean number of antiglaucoma medications
(Figure 3), and earlier administration of medications (Figure 3) within the first postoperative month in the Molteno
group can be attributed to the temporary restriction of
aqueous outflow by the absorbable ligature in the immediate postoperative period.
The degree of IOP reduction after glaucoma drainage
implant surgery may be dependent on capsular thickness
and the total surface area of encapsulation. Lower postoperative IOP is expected with a thinner capsule and larger
surface area of the drainage device. It has been reported
that shunts with a larger surface area (e.g., the double-plate
Molteno implant) may provide better IOP control,23,24
although early hypotony-related complications may be
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more likely with these shunts. Nevertheless, there seems to
be an upper limit to plate size beyond which other factors,
such as the degree of encapsulation around the end plate,
influence the final IOP. However, the ideal size of the end
plate has not been identified precisely.25–32
● VISUAL ACUITY AND VISUAL FIELD: Both groups
showed approximately 1 Snellen line of deterioration in
visual acuity, which is compatible with that reported in
previous studies.9,10,12,33–35 This may be attributed to the
progression of visual field defect, to the progression of lens
opacity, which has been reported to be higher in glaucomatous eyes secondary to glaucoma surgery36 – 41 and antiglaucoma drug therapy,42– 44 or both.
Whereas the final visual field score in the Ahmed
group was not significantly different from the baseline
value, the Molteno group had an approximately 1-dB
loss in mean deviation score after 24 months, which was
statistically significant (Table 2). Ironically, this happened despite lower mean postoperative IOPs achieved
in the Molteno group than in the Ahmed group. We
believe that this level of decrease in mean deviation in
the Molteno group cannot be of clinical importance and
may be attributed to decreasing visual acuity (Table 2)
and increasing lens opacity (Table 3). Additionally, the
Molteno group, compared with the Ahmed valve group,
had poorer control of immediate postoperative IOPs,
which may have resulted in deteriorated visual field
results in the earlier postoperative period and resulted in
poorer final visual field results despite better final
general IOP control in the former group. Early postoperative IOP control may result in better visual field
preservation, especially in those with severe glaucoma.
Nevertheless, visual field assessment was not carried out
during the first 3 postoperative months of the current
study, and further studies are required to investigate this
hypothesis. It seems that the achieved level of IOP
control in both groups of this study was clinically
sufficient to preserve visual field defect after 24 months.
● SURVIVAL ANALYSIS: Survival analysis did not show
any significant difference between the 2 groups. The
surgical success rate at the end point of this study was more
than 80% in both groups. Surgical success rates for glaucoma drainage devices have been reported to be 22% to
100%.45 However, it is difficult to perform an accurate
comparison between various studies because most clinical
data were derived from retrospective studies with various
demographic and surgical characteristics. Additionally,
some results involving the Ahmed valves may not be valid
for current practice because of the change from the
polypropylene to the silicone Ahmed valves by many
surgeons. The annual success rate decrement was 6% in
the Ahmed group and 9% in the Molteno group, which
seems to be less than the previously reported 10% to
15%.30,46
MOLTENO IMPLANT
899
● HYPERTENSIVE PHASE:
A hypertensive phase, as an
early finding, has been reported after implantation of both
the Molteno implant and Ahmed valve9,10,17,24,30,47; however, it is less common with nonvalved glaucoma drainage
devices,17,31 mostly because of the widespread use of
intraoperative tube ligation. The hypertensive phase was
observed in 13 (28.3%) patients in the Ahmed group,
which was less than previously reported rates of 84%,30
56%,17 and 50%.19 It is also less than that of our previous
study (29.3%), where we used the same definition for
hypertensive phase17 and reported the outcome of combined Ahmed valve drainage (model S2) and phacoemulsification.48 This may be because of the use of Ahmed
valves with silicone material (FP7 model) in the current
study. It has been shown previously that Ahmed valve
tubes with polypropylene have a greater risk of encapsulation.17,20,21,30 Conversely, Mackenzie and associates reported a similar incidence of hypertensive phase in silicone
and polypropylene material Ahmed valves.19
Although the Ahmed valve model FP7 has silicone
material and a relatively larger (185 mm2) and more
flexible end plate compared with the polypropylene model
and the smaller (134 mm2) end plate of the Molteno
implant, the incidence of a hypertensive phase was lower
in the Molteno group compared with the Ahmed group
(17.4% vs 28.3%). The explanation may lie in the immediate aqueous filtration that occurs with Ahmed valves
and the delayed filtration with the ligated Molteno
implants.11,31 Additionally, the rate may have been underestimated in our study because of the earlier administration
of antiglaucoma medication in the Molteno group, compared with the Ahmed group.
Resolution was observed in 4 of 13 patients and 0 of 8
patients in the Ahmed and Molteno groups, respectively.
This supports the conclusions of Nouri-Mahdavi K and
Capriole, who suggested that the so-called hypertensive
phase is actually transient in a minority of the eyes and
that most patients will need medication for at least the first
postoperative year.17 They reported better IOP control and
a significantly lower number of medications in the group
without a hypertensive phase. However, Mackenzie and
associates observed resolution of the hypertensive phase in
most patients.19 This may be the result of the preference in
that study for the application of bleb needling with
5-fluorouracil. Our preference in the management of the
hypertensive phase was for administration of antiglaucoma
medications rather than bleb needling.
ate aqueous filtration through the Ahmed valve can
stimulate a fibrotic response to inflammatory factors in the
subconjunctival space, delayed flow with a ligated nonvalved implant may elicit a less fibrous reaction.11 Other
factors, such as biomaterial characteristics, shape, and end
plate consistency, which differ with different devices, have
been linked to different rates of encapsulated blebs.20,21 In
contrast to Wilson and associates, we reported all eyes with
an encapsulated bleb regardless of whether the IOP was
more or less than 21 mm Hg.12 This complication was
managed initially by adding antiglaucoma medications and
then by needling49 without an adjunctive antimetabolite.
Bleb needling was performed in 10 patients in the Ahmed
valve group and in 9 patients in the Molteno implant
group.
All cases with choroidal effusion and choroidal maculopathy responded to medical therapy with a corticosteroid. Those with conjunctival wound dehiscence were
repaired with resuturing, and this was not considered a
surgical failure. One patient with a flap anterior chamber in
the Molteno group required reformation with viscoelastic.
There were no ocular motility problems in either group.
Hyphema was transient and inconsequential. Obstruction of
the tube with fibrin was managed with corticosteroids. Cataract was responsible for loss of 2 Snellen lines or more in 6
(13%) and 8 (17.4%) phakic eyes in the Ahmed and
Molteno groups, respectively. Gedde and associates reported
higher rates of cataract progression (loss of ⱖ 2 Snellen lines)
after 350-mm2 Baerveldt glaucoma implant administration
(33%) and trabeculectomy (48%).36
With its relatively stringent inclusion and exclusion
criteria, the study findings may not be applicable to all
refractory glaucoma patients. Final analysis was performed
on 59 study subjects, which is short of the 64 subjects that
were deemed required by sample size estimation. However,
the post hoc calculated power of the study was satisfactory,
and the actual difference in mean IOP in postoperative
month 24 between the 2 groups was more than the
estimated figure of 1 mm Hg, which makes this shortfall
less detrimental to the final conclusions. With the limited
number of patients in this trial, we could not investigate
accurately all the factors that may have influenced outcome and eventually can affect choice of glaucoma drainage implant before surgery. The trial data were analyzed
according to the protocol, which potentially may affect the
results and might have been a source of bias.
In conclusion, this study corroborates previous findings
regarding the success of both the Ahmed and Molteno
groups in the surgical management of patients with refractory glaucoma. Both studied glaucoma drainage implants
were comparable in survival analysis, surgical complications, and visual field stabilization. However, the Molteno
group had better IOP control after the immediate postoperative period, and this device may be a better choice,
especially in eyes with advanced glaucoma where more
IOP reduction is required.
● INTRAOPERATIVE AND POSTOPERATIVE COMPLICATIONS: There were no intraoperative or devastating post-
operative complications. All complications were transient
and resolved spontaneously or with simple medical or
surgical interventions; so, they were not considered to be
surgical failures. The most common postoperative complication was an encapsulated bleb, which occurred more
frequently with Ahmed valve implants. Whereas immedi900
AMERICAN JOURNAL
OF
OPHTHALMOLOGY
JUNE 2010
THE AUTHORS INDICATE NO FINANCIAL SUPPORT OR FINANCIAL CONFLICT OF INTEREST. INVOLVED IN DESIGN OF STUDY
(Nad.N., G.K., S.N., L.R, Nar.N.); Conduct of study (Nad.N., G.K., S.N., L.R., Nar.N.); Data collection (G.K., S.N., L.R.); Analysis and interpretation
of data (M.R., B.M., Nar.N.); Preparation of the primary article or its critical revision (Nad.N., G.K., M.R., B.M., S.N., L..R, Nar.N.); Preparation of
subsequent revisions (Nad.N., M.R., Nar.N.); and final approval of the article and its revisions (Nad.N., G.K., M.R., B.M., S.N., L..R, Nar.N.). The
Ethics Committee of the Shaheed Beheshti University (M.C.), Tehran, Iran, and institutional review board at each clinical center (i.e., Imam Hossein
Medical Center, Negah Eye Hospital, and Vanak Eye Surgery Center, Tehran, Iran) approved the study protocol. All patients provided informed consent
in accordance with local regulations and the Declaration of Helsinki. The study is registered with ClinicalTrials.gov (registration no. NCT00971061).
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