Original Article

Effect of Phacoemulsification on Intraocular Pressure
in Eyes with Functioning Tube Shunts

Wesam Shamseldin Shalaby1,2, MD; Sonali Patel3, BS; Sophia S. Lam3, BS; Allen Ganjei4, BS; Aakriti Garg
Shukla1, MD; Natasha Kolomeyer1, MD; Daniel Lee1, MD; L. Jay Katz1, MD; Marlene R. Moster1, MD; Jonathan

Myers1, MD; Reza Razeghinejad1, MD

1Wills Eye Hospital, Glaucoma Research Center, Philadelphia, PA, USA
2Tanta Medical School, Tanta University, Tanta, Gharbia, Egypt

3Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
4College of Medicine, Drexel University, Philadelphia, PA, USA

ORCID:
Wesam Shamseldin Shalaby: https://orcid.org/0000-0003-2577-9412

Reza Razeghinejad: https://orcid.org/0000-0001-7961-8425

Abstract
Purpose: To evaluate the effect of phacoemulsification on intraocular pressure (IOP) in eyes with
functioning tube shunts.
Methods: This was a retrospective chart review of primary open-angle glaucoma (POAG) patients
with a functioning tube who underwent phacoemulsification and had ≥24 months of follow-up.
The primary end point was defined as surgical failure (IOP > 21 mmHg) at month 24, progression
to no light perception (NLP) vision, glaucoma reoperation, or implant removal. Surgical failure
defined as IOP >18 and >15 mmHg, changes in visual acuity (VA), IOP, and number of medications
were assessed.
Results: Twenty-seven eyes of 27 patients with moderate or severe POAG were included. The
mean age of the patients was 64.2 ± 10.8 years. The interval between the tube shunt and
phacoemulsification was 28.8 ± 25.0 months. At the end of the study, four (14.8%) eyes met the
failure criteria; the average time to failure was 9.3 ± 3.8 months. The causes of failure were high
IOP in two (50.0%) and glaucoma reoperation in two (50.0%) eyes; however, no eyes progressed
to NLP vision. Surgical failure defined as IOP >18 and >15 mmHg showed an increasing failure
rate (18.5% and 48.5%, respectively). The mean IOP and medications number remained stable
at month 24 compared to baseline (P = 0.131 and P = 0.302, respectively). Initially, VA showed
improvement, with the greatest improvement at 6 months (P = 0.001), but at 24 months the
improvement was no longer significant (P = 0.430).
Conclusion: Phacoemulsification in patients with functioning tubes did not change the mean IOP
in most of the patients (86.2%); the number of medications also did not increase.

Keywords: Cataract Extraction; Glaucoma Drainage Implants; Intraocular Pressure; Phacoemulsification

J Ophthalmic Vis Res 2023; 18 (2): 150–156

Correspondence to:

Wesam Shamseldin Shalaby, MD. Glaucoma Research
Center, Wills Eye Hospital, 840 Walnut St., Suite 1140,
Philadelphia, PA 19107, USA
Email: wshalaby@willseye.org
Received: 25-10-2021 Accepted: 30-08-2022

Access this article online

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DOI: 10.18502/jovr.v18i2.13180

This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

How to cite this article: Shalaby WS, Patel P, Lam SS, Ganjei
A, Shukla AG, Kolomeyer N, Lee D, Katz LJ, Moster MR, Myers
J, Razeghinejad R. Effect of Phacoemulsification on Intraocular
Pressure in Eyes with Functioning Tube Shunts . J Ophthalmic Vis
Res 2023;18:150–156.

150 © 2023 Shalaby et al. THIS IS AN OPEN ACCESS ARTICLE DISTRIBUTED UNDER THE CREATIVE COMMONS ATTRIBUTION LICENSE | PUBLISHED BY KNOWLEDGE E

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Phacoemulsification after Tube Shunts; Shalaby et al

INTRODUCTION

Cataract surgery in patients with preexisting
glaucoma or glaucoma surgery is challenging
considering the potential impairment of
postoperative intraocular pressure (IOP) control.
The development of cataract after glaucoma
surgery is not uncommon.[1] It has been suggested
that intraocular inflammation during and after
cataract surgery may result in scarring and fibrosis
of the filtering trabeculectomy blebs.[2] Similarly,
the inflammatory cells and mediators may cause
fibrosis around the shunt reservoir.[3] However,
there is no definite evidence supporting this
theory. Several studies have investigated the
effect of cataract surgery on trabeculectomy
blebs. There have been mixed results on the bleb
survival. While some studies showed increased
failure of trabeculectomy and IOP elevation,[4−−7]
others reported no effect.[8−−10] The literature on
the effect of cataract extraction in eyes with prior
tube shunts is limited.[3, 11, 12]

Prior studies showed lack of change in IOP
and medications number in functioning tubes
following phacoemulsification; however, they had
a limited sample size, variable follow-up duration,
and heterogenous type of glaucoma.[3, 11, 12] The
study aimed to investigate the survival of tube
shunts after phacoemulsification in patients with
primary open-angle glaucoma (POAG).

METHODS

This single-center retrospective case series was
performed at a tertiary eye care center. The
study protocol was reviewed and approved by the
Institutional Review Board of Wills Eye Hospital,
Philadelphia, PA, United States; and the approval
number was [19-857]. The study was conducted in
accordance with the Health Insurance Portability
and Accountability Act regulations. The study
protocol adhered to the tenets of the Declaration
of Helsinki and the guidelines for human studies.
As this was a retrospective study with de-identified
data, informed consent was not required. The
medical records of consecutive patients diagnosed
with POAG who were treated with tube shunts
including the Ahmed glaucoma valve (AGV; New
World Medical Inc., Rancho Cucamonga, CA, USA)
or the Baerveldt glaucoma implant (BGI; Advanced
Medical Optics, Santa Ana, CA, USA) followed by

phacoemulsification between 2008 and 2018 were
reviewed.

Patients aged 18 years or older who had
undergone successful tube shunt surgery for
POAG with IOP ≤ 21 mmHg, with or without
medications, followed by phacoemulsification
were included. Exclusion criteria were angle
closure, neovascular, or inflammatory glaucoma,
cataract extraction by any technique other
than phacoemulsification, phacoemulsification
combined with any glaucoma surgery, or a follow-
up of less than two years after phacoemulsification.
In patients with both eyes meeting the inclusion
criteria, only the first eye was included.

Visits at baseline, postoperative day 1, week
1, months 1, 3, 6, 12, 18, and 24 after the
cataract surgery were reviewed. Demographic
data such as age and sex, and medical and
surgical history were collected. Preoperative
clinical data included best-corrected visual acuity
(BCVA), IOP, topical glaucoma medications, and
cup/disc ratio (CDR) at three consecutive visits
prior to phacoemulsification. Postoperative data
included BCVA, IOP, glaucoma medications,
CDR, postoperative complications, and need for
additional glaucoma surgery.

The primary outcome measure was the
cumulative rate of surgical failure at 24 months.
Surgical failure was defined as IOP > 21 mmHg
with medications at two consecutive visits,
progression to no light perception (NLP) vision,
and glaucoma reoperation including second
tube shunts, cyclophotocoagulation, or removal
of the existing tube shunt. Changes in VA, IOP,
glaucoma medications, and CDR at month 24 were
compared to baseline. Additionally, analyses of
surgical failure defined as IOP >15 and >18 mmHg
were performed.

Statistical Analysis

Statistical analyses were performed using the SPSS
software version 27.0 (IBM Analytics, Chicago, IL,
USA). Snellen VA measurements were converted
to logarithm of the minimum angle of resolution
(logMAR) equivalents for the purpose of data
analysis. Continuous variables were presented as
mean ± standard deviation. Proportions (%) were
used to describe categorical variables. Paired
sample t-tests were used to compare continuous
variables within the same group. P-values <

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Phacoemulsification after Tube Shunts; Shalaby et al

0.05 were considered as significant. Kaplan–Meier
survival analysis with log-rank tests were used to
assess the survival.

RESULTS

Twenty-seven eyes of 27 patients were included
in this study (16 AGV and 11 BGI). Baseline patient
characteristics are shown in Table 1. The mean
age was 64.2 ± 10.8 years, and 16 (59.3%)
patients were females. All patients had moderate
to severe glaucoma. Six patients (22.2%) had prior
trabeculectomy before the tube shunt surgery.
The mean LogMAR VA, IOP, and number of
glaucoma medications were 0.94 ± 0.92, 16.0
± 4.7 mmHg, and 2.4 ± 1.5, respectively. The
average interval between tube shunt surgery and
phacoemulsification was 28.8 ± 25.0 months.

At month 24, a total of four (14.8%) eyes met
the failure criteria. Failure occurred at 19.3 ±
3.8 months after cataract extraction. Reasons for
failure were high IOP in two (50.0%) eyes and
glaucoma reoperation in two (50.0%) others. No
eye progressed to NLP vision. Higher failure rate
was observed with the surgical success defined
as IOP <18 and <15 mmHg (18.5% and 48.5%,
respectively). The rate, reasons, and time to failure
with the three failure criteria are shown in Table
2. Kaplan–Meier survival analysis showing the
cumulative rate of surgical failure at 24 months
using the three failure criteria is displayed in Figure
1.

Visual acuity improved after surgery and the
difference with baseline was statistically significant
at month six, with an improvement in logMAR VA of
0.41 ± 0.54 units (P = 0.001), but not at month 24
(0.11 ± 0.67-unit improvement, P = 0.430). No eyes
progressed to NLP vision.

Baseline and follow-up IOPs are presented in
Figure 2. Patients who met the failure criteria
due to reoperation for glaucoma implant removal
or progression to NLP vision were censored
in statistical analysis of the follow-up visits. At
postoperative day one visit, IOP was higher
compared to baseline (18.1 ± 6.2 mmHg vs 16.0 ±
4.7 mmHg, P = 0.053). Then, a tendency for lower
IOP as compared to baseline was observed at all
follow-up visits, but not statistically significant (P >
0.05), except in the third month at which IOP was
significantly lower compared to baseline (13.0 ± 3.7
mmHg vs 16.0 ± 4.7 mmHg, P = 0.011). At month 24,

the IOP was lower by 1.6 ± 5.1 mmHg compared to
baseline (P = 0.131).

Figure 3 shows the number of glaucoma
medications at baseline and follow-up. A
decremental trend for the number of glaucoma
medications was observed at all time points;
however, it was statistically significant at
postoperative months 6 and 12 compared to
baseline (P = 0.02 and P = 0.016, respectively).
At month 24, the mean number of medications
was 0.3 ± 1.5 lower compared to the baseline (P =
0.302).

Hyphema (1 [3.7%]), IOP spikes (IOP elevation
≥ 10 mmHg from the baseline) (1 [3.7%]), and
inflammatory reaction (>+1 cells in the anterior
chamber) (14 [51.9%]) were the early postoperative
complications; all resolved with conservative
management. No eyes developed persistent
corneal edema. During the follow-up period, one
eye (3.7%) required tube revision and two (7.4%)
eyes received second tube shunt.

DISCUSSION

Our study shows that the mean IOP and number
of glaucoma medications remained stable for
two years following cataract extraction in POAG
patients with a functional tube shunt. The rate of
surgical failure was 14.8%, 18.5%, and 48.5% at IOPs
of >21, <18, and <15 mmHg, respectively. While the
effect of cataract surgery on the trabeculectomy
function has been heavily studied,[4–10] there
are limited studies on the tube shunts, and
all have included various forms of open-angle
glaucoma.[3, 11, 12]

Gujral et al[12] retrospectively investigated the
outcomes of phacoemulsification in eyes with
functioning AGVs. The study included 23 eyes of
19 patients with an average follow-up of 1.6 ±
0.6 years after the cataract surgery. Similar to our
study, the mean IOP and number of medications
did not change after phacoemulsification (P >
0.05 for both). However, the follow-up in our
study was longer. The pattern of postoperative
IOP change was similar to our study; increased
from 14.5 ± 3 mmHg (preoperative) to 19.2 ±
6.3 mmHg on postoperative day one, declined
at month one, and remained stable afterward.
The surgical failure defined as IOP >21 mmHg
was observed in two (9%) eyes and one of
them (4.0%) underwent second tube shunt. These

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Phacoemulsification after Tube Shunts; Shalaby et al

Table 1. Baseline Characteristics of Patients with Phacoemulsification and Prior Tube Shunt Surgery.

Number of eyes 27

Number of patients 27

Age, yr 64.2 ± 10.8
Sex, Females: N (%) 16 (59.3)

Surgical eye, Right: N (%) 16 (59.3)

Baseline visual acuity: LogMAR 0.94 ± 0.92
Baseline intraocular pressure: mmHg 16.0 ± 4.7
Baseline medications number 2.4 ± 1.5
Baseline cup/disc ratio 0.7 ± 0.2
Glaucoma severity: N (%)

Moderate 11 (40.7)

Severe 16 (59.3)

Glaucoma intervention prior to tube shunt surgery

None 13 (48.1)

Selective laser trabeculoplasty 8 (29.6)

Trabeculectomy 6 (22.2)

Duration between tube shunt surgery and phacoemulsification:
Months

28.8 ± 25.0

Table 2. Month 24 failure in patients with phacoemulsification and prior tube shunt surgery.

Failure criteria 1: IOP > 21 mmHg
Failure: N (%) 4 (14.8)

Reasons of failure: N (%)

IOP > 21 mmHg 2 (50.0)
Reoperation for glaucoma 2 (50.0)

Progression to NLP 0 (0.0)

Time to failure: Months 19.3 ± 3.8
Failure criteria 2: IOP > 18 mmHg
Month 24 failure: N (%) 5 (18.5)

Reasons of failure: N (%)

IOP > 18 mmHg 3 (60.0)
Reoperation for glaucoma 2 (40.0)

Time to failure: Months 17.8 ± 7.6
Failure criteria 3: IOP > 15 mmHg
Month 24 failure: N (%) 13 (48.1)

Reasons of failure: N (%)

IOP > 15 mmHg 11 (84.6)
Reoperation for glaucoma 2 (15.4)

Time to failure: Months 12.6 ± 7.2

IOP, intraocular pressure; NlP, no light perception

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Phacoemulsification after Tube Shunts; Shalaby et al

Figure 1. Kaplan–Meier Survival Plot of cumulative probability of surgical failure in patients with phacoemulsification and prior
tube shunt surgery. Surgical failure was defined as intraocular pressure >21 mmHg (1A), >18 mmHg (1B), or >15 mmHg (1C).

Figure 2. Intraocular pressure changes over time in patients with phacoemulsification and prior tube shunt surgery. Intraocular
pressure remained stable through two years following phacoemulsification. Significant reduction was observed at month three (P
= 0.011).

Figure 3. Medication number changes over time in patients with phacoemulsification and prior tube shunt surgery. Medication
number remained stable through two years following phacoemulsification. Significant reduction was observed at month six (P =
0.020) and month 12 (P = 0.016).

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Phacoemulsification after Tube Shunts; Shalaby et al

findings were comparable to our failure (14.8%)
and reoperation (7.4%) rates. On the other hand,
more eyes experienced IOP spikes at day one
postoperatively (17.0%) compared to ours (3.7%).

Erie et al[3] retrospectively studied the effects of
phacoemulsification on nine eyes of eight patients
with a functioning BGI with an average follow-
up of 21.0 ± 3.0 months. The mean IOP and
number of medications did not change significantly
at the last follow-up visit (P = 0.830 and P =
0.170, respectively). Only one eye required second
glaucoma surgery.

In another retrospective study, 11 eyes of 11
patients with double plate Molteno shunt (8),
single plate Molteno shubt (2), or BGI (1) were
followed for 21.0 ± 27.0 months following cataract
surgery.[11] Phacoemulsification was performed in
eight eyes and extracapsular cataract extraction
was done in three eyes. No significant difference
was observed between the mean IOP and the
number of medications before and after cataract
extraction (P = 0.850 and P = 0.440, respectively).
Three eyes had IOP >21 mmHg and only one of
them required glaucoma surgery.

Although VA improved in the first six months,
the vision was not statistically different from
baseline at month 24. This is consistent with
prior studies, although in some studies it was
attributed to corneal edema.[11, 12] Corneal edema
was not observed in our study. Posterior capsule
opacification could be a potential cause for the lack
of change in vision after cataract extraction.

The high IOP at day one may be related to
the postoperative period IOP spikes following
cataract surgery due to viscoelastic agents.[13, 14]
The IOP decline afterward could be because of
the IOP-lowering effect of phacoemulsification in
glaucomatous eyes.[15, 16] The mechanism is not
clear, but may be related to widening of the anterior
chamber angle, decreased aqueous production by
the ciliary body due to capsular bag contraction,
or increased aqueous outflow due to trabecular
meshwork stretching.[15–17]

The results of our study are in line with
other studies on IOP profile following cataract
extraction in patients with a functional tube, but the
results on trabeculectomy are controversial. Some
studies showed that phacoemulsification increased
the surgical failure of trabeculectomy,[4–7] and
others found no effect on bleb survival.[8–10] The
mechanisms of IOP elevation following cataract

surgery in those with a functional filtering surgery
(trabeculectomy or tube shunts) seems to be
similar. Inflammatory cells and cytokines released
following cataract surgery may cause scarring of
the filtering bleb.[2, 11]

The average duration between tube shunt
surgery and phacoemulsification in this study was
variable (28.8 ± 25.0 months). It is known that
the time interval between the two surgeries may
have prognostic ramifications. It is recommended
to postpone the cataract surgery following filtering
surgery as long as possible, without compromising
patient’s quality of life. A six-month gap between
filtering surgery and the subsequent cataract
extraction increases the chances of bleb survival.[18]

The patients in our study had
phacoemulsification 28.8 months after shunt
surgery and were followed for 24 months (about
five years after shunt surgery). The failure rate
in these patients was comparable with the rate
reported in Ahmed Baerveldt Comparison (ABC)
and Ahmed versus Baerveldt (AVB) studies.[19, 20]
These findings confirm that phacoemulsification,
at least, had no negative impact on the survival of
tube shunts. However, such comparisons cannot
conclude that phacoemulsification may augment
the IOP-lowering effect of tube shunts, giving the
different follow-up duration and the inclusion of
secondary and refractory glaucoma types in the
ABC and AVB studies.[19, 20]

Our study has several limitations. There were
no preset criteria for the addition of medications
or preforming another surgery and has been at
the discretions of surgeons. This is the universal
issue with all retrospective studies. Additionally,
the sample size was small as only POAG patients
with a complete two-year follow-up were included.
The follow-up period in our study was longer than
prior studies and contrary to them we included
only one eye of each patient and only POAG
cases. Compared to all prior studies we had the
largest sample size (27 vs 9, 11, and 23 eyes), and
all patients were followed-up for at least for 24
months.[3, 11, 12] Furthermore, both valved (AGV) and
non-valved (BGI) tubes were included in this study
which makes the results closer to the real-world
practice.[19, 20]

In summary, the current study showed that
POAG patients with functioning tube shunts can
maintain IOP control after phacoemulsification,
suggesting that cataract surgery may not have a
negative impact on the survival of tube shunts.

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Phacoemulsification after Tube Shunts; Shalaby et al

Financial Support and Sponsorship

None.

Conflicts of Interest

None.

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