Open Journal of Ophthalmology, 2012, 2, 14-20
http://dx.doi.org/10.4236/ojoph.2012.22004 Published Online May 2012 (http://www.SciRP.org/journal/ojoph)
Effect of Phacoemulsification on Intraocular Pressure
Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
Samir Aziz1*, Nicky Spiers2, Jeffrey Jay3
1Moorfields Eye Hospital NHS Foundation Trust, London, England; 2Tennent Institute of Ophthalmology, Gartneval General Hospi-
tal, Glasgow, Scotland; 3University of Leicester, Leicester, England.
Received December 26th, 2011; revised January 19th, 2012; accepted February 9th, 2012
ABSTRACT
Purpose: To analyse the effect of phacoemulsification on the control of intraocular pressure in primary open angle
glaucoma in patients having phacoemulsification after previous trabeculectomy and compare them with a control group
who had trabeculectomy alone. Patients and Methods: Twenty one patients (one eye from each) who had phacoemul-
sification subsequent to trabeculectomy were identified, and compared with 41 controls. Intraocular pressure, bleb ap-
pearance, glaucoma medications, iris manipulation and complications were recorded. Each patient was followed for full
12 months. Failure of control was defined as follows: 1) intraocular pressure >21 mm Hg on medication, or 2) a greater
number of glaucoma medications than before phacoemulsification. Results: The post operative change in intraocular
pressure in the case group at 12 months was much less than that in the control (p = 0.001). The mean intraocular pres-
sure had changed from 15.3 mm Hg to 14.7 mm Hg. The control group showed an average intraocular pressure reduc-
tion of 6 mm Hg at the last visit (p > 0.001). In phacoemulsification group, 19% required 1 or 2 glaucoma medications
at one year follow-up vs 19.5% in the control group. In phacoemulsification group, 9.5% showed flattening of a previ-
ously formed bleb at the last visit (P < 0.001), compared with 9.7% of controls. Conclusions: The stability of glaucoma
control in the first year after phacoemulsification in previously filtered eyes with primary open angle glaucoma is com-
parable to that of the natural course after trabeculectomy. The study is limited by the small number of cases available.
Keywords: Phacoemulsification; Trabeculectomy; Cataract; Glaucoma
1. Introduction
Glaucoma and cataract often coexist in the same eye [1,2]
not only because they both occur in the elderly popula-
tion, [3,4] but also because antiglaucoma medications
may contribute to the formation and development of
cataract [1]. In addition, glaucoma filtering surgery may
accelerate cataract formation [5,6], possibly in 14% -
40% of patients [7,8].
One of the accepted surgical options in patients with
severe glaucoma and coexisting cataract is first to control
the intraocular pressure (IOP) with trabeculectomy and
then extract the cataract several months later [9]. There-
fore, the management of visually significant cataract in a
glaucoma patient who has had a previous trabeculectomy
is a common clinical problem [1,10,11].
Several studies have examined the effect of phacoe-
mulsification (PE) [1,10,11,12-14] and extracapsular
cataract extraction (ECCE) [1,10,11,12-13] on interme-
diate and long-term IOP control after trabeculectomy,
with conflicting results. When cataract surgery is per-
formed in filtered eyes there is a risk of early postopera-
tive increase in IOP and loss of long-term IOP control [3,
6,14-18]. Others have found that IOP control can be re-
tained after cataract extraction by increasing antiglau-
coma medications [10], while some report that increased
IOP is not observed in patients with previous filtering
surgery and that none of their patients required additional
antiglaucoma medications [19].
More specifically, the effect of ECCE technique on fil-
tering blebs has been investigated [10,12,13]. Ten to
thirty-eight percent of eyes with previous trabeculectomy
require additional medication or further glaucoma sur-
gery to maintain IOP after ECCE with IOL implantation
[10,13,14]. Phacoemulsification seems to have fewer
adverse effects on the postoperative IOP control than
ECCE; however, bleb dysfunction may still occur in the
postoperative period [10,13,15,18,20].
In this retrospective study we quantitatively analyze
*Corresponding author.

Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
15
the effect of PE on the control of IOP in POAG in pa-
tients having PE after previous trabeculectomy (trabe-
culectomy-phacoemulsification group). In order to allow
for any intrinsic instability of IOP control after trabe-
culectomy undisturbed by PE, we compare them with a
control group who underwent trabeculectomy alone (tra-
beculectomy group).
2. Patients and Methods
A retrospective and consecutive case note review was
performed on 21 Caucasian patients who had trabeculec-
tomy for uncontrolled POAG followed by PE at Gartna-
vel General Hospital in Glasgow, UK. A trabeculectomy-
phacoemulsification (TP) group was compared with the
control group (41 consecutive Caucasian patients) who
had trabeculectomy (T) alone for uncontrolled POAG
without cataract surgery at the same hospital. Patients
with other types of glaucoma or who had received anti-
metabolites during or after the trabeculectomy were ex-
cluded. Each patient was followed for full 12 months
after PE and trabeculectomy respectively. Only one eye
of each patient was included.
The following data were obtained for each patient in
both groups: gender, age, bleb appearance, number and
type of glaucoma medications, previous ocular surgeries,
time elapsed between T and PE, IOP preceding surgery,
and IOP at 1 day, 1 week, 3, 6, 9, and 12 months after
surgery, intraoperative iris manipulation (posterior sy-
nechialysis, stretching, sphincterotomies and iridectomy),
intraoperative and postoperative complications, postop-
erative medications administered, and the dates when
additional glaucoma medications were added. At the fi-
nal visit, the number of glaucoma medications, IOP and
bleb appearance were documented.
In the TP group, phacoemulsification was performed
in 21 patients by several experienced surgeons, using a
3.2 mm superior clear-corneal incision. A foldable poste-
rior chamber acrylic, hydrophobic lens (IOL) was in-
serted in the capsular bag. Small pupils were surgically
enlarged by iris manipulation. In no case was an anterior
chamber IOL inserted.
In all patients of both groups, same technique of T was
performed by one surgeon (J.J.); using a fornix based
conjunctival flap, however less than 5 were done by ex-
perienced surgeons who followed the same technique
under his direct supervision. Post operative medications
included topical corticosteroid and antibiotic drops used
4 times daily for 4 weeks in both groups. Cycloplegic
drops were administered twice daily for 2 weeks after T.
Intraocular pressure, bleb appearance, and number of
glaucoma medications were compared between the 2
groups.
For the purposes of the study and for comparison with
other studies, we used two criteria to define failure: 1) an
IOP greater than 21 mm Hg on medication, or 2) a
greater number of glaucoma medications than before PE.
Patients who had received antifibrotics were excluded.
Outcomes were compared between the two groups us-
ing the Mann-Whitney U test, Chi square and Student’s
t-test where appropriate. Random effects models with
normal errors were fitted to the IOP profiles for months 1,
3, 6, 9 and 12 using Proc Mixed in SAS. Because of great
variability in pressures in the first month, measures taken
prior to one month post-operatively were not modeled.
Models were compared using the Likelihood Ratio Test.
Differences were considered significant at the 5% level.
3. Results
The patient’s characteristics are shown in Table 1. There
is a difference between the mean ages in the 2 groups.
The mean time between T and PE was 52.6 months (SD
22.6, range 16 - 93). In the TP group, 9.5% (n = 2, Table
2) showed flattening of a previously formed bleb at one
year follow-up (P < 0.03). The trabeculectomy group was
similar (9.7%, n = 4).
The mean IOP of the case group one year after PE had
fallen very slightly from 15.3 mm Hg (SD 4.5, range 10 -
25) preoperatively to 14.7 mm Hg (SD 3.5, range 10 -
22). However, one patient had an IOP of 22 mm Hg at
the latest examination. At the last visit, patients who re-
quired antiglaucoma medications after PE had a mean
IOP before PE of 21.5 mm Hg (SD 1.7, range 20 - 23),
which was higher than those controlled without glau-
coma medication 14 mm Hg (SD 3.9, range 10 - 25).
The post operative change in IOP in the TP group at
12 months was much less than the change in IOP fol-
lowing trabeculectomy (Median change 0 versus –6 p =
0.001; Mann-Whitney U test).
The control group showed an average IOP reduction of
6 mm Hg in the last visit (p > 0.001). There was no evi-
dence that the difference in mean IOP between the
groups varied with time, or that there was any change in
between subjects variation in pressure. The best fitting
model had parallel quadratic mean profiles for the case
and control groups, with an increase in mean IOP over
time (Figures 1 and 2). Figure 1 also confirms that the
curves for long term change in IOP are similar in both
groups.
The estimated mean IOP profile shown in Figure 1 is
higher for cases than for controls, but this difference was
not significant (mean difference 0.85 mm Hg; 95% CI
–0.84 to 2.54).
Two outliers in the control group were not well fitted

Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
16
Table 1. Characteristics of patients in the two groups.
Trabeculectomy
Trabeculectomy-
Phacoemulsification P-value Test
Diagnosis POAG 41 21
Age (years) Mean (range) 74 (57 - 87) 78 (61 - 91) 0.01 Unpaired t-test
Sex 0.24 Chi square
Male 20 7
Female 21 14
IOP (mean) Baseline 15.3 (10 - 25) 14.7 (10 - 22)
Postoperative 21 (15 - 31)* 15 (7 - 26)†
Elapsed time between glaucoma and
cataract surgeries (months) Mean (range) N/A 52.6 (16 - 93)
Iris manipulation 5
POAG: primary open angle glaucoma; IOP: intraocular pressure; *: 12 months post trabeculectomy; †: 12 months post phacoemulsification.
by the model. ID 121 had unusually high IOP throughout.
ID 140 had an unusual increase in IOP from 6 at month 1
to 22 at month 3 and persisted at that level. When the
final model was refitted with these two subjects included
there was a slight increase in the difference in means
between groups (Table 3), but the difference in mean
profiles between the groups did not reach significance in
either model.
129631
months postoperative
18.00
17.00
16.00
15.00
14.00
13.00
12.00
IOP (mmHg)
case
control
group
There was one missing value at month 9 in the case
group. The other values for this individual were included
in the analysis, and the missing value is not considered to
have any bearing on the conclusions.
In the PE group, 4 patients (19%) required 1 or 2
glaucoma medications at one year (Table 2). One had
high IOP preoperatively; the other had required treatment
prior to PE. In the trabeculectomy group eight patients
(19.5%) used glaucoma medication one year after T, and
5 of them used a single medication. Iris manipulation
was required in 5 patients (3 posterior synechialysis, 1
stretching, and 1 sphincterotomy) to disrupt posterior
synechiae during cataract surgery in the PE group; three
of these needed glaucoma medications in the first month.
However, IOP was controlled thereafter without lowering
drops.
Figure 1. Predicted mean intraocular pressure from final
model, with 95% confidence intervals.
In the TP group there were postoperative IOP spikes in
8 eyes (38%) on the first day and in a further 2 eyes in
the first week. In the same group, endophthalmitis de-
veloped in one eye one week postoperatively, it was
successfully treated with intravitreal amikacin, it retained
a VA (visual acuity) of 6/60 in the last visit.
4. Discussions
Figure 2. Real values of intraocular pressure in both
groups. Cataract extraction in eyes functioning filtering with a

Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
17
Table 2. Intraocular pressure, number of medications and bleb appearance in the case group.
IOP (mm Hg) Number of me d ications
Case Preop Last visit Preop Last visit Bleb appearance
1 14 16 0 0 NC
2 14 12 0 0 NC
3 19 12 0 0 NC
4 10 12 0 0 NC
5 14 13 0 0 NC
6 13 18 0 0 NC
7 12 19 0 0 NC
8 11 18 0 0 NC
9 20 14 1 1 NC
10 14 12 0 0 NC
11 13 14 0 0 NC
12 20 10 1 1 Flattened
13 23 22 0 1 Flattened
14 14 12 0 0 NC
15 10 19 0 0 NC
16 15 17 0 0 NC
17 10 10 0 0 NC
18 25 12 0 0 NC
19 23 12 0 2 NC
20 14 15 0 0 NC
21 14 20 0 0 NC
IOP: intraocular pressure; NC: no change.
Table 3. Mean difference in intra ocular pressure (IOP) profiles from random effects model.
Model N Difference in mean IOP (Case-control) LCL UCL P-value for difference
1 62 0.77 –0.99 2.53 0.39
2 (Outliers excluded) 60 1.05 −0.54 2.64 0.20
N: number; IOP: intraocular pressure; LCL: lower 95% confidence limit; UCL: upper 95% confidence limit.
bleb is considered to be a risk [17]. Small incision cata-
ract surgery is the technique of choice in this group [1,
16], because there is less conjunctival dissection and in-
flammation [1]. Several studies report that PE has a
minimal effect on the long-term mean IOP after T [2,10,
12]. However, PE may jeopardize a previously function-
ing filtering bleb and result in increase in IOP [4,11,
15,18].
This study is an attempt to isolate the IOP as one spe-
cific aspect of glaucoma and to determine if that single
factor is affected by later PE.
We did not include visual field since it might be in-
fluenced by lens opacities [21]. We showed that the IOP
in the TP group at up to one year after PE was not sig-
nificantly altered. Other studies (Table 4) have shown
variable results and in some, either no significant differ-
ence or a decrease in IOP was detected [10,11,14,22,23].
Park et al. [14] used a control group that had T alone and
showed that PE seemed to have no effect on IOP control
after PE. However, unlike our study their case-control
study was not limited to cases of POAG. Furthermore,
antimetabolites had been used which might have affected

Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
18
Table 4. Summary of studies on the effects of phacoemulsification in eyes with filtering blebs.
Study No. Follow-up (m)Success (%)Definition of success
Seah et al. [13] 6 13.6 67 IOP < 19 mm Hg with no additional surgery and no additional
medications
Chen et al. [10] 57 17.6 74 No additional medications, bleb needling, or glaucoma surgery
Park et al. [14] 40 20.1 80 (3 yrs) No greater number of medications: IOP ≤ 21 mm Hg or >20% re-
duction on 2 consecutive visits compared with pretrabeculectomy
Manoj et al. [11] 21 15.1 100 IOP < 18 mm Hg and within the target pressure
Crichton & Kirker [15] 69 23.2 77 No additional surgery and no additional medications compared
with pre cataract
Rebolleda & Munoz-Negrete. [17] 49 19.5 67.4 No glaucoma medications, surgery, or bleb needling to control IOP
Ehrnrooth et al. [4] 46 25.3 69.5 IOP ≤ 21 mm Hg with no additional surgery and no or single
topical medications
Present study 21 12 85.7 IOP ≤ 21 mm Hg with no additional surgery and no additional
medications
the outcome, in contrast to our study where patients who
had received antimetabolites were excluded in order to
reduce case mix and subsequently bias.
On the other hand, the most frequent conclusion is that
there is an increase in IOP after PE [1,10,12,15,17,19,
23-25].
Our aim was to describe the changes provoked by a
second surgical procedure. When the time between tra-
beculectomy and PE was greater than 1 year the interval
between surgeries had no effect on bleb failures, IOP, or
medication changes [17]. In our study cohort, the time
between T and PE is rather long, since we feel that most
of them do not need cataract surgery earlier than that.
The success rate after 1 year in our TP group was
85.7%, Table 4 shows the success rate reported in the
literature. The rate varies between 67% and 100% but the
definition of success is slightly different in the different
studies and not all included a control group. Most of the
failures occurred between 6 and 24 months after PE, in-
dicating that the effect on bleb filtration is a delayed re-
sponse [26].
There is a recognized trend for a late rise in IOP after
T [18]; therefore PE might not be the only possible ad-
verse influence on IOP [27]. A decrease in IOP over time
after successful T has been reported [28]. In our study,
allowing for the possible change in long term IOP control
after T, PE seemed to have no additional effect on IOP
control.
The use of glaucoma medications is similar in the case
(19%) and control (19.5%) groups. This figure matches
one other study (20%) [15]. But most authors report
more frequent use of medications [10,14]; (22%) [29],
(34.7%) [17], (49.4%) [2], (41%) [4]. In our study, the
number of glaucoma medications did not change much in
the TP group during the course of the study, whereas in
the T group 9% required additional pressure-lowering
medications.
Evaluation of bleb morphology in retrospective studies
without standardized criteria is difficult and very subjec-
tive. We found flattening of the bleb in 9.5% and 9.7% in
the case and control groups respectively. Others have
found this to be more frequent (77.6%) [17], (18%) [10].
It is likely that the inflammatory response elicited by
surgery induces subconjunctival scarring [20]. This could
explain the flattening of the filtering bleb and subsequent
IOP increase that may occur even after the relatively
atraumatic PE procedure [10,12,13,17,29]. The presence
of a functional filtering bleb before surgery does not
guarantee long-term IOP control after PE [17].
In our study, PE was performed at least 16 months af-
ter T, and under these conditions, the time between T and
PE did not seem to influence failure, glaucoma medica-
tion use or IOP changes. Some authors believe that the
filtering bleb needs sufficient time (>5 months) [14], (≥6
months) [24], or (≥1 year) [13] to develop properly since
the inflammation associated with cataract surgery may
induce bleb failure [10]. However, others showed no
association between IOP control and the timing of cata-
ract surgery [14].
Iris manipulation in our study seemed not to be associ-
ated with poor IOP control, bleb failure or need for addi-
tional medications. Similar findings were reported by
others good IOP control [18,27], no bleb failure [10,13]
no additional medications [15,16,24]. Other studies did,
however, find an association with bleb failure [24,27].
Severe postoperative complications after PE were rare
in our study. Early postoperative IOP spikes are fre-
quently observed after cataract surgery in glaucomatous
eyes. We observed an IOP spike of ≥8 mm Hg in 4 eyes
(19%) 1 day after PE. A prospective study by Rebolleda

Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously
Treated by Trabeculectomy: A Case-Control Study
19
& Muñoz-Negrete [17] found a similar rate (18.4%, IOP
> 10 mm Hg). Others have reported higher (57%) [30],
(50%) [14], (37%) [14], or lower rates (6.3% ≥ 30 mm
Hg) [24].
Intraocular pressure fluctuations during the first post-
operative months after routine cataract extraction are
well known [11].
Our study used only eyes with POAG, which carries
the best prognosis for T. Therefore, our favorable obser-
vations may not be extrapolated to other types of glau-
coma where a successful drainage fistula might more
readily be compromised by subsequent PE.
There is 4 year age difference between both groups;
however we do not feel that this is a source of clinically
meaningful bias. Our study has the benefit of a control
group which enables us to make allowance for the
change in IOP which might occur after T. Another
strength is the analysis of repeated measurements of IOP
during the year which allowed a detailed comparison of
the behavior of the IOP in the two groups.
Limitations of this study are its retrospective nature
and the lack of statistical significance; this may be attrib-
utable to the relatively small sample size.
We conclude that the stability of glaucoma control in
the first year after PE in previously filtered eyes with
POAG is comparable to that of the natural course of T.
A future, large, prospective and controlled study could
provide more reliable data about the effect of PE on the
function of a previous fistulising operation.
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