Pseudoexfoliation syndrome (PXF) is an age-related disorder of
extracellular matrix which is commonly associated with glaucoma and cataract.1 It appears to be a common disorder in elderly in Upper Egypt.2 Compared to primary open angle glaucoma, glaucoma associated with PXF
tends to have more severe and a rapidly progressive course, higher intraocular
pressure (IOP) and poorer response to medications.3 Therefore, close
monitoring and control of IOP in PXF; especially in eyes with ocular
hypertension or pseudoexfoliative glaucoma (PXG), is an important issue.
Several studies have noted a decrease in IOP
following cataract surgery, either in eyes
with PXF 4 or eyes without PXF.5, 6 Thinking of cataract surgery
as an option for reduction of the risk of developing ocular hypertension or PXG
in eyes with PXF; especially in developing countries where close IOP monitoring
is a difficult issue, is now emerging. The aim of this study was to evaluate
the effect of cataract surgery on IOP in eyes with PXF in Egyptian population.
Patients and methods:
This study is a prospective, non-randomized, observational,
age-matched, comparative clinical study. Approval was obtained from the Medical
Research Ethics Committee of the institution that adhered to the tenets of the
Declaration of Helsinki.
The study was performed in Department of Ophthalmology at Assiut
University Hospital in the period from January 2015 to December 2016.
Patients who met the eligibility criteria were enrolled in one of
two groups: those with PXF (n=32 eyes) and those without PXF (n=32 eyes).
criteria were: visually significant cataract, age 50 years or above. The
diagnosis of PXF was based on the presence of exfoliative material on the
anterior lens capsule or pupillary border with moth eaten appearance of the
pupil under slit-lamp biomicroscopy before and after pupil dilation.
Exclusion criteria were:
eyes with established glaucoma, secondary cataract, subluxated lenses, corneal abnormalities
that may interfere with reliable applanation tonometry, previous ocular trauma
or surgery, other ocular diseases that may affect IOP (e.g. retinal detachment,
evidence of previous attacks of uveitis, diabetic retinopathy) or visual
function (e.g. macular degeneration) and intraoperative complications during
cataract surgery that may affect the postoperative IOP e.g. posterior capsular
rupture with vitreous loss.
Two techniques were used for cataract
extraction either PECCE or phacoemulsification; the choice between the two
techniques was based on degree of
nuclear hardness. In each group, 22 eyes underwent PECCE and 10 eyes underwent
phacoemulsification. Surgery was performed by the four surgeon involved in the study using
the same surgical technique.
PECCE was done by 10-12mm superior limbal incision, capsulotomy, manual nucleus expression, irrigation/aspiration of
remaining cortex, placement of a single piece rigid PMMA (Poly Methyl Metha Acrylate) PCIOL (Posterior chamber intraocular lens) (6.5mm optic) into the capsular bag and closure of the limbal
wound by four to five interrupted 10-0 nylon sutures.
was done through 2.5-3mm clear corneal incision, capsulorhexsis,
phacoemulsification of the nucleus, cortical aspiration and foldable acrylic PC
IOL was implanted in the capsular bag.
acuity, IOP and other ocular findings were recorded preoperatively and
postoperatively at (one day, one week, one month and three months) in a
standardized data collection sheet. Visual acuity was measured by Snellen chart
and converted into log MAR equivalents. IOP was measured by Goldmann
entry and data analysis were done using IBM SPSS (statistical package for
social science) Statistics for Windows, Version 20.0. Normality for all study
variables was assessed using Shapiro-Wilks analysis. Mann-Whitney U test was
used to compare the mean IOP, mean IOP change, mean IOP change percentile and log
MAR V/A between the two study groups and between the two surgical techniques.
The Wilcoxon signed-rank test was used to compare between preoperative and
postoperative IOP in each group. Spearman
correlation coefficients were calculated to analyze the association between
mean postoperative IOP change and preoperative IOP. Multivariate analysis model
including all eyes involved in the study; with the final reduction in IOP as a dependent
variable and preoperative IOP, the presence of PXF, age and gender as predictor
variables, was done. P value of 0.05 or
less was considered significant.
Mean patient age in PXF group was 66.5 years± 7.624 SD (range from 52 to 85
years) and in control group was
64.37 years± 6.81
SD (range 50 to 76 years); the difference between the two groups was
statistically insignificant (P = 0.244).
There were 23 males (71.9%) and 9 females (28.1%) in
PXF group, while there was 17 males (53.1%) and 15 females (46.9%) in the
control group. PXF group involved 18 right eyes
and 14 left eyes. The control group involved 21 right eyes and 11 left eyes. The difference in the proportion between
the two groups as regarding sex and laterality of the eye was insignificant
(P=0.098 for sex, P=0.304 for the laterality; Fisher’s Exact test).
1 shows the preoperative best corrected visual acuity (BCVA) and final BCVA at 3
months postoperatively in the two groups in log MAR. There was a statistically
significant improvement in mean log MAR BCVA in the two groups. The difference
in the final BCVA between the two groups was insignificant (P=0.612). The
improvement in the final BCVA was significantly greater after phacoemulsification
than after PECCE (P=0.005 in PXF group, p<0.001 in control group). Mean preoperative IOP in PXF group was 14.53±3.253mmHg (range from 10-23mmhg) and in the control group was 13.97±2.335mmHg (range from 10-19mmhg), the difference between the two groups was statistically insignificant. Postoperative mean IOP in the two groups was significantly lower than the preoperative level at all postoperative visits. Mean postoperative IOP was significantly lower in PXF groups than control groups at one month (P=0.02) and three months (P=0.048). Table 2 shows: mean preoperative and postoperative IOP in the two groups (fig.1), P value of difference between preoperative and postoperative IOP; and P value of difference in IOP between the two study groups using different surgical techniques (fig.2, fig.3). Table 3 shows mean IOP reduction and table 4 shows mean IOP reduction percentile; postoperatively at one week, one month and three months, from the preoperative IOP. The amount of IOP reduction was significantly greater in PXF group than control group at one month (P=0.014) and three months (P=0.012). The IOP reduction percentile was significantly greater in PXF group than control group at all post-operative visits. When comparing PECCE to phacoemulsification, mean postoperative IOP was significantly lower after PECCE than after phacoemulsification only in PXF group (at one week (P=0.008), at one month (P<0.001) and at three months (P=0.035) (table 5). The mean IOP reduction was significantly greater after PECCE than after phacoemulsification at one month in the two groups (P=0.009 in PXF group, P=0.0347 in control group) (table 6). IOP reduction percentile was significantly greater after PECCE at all follow-up visits in PXF group and at one month only in control group (table 7). Multivariate linear regression analysis; including all eyes involved in the study, demonstrated that preoperative IOP (P<0.001) , the presence of PXF (P=0.004) and the type of surgical technique (P=0.045) have a significant impact on the final amount of IOP reduction, while age (P=0.636) and gender (P=0.865) have insignificant impacts. There is a strong positive correlation between the preoperative IOP and the IOP reduction (using Spearman correlation coefficient). In PXF group, correlation coefficient r was 0.631 at 1 week (p<0.001), 0.542 at 1 month (p=0.001), 0.630 at 3 months (p<0.001). In control group, correlation coefficient r was 0.694 at 1 week (p<0.001), 0.602 at 1 month (p<0.001), 0.721 at 3 months (p<0.001). Discussion In this study, we found a significantly lower postoperative IOP in eyes with PXF than in eyes without PXF. When comparing the magnitude of IOP decrease in both groups, we found a significant difference between both groups at one month (P=0.014) and three months (P=0.012), but not at one week (P=0.111). We performed cataract surgery by two techniques: phacoemulsification and PECCE. Several studies compared the effect of phacoemulsification on IOP in eyes with and without PXF. Some studies found a significantly lower postoperative IOP in eyes with PXF than in those without.7-9 Other studies failed to detect any significant difference in postoperative IOP between eyes with PXF and eyes without PXF.10-12 Similarly, We found an insignificant difference between eyes with PXF and eyes without PXF after phacoemulsification as regarding postoperative IOP level, postoperative IOP reduction and postoperative IOP reduction percentile at all follow up visits; which is consistent with the finding of the last three studies. Up to our knowledge, only one study compared the effect of PECCE with PCIOL on IOP in eyes with and without PXF. Rustam et al performed a prospective age- matched study on 40 eyes with PXF and 42 eyes without PXF. The study found a significant IOP decrease at one month and three months postoperatively in both groups. However, there was insignificant difference in postoperative IOP between both groups.13 In this study, postoperative IOP was significantly lower than preoperative IOP at all follow up visits in both groups after PECCE with PCIOL. In contrast to the above study, this study found a significantly lower postoperative IOP at all follow up visits in eyes with PXF than in eyes without PXF. The exact mechanism of IOP reduction after cataract surgery is unknown, but it may be due to increase of the anterior chamber depth and widening of its angle after replacing progressively growing crystalline lens by thin PCIOL, with backward rotation of ciliary body and relief of compression on trabecular meshwork and canal of Schlemm.5 In eyes with PXF, weak zonules cause forward shift of the crystalline lens with reduction in the anterior chamber depth.1 Thus, it is thought that cataract surgery has a greater impact on deepening of the anterior chamber and widening of its angle in eyes with PXF than in eyes without. This impact could explain why cataract surgery causes greater IOP reduction in eyes with PXF than in eyes without. Güngör et al used Scheimpflug imaging system to compare the change in ACD in eyes with PXF to eyes without PXF after phacoemulsification. They found a significantly more increase in ACD in eyes with PXF than in eyes without PXF.14 Prostaglandins release after intraocular manipulation cause disruption of the blood aqueous barrier with protein leakage and elevation of IOP for several hours. This is followed by prolonged hypotony secondary to increased uveuoscleral outflow.15 Prostaglandins have two opposite effects on IOP; ocular hypertensive effect at high concentration and ocular hypotensive effect at low concentration.16 Oshika et al found that the blood ocular barrier disruption induced by cataract surgery (either phacoemulsification or PECCE) with abnormally high flare intensity persist for up to six months postoperatively.17 As the postoperative inflammation is more severe in eyes with PXF than eyes without, it is expected that its hypotensive effect is more pronounced in eyes with PXF than in eyes without.18 Shingelton et al suggested that the capsule contraction after cataract surgery exert traction the ciliary body via the zonules, which leads to aqueous hyposecretion. They supported this theory by observing that IOP was elevated by 2.2 mmHg after Neodymium:YAG capsulotomy which led to partial relief of the capsular contracting force on the ciliary body.19 Similarly, Jayne et al found a significant rise of IOP after Neodymium:YAG capsulotomy which lasted for up to 3 years.20 Jacobi et al proposed that the irrigating solutions used during cataract surgery (whose volume reaches up to 40 times the volume of the anterior chamber during PECCE and more than 200 times during phacoemulsification) have a 'rinsing' effect on the pores of the trabecular meshwork.21 Based on this theory, they developed a new technique called "trabecular aspiration" to wash the accumulated EXM and pigments in the trabecular meshwork of eyes with PXF. Combined with cataract extraction (phaco or PECCE), trabecular aspiration reduced IOP in eyes with PXG by 45% from baseline at 2 years after surgery; where as a primary therapeutic procedure, trabecular aspiration reduced IOP by 43% from baseline at 18 months postoperatively.22 Damji et al thought that lens removal eliminates iridolenticular friction and thus reduces the release of pigment from the iris and exfoliation material from the lens and iris.8 In this study, when we compared PECCE to phacoemulsification, we found that PECCE produced a greater IOP reduction than phacoemulsification; however, the difference between the two techniques was only significant at one month. Similar to our finding, Saccà et al found that PECCE reduced IOP more than phacoemulsification. They explained their finding by the greater prostaglandins release after PECCE than after phacoemulsification.23 It is known that longer corneoscleral wound of PECCE produces more irritation to the uveal tissues, leading to more release of inflammatory mediators compared to phacoemulsification.17 In this study we found that higher preoperative IOP was associated with greater postoperative IOP reduction (fig.4). Several studies reported the same observation.5, 24 We found that age and gender did not significantly affect the amount of postoperative IOP reduction. A similar finding was reported by Shingelton et al4 and Poley et al.5 The limitations of this study are: low number of eyes operated by phacoemulsification relative the number of eyes operated by PECCE, relative short period of postoperative follow-up. Our study did not evaluate the effect of cataract surgery on glaucomatous eyes. Further studies are needed to evaluate the effect of cataract surgery on IOP in eyes with PXG and to compare its effect with combined cataract surgery and trabeculectomy or staged cataract and trabeculectomy surgery. In conclusion, this study found that cataract surgery in eyes with PXF; either by PECCE or phacoemulsification, reduced IOP for up to three months postoperatively from the preoperative level. This effect can be considered as a protective or therapeutic option against development of ocular hypertension or PXG in eyes with PXF which is commonly occurred in elderly; for whom regular IOP monitoring is a difficult issue in developing countries.