Introduction: Pseudoexfoliation syndrome (PXF) is an age-related disorder ofextracellular 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 PXFtends to have more severe and a rapidly progressive course, higher intraocularpressure (IOP) and poorer response to medications.3 Therefore, closemonitoring and control of IOP in PXF; especially in eyes with ocularhypertension or pseudoexfoliative glaucoma (PXG), is an important issue. Several studies have noted a decrease in IOPfollowing cataract surgery, either in eyeswith PXF 4 or eyes without PXF.5, 6 Thinking of cataract surgeryas an option for reduction of the risk of developing ocular hypertension or PXGin eyes with PXF; especially in developing countries where close IOP monitoringis a difficult issue, is now emerging. The aim of this study was to evaluatethe 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 MedicalResearch Ethics Committee of the institution that adhered to the tenets of theDeclaration of Helsinki.The study was performed in Department of Ophthalmology at AssiutUniversity Hospital in the period from January 2015 to December 2016. Patients who met the eligibility criteria were enrolled in one oftwo groups: those with PXF (n=32 eyes) and those without PXF (n=32 eyes).Inclusioncriteria were: visually significant cataract, age 50 years or above. Thediagnosis of PXF was based on the presence of exfoliative material on theanterior lens capsule or pupillary border with moth eaten appearance of thepupil under slit-lamp biomicroscopy before and after pupil dilation. Exclusion criteria were:eyes with established glaucoma, secondary cataract, subluxated lenses, corneal abnormalitiesthat may interfere with reliable applanation tonometry, previous ocular traumaor surgery, other ocular diseases that may affect IOP (e.g.
retinal detachment,evidence of previous attacks of uveitis, diabetic retinopathy) or visualfunction (e.g. macular degeneration) and intraoperative complications duringcataract surgery that may affect the postoperative IOP e.g. posterior capsularrupture with vitreous loss.
Two techniques were used for cataractextraction either PECCE or phacoemulsification; the choice between the twotechniques was based on degree ofnuclear hardness. In each group, 22 eyes underwent PECCE and 10 eyes underwentphacoemulsification. Surgery was performed by the four surgeon involved in the study usingthe same surgical technique.
PECCE was done by 10-12mm superior limbal incision, capsulotomy, manual nucleus expression, irrigation/aspiration ofremaining 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 limbalwound by four to five interrupted 10-0 nylon sutures.Phacoemulsificationwas done through 2.
5-3mm clear corneal incision, capsulorhexsis,phacoemulsification of the nucleus, cortical aspiration and foldable acrylic PCIOL was implanted in the capsular bag.Visualacuity, IOP and other ocular findings were recorded preoperatively andpostoperatively at (one day, one week, one month and three months) in astandardized data collection sheet. Visual acuity was measured by Snellen chartand converted into log MAR equivalents. IOP was measured by Goldmannapplanation tonometry.Dataentry and data analysis were done using IBM SPSS (statistical package forsocial science) Statistics for Windows, Version 20.0.
Normality for all studyvariables was assessed using Shapiro-Wilks analysis. Mann-Whitney U test wasused to compare the mean IOP, mean IOP change, mean IOP change percentile and logMAR V/A between the two study groups and between the two surgical techniques.The Wilcoxon signed-rank test was used to compare between preoperative andpostoperative IOP in each group. Spearmancorrelation coefficients were calculated to analyze the association betweenmean postoperative IOP change and preoperative IOP.
Multivariate analysis modelincluding all eyes involved in the study; with the final reduction in IOP as a dependentvariable and preoperative IOP, the presence of PXF, age and gender as predictorvariables, was done. P value of 0.05 orless was considered significant.ResultsMean patient age in PXF group was 66.5 years± 7.624 SD (range from 52 to 85years) and in control group was64.37 years± 6.81SD (range 50 to 76 years); the difference between the two groups wasstatistically insignificant (P = 0.
244).There were 23 males (71.9%) and 9 females (28.
1%) inPXF group, while there was 17 males (53.1%) and 15 females (46.9%) in thecontrol group.
PXF group involved 18 right eyesand 14 left eyes. The control group involved 21 right eyes and 11 left eyes. The difference in the proportion betweenthe 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).Table1 shows the preoperative best corrected visual acuity (BCVA) and final BCVA at 3months postoperatively in the two groups in log MAR. There was a statisticallysignificant improvement in mean log MAR BCVA in the two groups. The differencein the final BCVA between the two groups was insignificant (P=0.
612). Theimprovement in the final BCVA was significantly greater after phacoemulsificationthan after PECCE (P=0.005 in PXF group, p<0.001 in control group).Meanpreoperative IOP in PXF group was 14.53±3.
253mmHg(range from 10-23mmhg) and in the control group was 13.97±2.335mmHg (range from10-19mmhg), the difference between the two groups was statisticallyinsignificant. Postoperativemean IOP in the two groups was significantly lower than the preoperative levelat all postoperative visits. Mean postoperative IOP was significantly lower inPXF groups than control groups at one month (P=0.02) and three months (P=0.
048).Table2 shows: mean preoperative and postoperative IOP in the two groups (fig.1), Pvalue of difference between preoperative and postoperative IOP; and P value ofdifference in IOP between the two study groups using different surgicaltechniques (fig.2, fig.
3).Table3 shows mean IOP reduction and table 4 shows mean IOP reduction percentile;postoperatively at one week, one month and three months, from the preoperativeIOP. The amount of IOP reduction was significantly greater in PXF group thancontrol group at one month (P=0.014) and three months (P=0.012).
The IOPreduction percentile was significantly greater in PXF group than control groupat all post-operative visits.Whencomparing PECCE to phacoemulsification, mean postoperative IOP wassignificantly lower after PECCE than after phacoemulsification only in PXFgroup (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 afterPECCE than after phacoemulsification at one month in the two groups (P=0.009 inPXF group, P=0.
0347 in control group) (table 6). IOP reduction percentile wassignificantly greater after PECCE at all follow-up visits in PXF group and at onemonth only in control group (table 7).Multivariatelinear regression analysis; including all eyes involved in the study, demonstratedthat preoperative IOP (P<0.001) , the presence of PXF (P=0.004) and the type of surgical technique (P=0.045) havea significant impact on the final amount of IOP reduction, while age (P=0.
636)and gender (P=0.865) have insignificant impacts.Thereis a strong positive correlation between the preoperative IOP and the IOPreduction (using Spearman correlation coefficient). In PXF group, correlationcoefficient r was 0.631 at 1 week (p<0.001), 0.
542 at 1month (p=0.001), 0.630 at 3 months (p<0.001). In control group, correlationcoefficient 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). DiscussionIn this study, we found a significantly lowerpostoperative IOP in eyes with PXF than in eyes without PXF. When comparing themagnitude of IOP decrease in both groups, we found a significant differencebetween both groups at one month (P=0.014) and three months (P=0.012), but notat one week (P=0.
111).We performed cataract surgery by two techniques: phacoemulsificationand PECCE. Several studies compared the effect of phacoemulsification on IOP ineyes with and without PXF.
Some studies found a significantly lowerpostoperative IOP in eyes with PXF than in those without.7-9 Other studies failed to detect any significant difference inpostoperative IOP between eyes with PXF and eyes without PXF.10-12 Similarly,We found an insignificant difference between eyes with PXF and eyes without PXFafter phacoemulsification as regarding postoperative IOP level, postoperative IOPreduction 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 theeffect of PECCE with PCIOL on IOP in eyes with and without PXF. Rustam et alperformed a prospective age- matched study on 40 eyes with PXF and 42 eyeswithout PXF.
The study found a significant IOP decrease at one month and threemonths postoperatively in both groups. However, there was insignificantdifference in postoperative IOP between both groups.13 In thisstudy, postoperative IOP was significantly lower than preoperative IOP at allfollow up visits in both groups after PECCE with PCIOL. In contrast to theabove study, this study found a significantly lower postoperative IOP at allfollow up visits in eyes with PXF than in eyes without PXF.
The exact mechanism of IOP reduction after cataractsurgery is unknown, but it may be due toincrease of the anterior chamber depth and widening of its angle after replacingprogressively growing crystalline lens by thin PCIOL, with backward rotation ofciliary body and relief of compression on trabecular meshwork and canal ofSchlemm.5In eyes with PXF, weak zonules causeforward shift of the crystalline lens with reduction in the anterior chamberdepth.1 Thus, it is thought that cataract surgery has a greaterimpact on deepening of the anterior chamber and widening of its angle in eyeswith PXF than in eyes without. This impact could explain why cataract surgerycauses greater IOP reduction in eyes with PXF than in eyes without. Güngör et al used Scheimpflug imaging system to compare thechange in ACD in eyes with PXF to eyes without PXF after phacoemulsification.
They found asignificantly more increase in ACD in eyes with PXF than in eyes without PXF.14Prostaglandins release after intraocularmanipulation cause disruption of the blood aqueous barrier with protein leakageand elevation of IOP for several hours. This is followed by prolonged hypotonysecondary to increased uveuoscleral outflow.15 Prostaglandins havetwo opposite effects on IOP; ocular hypertensive effect at high concentrationand ocular hypotensive effect at low concentration.16 Oshika et alfound that the blood ocular barrier disruption induced by cataract surgery(either phacoemulsification or PECCE) with abnormally high flare intensitypersist for up to six months postoperatively.
17 As the postoperativeinflammation is more severe in eyes with PXF than eyes without, it is expectedthat its hypotensive effect is more pronounced in eyes with PXF than in eyeswithout.18Shingelton et al suggested that the capsulecontraction after cataract surgery exert traction the ciliary body via thezonules, which leads to aqueous hyposecretion. They supported this theory by observing that IOPwas elevated by 2.2 mmHg after Neodymium:YAGcapsulotomy which led to partial relief of the capsular contracting force onthe ciliary body.19 Similarly, Jayne et al found a significant rise of IOPafter Neodymium:YAG capsulotomy which lasted for up to 3 years.20 Jacobi et al proposed that the irrigating solutionsused during cataract surgery (whose volume reaches upto 40 times the volume of the anterior chamber during PECCE and more than 200times during phacoemulsification) have a ‘rinsing’ effect on thepores of the trabecular meshwork.21 Based on this theory, theydeveloped a new technique called “trabecular aspiration” to wash theaccumulated 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 aspirationreduced IOP by 43% from baseline at 18 months postoperatively.
22Damji et al thought that lens removaleliminates iridolenticular friction and thus reduces the release of pigmentfrom the iris and exfoliation material from the lens and iris.8In this study, when we compared PECCE tophacoemulsification, we found that PECCE produced a greater IOP reduction thanphacoemulsification; however, the difference between the two techniques wasonly significant at one month. Similar to our finding, Saccà et al found thatPECCE reduced IOP more than phacoemulsification. They explained their findingby the greater prostaglandins release after PECCE than afterphacoemulsification.
23 It is known that longer corneoscleral woundof PECCE produces more irritation to the uveal tissues, leading to more releaseof inflammatory mediators compared to phacoemulsification.17In this study we found that higherpreoperative IOP was associated with greater postoperative IOP reduction(fig.4). Several studies reported the same observation.5, 24We found that age and gender did notsignificantly affect the amount of postoperative IOP reduction.
A similarfinding was reported by Shingelton et al4 and Poley et al.5The limitations of this study are: low number of eyes operated byphacoemulsification relative the number of eyes operated by PECCE, relativeshort period of postoperative follow-up. Our study did not evaluate the effectof cataract surgery on glaucomatous eyes.
Further studies are needed toevaluate the effect of cataract surgery on IOP in eyes with PXG and to compareits effect with combined cataract surgery and trabeculectomy or staged cataractand trabeculectomy surgery. In conclusion, this study found that cataractsurgery in eyes with PXF; either by PECCE or phacoemulsification, reduced IOPfor up to three months postoperatively from the preoperative level. This effectcan be considered as a protective or therapeutic option against development ofocular hypertension or PXG in eyes with PXF which is commonly occurred inelderly; for whom regular IOP monitoring is a difficult issue in developingcountries.