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Changes in keratometry following trabeculectomy

Poster Details

First Author: M.Radenkovic SERBIA

Co Author(s): G. Stankovic Babic   J. Djordjevic Jocic   P. Jovanovic   M. Zivkovic   S. Cekic   M. Trenkic Bozinovic     

Abstract Details


Trabeculectomy is the most common surgical procedure for long-term reduction of intraocular pressure (IOP) in glaucoma. Patients often complain of vision reduction for several months. Amongst other factors, corneal astigmatism appears to be altered. Different mechanism of astigmatism from that after cataract surgery was proposed. These changes may be due to surgically induced wound gape in trabeculectomy, diameter of overlying scleral flap wich allows the unsupported corneal edge of the trabeculectomy opening to sink slightly. Some patients develop a relative superior corneal steepening, others superior flattening and others complex regional changes independent to these patterns.


This research (patient examination) was conducted in glaucoma department of Eye Clinic (Clinical Center Nis) to evaluate corneal keratometry changes after trabeculectomy and potential influence to visual acuity postoperatively.


Statistic analysis (program SPSS18) was performed of obtained results before and after (day 7, 30, 60) conventional fornix based flap trabeculectomy, without antimetabolites, in 60 phakic eyes (60 patients) with Open Angle Glaucoma (OAG): 42 Primary Open Angle Glaucoma (POAG) and 18 exfoliative glaucoma (XFG).Examination tool: visual acuity according to Snellen chart, spalt lamp examination, keratometry of steep and flat meridian obtained at autokeratorefractometer.


Exfoliative Glaucoma (XFG) patients were older than POAG (p<0,05). Visual acuity was reduced for two lines (Snellen chart) from 0,4 to 0,2 after glaucoma operation and returned to preoperative level 60 days after (p<0,0001). There was no statisticaly significant difference in steep meridian values over time. Keratometric changes of flat meridian after trabeculectomy have revealed significant changes and steepening, from 42,62±1,53 D to 42,95±1,32 D (p<0,05). Corneal astigmatism values (D Sphere) changes significantly over time from 1,20±0,99 D Sphere to 1,27±1,06 D Sphere (day 7) and 0,82±0,79 D Sphere (day 60) (p<0,05).


The main characteristic of astigmatism after trabeculectomy are instability, unpredictable outcome, with frequent inversion and potential stabilization after 2-3 months. Autors noted shift towards 'with-the-rule' astigmatism and vertical steepening which returns to the pre-operative values. These clinical study concluded difference in the postoperative values of flat meridian in comparison to preoperative (p <0,05), without significant difference in steep meridian which explains a good refractive outcome. There is a difference in the postoperative value of corneal astigmatism in time interval of 2 months (p <0,05). Dynamic corneal changes could alter visual acuity with spontaneous recovery.

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