RT Journal Article
SR Electronic
T1 Topographic and keratometric astigmatism up to 1 year following small flap trabeculectomy (microtrabeculectomy)
JF British Journal of Ophthalmology
JO Br J Ophthalmol
FD BMJ Publishing Group Ltd.
SP 779
OP 782
DO 10.1136/bjo.83.7.779
VO 83
IS 7
A1 S A Vernon
A1 H J Zambarakji
A1 F Potgieter
A1 J Evans
A1 P B Chell
YR 1999
UL http://bjo.bmj.com/content/83/7/779.abstract
AB AIM To determine the induced corneal astigmatism by measuring the changes in manual keratometry and computerised corneal videokeratoscopy up to 1 year following small flap trabeculectomy (microtrabeculectomy). METHOD A prospective study of a case series of small flap trabeculectomy procedures performed at the 90 degree meridian on 16 eyes of 16 patients, all followed to 1 year postoperatively. Changes in manual keratometry and computerised videokeratoscopy (Eyesys) readings were analysed by vector analysis and vector decomposition techniques. RESULTS By vector analysis, the mean surgically induced refractive change (SIRC) cylinder power vectors induced at 1, 3, 6, and 12 months as measured by manual keratometry were 0.68, 0.38, 0.52, and 0.55 dioptres, and by keratography 0.75, 0.66, 0.59, and 0.64 dioptres. Vector decomposition on the induced vector cylinders on manual keratometry resulted in a “with the rule” mean vector of 0.52 and 0.22 dioptres at 1 and 3 months and an “against the rule” mean vector of 0.16 and 0.16 dioptres at the same time points (p=0.03 and 0.28 respectively). Vector decomposition at 6 and 12 months revealed no significant with the rule changes induced. Similar analysis on the videokeratoscopy results revealed significant induced with the rule astigmatism until 3 months, but not at 6 and 12 months postoperatively. CONCLUSION Small flap trabeculectomy (microtrabeculectomy) produces smaller changes in corneal curvature that resolve sooner than previous reports of larger flap techniques.