CORNEAL TOPOGRAPHY AFTER CATARACT-SURGERY WITH TUNNEL INCISION ON THESTEEPER MERIDIAN IN OBLIQUE AND INVERSE ASTIGMATISM

Scleral tunnel incision at the 12 o'clock-position for no-stitch catar act surgery can increase preexisting against-the-rule astigmatism by f lattening the vertical corneal meridian. An oblique axis can change by operative induction. We investigated, in a prospective study, whether reduction of such a preoperatively astigmatism could be induced by lo cating the tunnel incision on the steeper meridian. Eighteen eyes with senile cataract and against-the-rule or oblique astigmatism of at lea st 0.7 diopters were operated with a standardized 5x6 mm scleral tunne l incision and a 6 mm PMMA posterior chamber lens. We evaluated the as tigmatism with a videokeratoscope TMS-I preoperatively and about 6 mon ths after the surgery. The mean corneal astigmatism was 1.8 diopters p re- and 1.5 diopters postoperatively. A reduction of keratometric asti gmatism was leached in 72% of cases; 17% remained unchanged. The surgi cally induced astigmatism calculated by Jaffe's and Clayman's vector a nalysis was 0.68 diopters. The technique of scleral tunnel incision wi th lateral or oblique approach can reduce a preexisting against-the-ru le or oblique astigmatism.