Corneal astigmatism induced by superior versus temporal corneal incisions for extracapsular cataract extraction

Abstract

We tested the hypothesis that superior corneal sections induce a shift to 'against-the-rule' astigmatism and temporal corneal sections lead to the preferred 'with-the-rule' astigmatism. We conducted a prospective randomised trial of superior versus temporal corneal incisions in extracapsular cataract surgery in a hospital practice. Thirty nine eyes of 37 patients were included. The induced astigmatism was analysed by three methods. When analysed by Cravy's method of induced astigmatic cylinders, the superior incision induced a greater degree of 'with-the-rule' astigmatic cylinder prior to sutures removal on day 77 (P < 0.049). Long term, the temporal incision produced 1.44 dioptre of 'with-the-rule' astigmatism, while the superior section produced 0.08 dioptre of 'against-the-rule' astigmatism (P < 0.001). The results of this small trial indicates that the superior corneal incision produces significantly less astigmatism than the temporal incision. The temporal incision induces a moderate degree of 'with-the-rule' astigmatism.