Purpose: To compare induced astigmatism and postoperative astigmatism of a 4 mm corneal superior incision to a 4 mm temporal incision for cataract phacoemulsification surgery.
Methods: Sixty eyes underwent cataract surgery for this prospective study. Thirty had a superior corneal incision (group 1) and 30 had a temporal incision (group 2). The incision was placed according to the pre operative astigmatism:temporal approach in case of against the rule astigmatism and superior location in case of with the rule astigmatism. The incision was enlarged to 4 mm just before implantation of a foldable lens. The patients had a pre operative and a post operative (day 1, 8, 30, 180) keratometry. Some had a corneal topography too. The surgically induced astigmatism was calculated using Naeser method.
Results: The incision having a relaxing effect on the meridian where it is placed, the surgically induced astigmatism is against the rule for a superior location and with the rule for a temporal location. At day 30 the mean surgically induced astigmatism was 0.98 diopter in group 1 and 0.58 in group 2. At ay 30 the postoperative astigmatism was 0.51 diopter against the rule in the first group and 0.13 diopter with the rule in the second group.
Conclusion: The superior corneal incision rarely allows to reach a minimum postoperative astigmatism as with a temporal location.