Postoperative corneal astigmatism in cataract extraction: diamond knife versus Beaver blade

Postoperative corneal astigmatism was studied in two groups of patients who had cataract extraction. The technique in both groups was identical except for the knife used for the partial-thickness limbal incision. In 49 patients the incision was performed with a Beaver blade and in 35 patients, with a diamond knife. Six weeks postoperatively the astigmatism was 1.27 +/- 0.90 diopters (D) in the diamond knife group, and 2.85 +/- 1.78 D in the Beaver blade group (P less than 0.0001). Sixty-one percent of the Beaver blade cases had with-the-rule astigmatism and 8% had no astigmatism. Thirty-one percent of the diamond knife cases had with-the-rule astigmatism and 26% had no astigmatism. At six months, the astigmatism was equal in both groups and practically identical to that found six weeks postoperatively in the diamond knife group. We conclude that incision of the limbal tissue with a diamond knife is associated with lower postoperative astigmatism and a more stable refractive state than incision with a Beaver blade.