Effect of an elliptical optical zone on outcome of photoastigmatic refractive keratectomy.

Background: This study presents the effect of an elliptical optical zone on the accuracy of correction of astigmatism in patients undergoing photorefractive astigmatic keratectomy (PARK) for myopic astigmatism.

Methods: We reviewed a consecutive case series of 102 eyes that underwent PARK with a Nidek EC-5000 excimer laser by a single surgeon. Group A consisted of 50 eyes treated using a circular optical zone of 6.5 mm x 6.5 mm with a 7.5-mm x 7.5-mm transition zone. Group B consisted of 52 eyes treated using an elliptical optical zone of 5.5 mm x 6.5 mm with a 6.5-mm x 7.5-mm transition zone. Refraction was measured preoperatively and postoperatively, and vector analysis was used to study the change in astigmatism induced by surgery.

Results: Mean correction index improved from 75% in Group A to 100% in Group B. Mean angle of error was reduced from 15.8 degrees in Group A to 7.5 degrees in Group B. Hyperopic shift was reduced from +0.70 D in Group A to +0.20 D in Group B.

Conclusions: Excimer laser photorefractive astigmatic keratectomy using an elliptical optical zone improved the correction index for astigmatic change and reduced the mean angle of error. An elliptical optical zone is more effective than the circular optical zone for the treatment of astigmatism in patients with compound myopic astigmatism.