Gaussian optics for photorefractive keratectomy. Increased predictability for larger diopter corrections.

Abstract

To evaluate clinically a formula based on spherical Gaussian optics for enhanced predictability of excimer photorefractive keratectomy (PRK) in both high and low degrees of myopia. Patients (24 eyes) were evaluated preoperatively with refractive measurements and corneal topography. After excimer PRK (3-24 months), postoperative remaining spectacle correction and corneal topography were measured. The attempted laser correction, calculated using algebraic equations, was compared with the achieved laser correction. The absolute laser correction error (mean +/- standard deviation), defined as the difference between the achieved and attempted laser corrections, was 0.37 +/- 0.31 diopter (D) for the 24 eyes. No significant difference was found in the error for attempted corrections greater than 6 D versus those less than 6 D. The use of a spherical Gaussian optics formulation results in accurate laser correction values for a wide range of myopia, even for large diopter corrections.