GAUSSIAN OPTICS FOR PHOTOREFRACTIVE KERATECTOMY - INCREASED PREDICTABILITY FOR LARGER DIOPTER CORRECTIONS

Purpose:: To evaluate clinically a formula based on spherical Gaussian optics for enhanced predictability of excimer photorefractive keratec tomy (PRK) in both high and low degrees of myopia. Methods: Patients ( 24 eyes) were evaluated preoperatively with refractive measurements an d corneal topography. After excimer PRK (3-24 months), postoperative r emaining spectacle correction and corneal topography were measured. Th e attempted laser correction, calculated using algebraic equations, wa s compared with the achieved laser correction. Result: The absolute la ser correction error (mean +/- standard deviation), defined as the dif ference between the achieved and attempted laser corrections, was 0.37 +/- 0.31 diopter (D) for the 24 eyes. No significant difference was f ound in the error for attempted corrections greater than 6 D versus th ose less than 6 D. Conclusions: The use of a spherical Gaussian optics formulation results in accurate laser correction values for a wide ra nge of myopia, even for large diopter corrections.