Corneal ablation patterns to correct for spherical aberration in photorefractive keratectomy

Purpose: To determine the spherical aberration introduced by photorefractiv e keratectomy (PRK) and customize ablation patterns to compensate for this aberration and improve post-PRK visual performance. Setting: Department of Ophthalmology, University of Arizona, Tucson, Arizon a, USA. Methods: Presurgical and postsurgical corneal topography of 16 patients who had PRK with the Summit OmniMed laser were obtained. The data were applied to a schematic eye model, and exact ray tracing was used to determine the introduction of spherical aberration from the procedure. Optimization routi nes were used to determine the ideal ablation pattern. Results: The magnitude of the spherical aberration introduced into the eyes after PRK increased with the level of attempted correction. The theoretica l ideal ablation pattern requires additional flattening of the ablation per iphery to avoid the introduction of spherical aberration. Conclusions: Current PRK ablations introduce spherical aberration into the eye. Modifying the existing ablation algorithms to compensate for spherical aberration may boost postoperative visual performance. (C) 2000 ASCRS and ESCRS.