Effects of optimized photorefractive keratectomy (PRK) operation on the asphericity and high-order aberration changes

Optimized is a common and important method in which aberrations are created by the device and the surgeon, but high-grade aberrations are out of the surgeon's control and are induced by the device in the patient. The aim of this study was the evaluation of out-of-control high-order aberration changes before and after PRK surgery and these impact on vision outcome.

In this before and after clinical trial study, we recurred 24 patients consist of 48 eyes. For the patients with myopic astigmatism, before the operation, a complete visual examination (visual acuity, refraction, etc.) and imaging including orbscan, zywave, and topolyzer were performed and tests were repeated six months after surgery. The results were compared before and after surgery.

24 patients included 8 males (33.3%) and 16 females (66.7%) with a mean age of 29±5 years recurred in the study. The total higher-order aberration increased after operation. There was no significant difference between the third and fourth-order corneal
aberrations before and after the operation. The ocular and corneal high-order aberration was increased. Mean asphericity was similar before and after the operation. Also, significant correlations among spherical equivalent, total high order abbration, and occular abbaration were found.

Regarding our study, eye sporadic defect improved after the operation but it would never achieve the optimal goal. According to the findings, it seems that the optimized method with the Allegretto EX500 device, despite its superiority over the conventional method, still induces high-grade aberrations and changes the asphericity from prolate to oblate mode. However, it improves refraction, which affects the quality of patients' vision.