PHOTOREFRACTIVE KERATECTOMY USING THE SUMMIT SVS APEX LASER WITH OR WITHOUT ASTIGMATIC KERATOTOMY

The purpose of this study was to evaluate the results of myopic photor efractive keratectomy (PRK) with or without astigmatic keratotomy (AK) for different levels of intended correction by using the SVS Apex las er, Methods, This is a retrospective cohort study of 226 eyes that had PRK for myopia ranging from -1.0 to -7.6 diopters and 6 months of fol low-up. In addition, 64 of these eyes had AK for naturally occurring o r laser-induced astigmatism. Uncorrected visual acuity, spectacle-corr ected visual acuity, and corneal topography with quantitative descript ors of surface regularity (SRI) and surface asymmetry (SAI) were used to monitor the results of PRK with or without AK. Results, At 6 months , 95.6% eyes had an uncorrected visual acuity of 20/40 or better, 90% eyes were within +/-1.0 diopter of emmetropia, and 3.1% eyes lost two lines of best-corrected vision. No eyes lost more than two lines of be st-corrected vision. Mean refractive astigmatism was reduced, but mean SAI and SRI were increased, 6 months after PRK. Uncorrected vision, b est-corrected vision, and predictability decreased, whereas SAI and SR I increased, with increasing attempted correction. Conclusion, PRK, wi th or without AK, effectively reduced myopia in all eyes by 6 months a fter surgery. Predictability tended to decrease with increasing attemp ted correction, even for eyes with relatively low to moderate myopia. PRK may induce surface asymmetry and irregularity at 6 months, and the se alterations tend to be greater as the attempted correction increase s.