Patterns of late corneal scarring after photorefractive keratectomy in high and severe myopia

Abstract

ObjectiveTo study the correlation between scarring 1 year after photorefractive keratectomy (PRK), final refraction, and degree of myopia. DesignA retrospective, noncomparative case series. ParticipantsOne hundred twenty eyes of 78 patients underwent PRK for high and severe myopia. Thirty-nine eyes had a pre-PRK spherical equivalent (SE) between −9.5 and −18.25 diopters (D) (severe myopia). Eighty-one eyes had a pre-PRK SE between −6.25 and −9.25 D (high myopia). Follow-up time ranged between 12 and 37 months with a mean of 18.2 months. InterventionMultizone PRK with the VISX 20/20 excimer laser. Main outcome measuresCorneal scarring, final best-corrected visual acuity (BCVA), and refraction. ResultsThere were 71.7% of eyes with severe myopia and 60.5% of eyes with high myopia found to have any pattern of stromal scarring, which was classified as focal, semiannular, annular, and discoid. Discoid scars were rare (6.6%) and found in 12.8% of severe myopic eyes compared to 3.7% of high myopic eyes. Only 50% of the eyes with a discoid scar achieved final BCVA between 6/6 and 6/9 compared to 81.6% of the eyes with a clear cornea. The severe myopic eyes with a discoid scar had the highest level of final undercorrection (−5.0 D) compared to a maximum of −1.5 D in the high myopia group. The severe myopic eyes with a discoid scar had a higher number of retreatments (4 of 5) compared to the high myopia group (1 of 3). Other types of scars were less clinically significant. ConclusionsPhotorefractive keratectomy was efficient in the correction of high myopia but less so in severe myopia, in which discoid scarring was more frequent and more clinically significant, being associated with significant regression. Other types of scarring were less clinically significant.