Factors affecting single-step transepithelial photorefractive keratectomy outcome in the treatment of mild, moderate, and high myopia: a cohort study.

Abstract

To investigate the effect of preoperative factors on visual acuity, higher-order aberrations (HOAs), and index of success for spherical change (S.IOS) after transepithelial photorefractive keratectomy (t-PRK) for treating different grades of myopia. This was a retrospective one-armed cohort study where patients with high, moderate, or mild myopia treated with single-step t-PRK using Amaris 500 Hz excimer laser were evaluated for visual acuity, refractive status, corneal topography, HOAs, S.IOS, and mean efficiency and safety index before and 6mo after surgery. A total of 154 eyes of 77 patients with mild (n=59), moderate (n=83), and high (n=12) myopia were reviewed. The efficiency and safety indices for vision recovery by single-step t-PRK were 98% and 100%, respectively. The achieved spherical equivalent (SE) was within 1 diopter (D) in 151 (98%) eyes. The median of the S.IOS was 1.18 [interquartile range (IQR) 1.0, 1.4]. The change in S.IOS was significantly correlated with age (P=0.007), 6.5 mm ablation zone (Mann-Whitney U test, P<0.01), and mild and moderate grade of myopia (Kruskal-Wallis test, P<0.001). Trefoil aberration, spherical aberration, and aberration coefficient types of HOA increased significantly (Wilcoxon test, P<0.001) 6mo post-surgery. There was a significant correlation between spherical aberration and aberration coefficient HOAs by myopia grades (P<0.05). Single-step t-PRK has promising short-term outcomes for refractive corrections and vision improvement to treat all three grades of myopia.