Changes in Central Corneal Epithelial Thickness after Transepithelial Photorefractive Keratectomy for Low and Moderate Myopia

Abstract

Objective: To observe the changes in the central corneal epithelium thickness (CCET) after transepithelial photorefractive keratectomy (TPRK) in low and moderate myopia patients. Methods: This was a retrospective case series study. Sixty-two myopes (114 eyes) were recruited who underwent TPRK at the Eye Hospital of China Academy of Traditional Chinese Medicine from January 2015 to June 2016. Patients were divided into two groups based on spherical equivalence (SE) refractive error: a low myopia group (-3.00 D to -1.25 D) and a moderate myopia group (-6.00 D to -3.25 D). Both groups underwent testing for uncorrected visual acuity (UCVA), SE, and CCET and were compared preoperatively and postoperatively at 1 week, 2 weeks, 1 month, 3 months, 6 months and 1 year. Preoperative and postoperative changes were analyzed with two independent samples t tests and repeated measures analysis of variance. Results: The two groups had significant differences in both UCVA and SE preoperatively (t=6.605, P=0.01; t=15.374, P=0.01). There were no significant differences between BCVA and CCET preoperatively (both P>0.05). The CCET values for the low myopia group were relatively higher than that for the moderate myopia group 1 week postoperation (t=3.362, P=0.01), but there were no significant differences at the other time points. Between the two groups and within each group at postoperative observation time points, UCVA and SE were not statistically significant. For CCET, except for between postoperative 1 month and 2 weeks, between postoperative 6 months, 1 year and preoperative without difference. And there was with difference between time points (P<0.05). Conclusions: In the early stage after TPRK, CCET in the low myopia group recovers faster than that in the moderate myopia group. The CCET in both groups is restored to preoperative levels after 6 months, and remains stable. TPRK surgical treatments for visual acuity in low and moderate myopia has a high predictability and a stable SE. Key words: myopia; transepithelial photorefractive keratectomy; central corneal epithelium thickness