Clinical Outcomes of Transepithelial Photorefractive Keratectomy According to Epithelial Thickness

PURPOSE: To investigate the clinical outcomes, vector parameters, and corneal aberrations of corneal wavefront-guided (CWFG) transepithelial photorefractive keratectomy (PRK), according to epithelial thickness. METHODS: This retrospective, comparative case series study included 91 eyes (91 patients) that underwent CWFG transepithelial PRK for myopic astigmatism. Epithelial thickness was less than 50 μ m in 48 patients and 60 μ m or greater in 43 patients. Clinical outcomes, including visual acuity, manifest refraction, vector parameters, and corneal wavefront aberration, were compared between the two groups. RESULTS: The mean uncorrected distance visual acuity, safety and efficacy indices, and aberrometric values were comparable between the two groups at 6 months after transepithelial PRK. The postoperative spherical equivalent was significantly different between the two groups: 0.05 ± 0.19 diopters (D) in the less than 50 μ m group and −0.05 ± 0.18 D in the 60 μ m or greater group ( P = .009). The difference between the two groups was 0.10 D, which is less than the theoretical difference because the epithelial remodeling pattern was different. There was a slight difference in slope between target induced astigmatism vector and surgically induced astigmatism vector (0.9979 in the less than 50 μ m group and 0.9145 in the 60 μ m or greater group; P = .025). CONCLUSIONS: Transepithelial PRK is an effective and safe treatment modality regardless of epithelial thickness. However, a difference in postoperative refraction is present between the two groups, and astigmatic correction may be less in patients with thick epithelium; hence, a new algorithm is needed that can be tailored in accordance with individual epithelial thickness. [ J Refract Surg. 2018;34(8):533–540.]