Clinical Outcomes of Transepithelial Photorefractive Keratectomy According to Epithelial Thickness.

Abstract

To investigate the clinical outcomes, vector parameters, and corneal aberrations of corneal wavefront-guided (CWFG) transepithelial photorefractive keratectomy (PRK), according to epithelial thickness. 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 μm in 48 patients and 60 μm or greater in 43 patients. Clinical outcomes, including visual acuity, manifest refraction, vector parameters, and corneal wavefront aberration, were compared between the two groups. 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 μm group and -0.05 ± 0.18 D in the 60 μm 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 μm group and 0.9145 in the 60 μm or greater group; P = .025). 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.].