The impact of Preoperative Epithelium on Transepithelial Photorefractive Keratectomy for the Treatment of Hyperopia and Mixed Astigmatism

Purpose: To calculate the impact of the refractive power associated with the epithelial thickness in transepithelial refractive corrections Setting: Aurelios Augenzentrum Recklinghausen, Germany Methods: We analyzed the impact of the epithelium in a consecutive retrospective group of hiperopic eyes treated with TransPRK with the AMARIS 1050 RS laser platform (Schwind Eye-Tech Solutions, Kleinhostheim, Germany) with a minimal follow-up of 4 months. The group of 95 treated eyes had an average age of 36 years. The preoperative mean sphere was +1.6 dioptres (D) with a range till +5D, and the mean cylinder was -2.16 D with a range till -5.75D. For the epithelium measurements, we used the anterior segment optical coherence tomography MS-39 (CSO, Florence, Italy). Results: The refractive outcome showed a mean sphere of -0.03 D (range -0.5 to 1 D) and a mean cylinder of -0.33 (range -1.75 to 0 D). 93% and 98% of the cases had 0.5D, 1D, respectively, or less of spherical equivalent refractive error. The epithelium showed preoperative toricity, correlating to the preoperative manifest astigmatism. Preoperatively, at 6 mm, the epithelium showed compensational effect of ~15% of the refractive astigmatism (12% for cardinal and 18% for oblique astigmatism); whereas for 3mm the compensation accounted for ~25% of the refractive astigmatism (21% for cardinal and 31% for oblique astigmatism). No correlation was found postoperatively. Conclusions: The preoperative toricity of the epithelium is correlated with the amount of preoperative refractive astigmatism. No systematic correlation was found between preoperative epithelium and refractive deviations after hyperopia transepithelial treatments.