Long-term Comparison of Combined t-PTK and CXL (Cretan Protocol) Versus CXL With Mechanical Epithelial Debridement for Keratoconus

PURPOSE: To compare the long-term outcomes of corneal cross-linking (CXL) for the treatment of keratoconus using two different techniques for epithelial removal: transepithelial phototherapeutic keratectomy (t-PTK) and mechanical epithelial debridement. METHODS: In this prospective, comparative, interventional case series, 26 patients (30 eyes) with progressive keratoconus underwent CXL treatment. Fifteen eyes (13 patients) underwent epithelial removal with t-PTK (Cretan protocol) and 15 eyes (13 patients) underwent mechanical epithelial debridement (Dresden protocol) during CXL. Visual, refractive, and keratometric outcomes were evaluated preoperatively and at 1, 2, 3, and 4 years postoperatively. RESULTS: No intraoperative or postoperative complications were observed in any of the patients. In the Cretan protocol group, mean uncorrected (UDVA) and corrected (CDVA) visual acuity improved from 0.99 ± 0.42 and 0.33 ± 0.28 logMAR preoperatively to 0.75 ± 0.32 ( P = .018) and 0.21 ± 0.16 ( P = .024) logMAR at 4 years postoperatively, respectively. In the Dresden protocol group, mean UDVA improved from 0.83 ± 0.47 logMAR preoperatively to 0.63 ± 0.40 logMAR ( P = .033) at 4 years postoperatively, whereas mean CDVA did not demonstrate a statistically significant improvement postoperatively ( P > .05). In the Cretan protocol group, mean corneal astigmatism improved from −6.19 ± 4.54 diopters (D) preoperatively to −4.68 ± 3.10 D ( P = .041) at last follow-up, whereas in the Dresden protocol group there was no statistically significant difference postoperatively ( P > .05). CONCLUSIONS: Epithelial removal with t-PTK during CXL (Cretan protocol) resulted in better visual, refractive, and keratometric outcomes compared with mechanical epithelial debridement over a long-term follow-up. [ J Refract Surg . 2019;35(10):650–655.]