Early corneal epithelial complications of combined trans-epithelial and accelerated collagen cross-linking in treatment of keratoconus

Abstract

PURPOSE: Trans-epithelial collagen crosslinking (CXL) benefits conventional epithelium off CXL by its ability to avoid epithelial defect or complications related to epithelium healing. In our study, we combine trans-epithelial CXL with an accelerated irradiation protocol (18 mW/cm2 for 5 min) in order to shorten the time of irradiation. The purpose of this study is to report any early corneal epithelial complications after combined trans-epithelial and accelerated CXL in treating keratoconus. By far, trans-epithelial CXL with conventional irradiation settings (3 mW/cm2 for 30 minutes) have not yet reported any epithelial related complications. SETTING: Department of Ophthalmology, Queen Mary Hospital, Hong Kong. METHODS: 7 patients and 11 eyes with topography evidence of progressive keratoconus were included. All patients underwent the combined trans-epithelial technique with an accelerated collagen crosslinking. Solution containing 0.25% riboflavin, 1.2 % HPMC and 0.01 % Benzalkoniumchloride were instilled every 2 minutes for 30 minutes, followed by 18 mW/cm2 UVA irradiation for 5 minutes at a working distance of 5cm (with continued application of the solution every 2 min). Complications of treatment were reported. RESULTS: A total of 7 eyes (64%) developed early corneal epithelial complications. 5 eyes (45%) developed large epithelial defect as large as the size of the irradiated area within the first week of operation. The other 2 eyes from the same patient resulted in diffuse punctate epithelial erosions. 1 eye with epithelial defect developed dendritic ulcer shortly after healing of the epithelial defect, which resolved after a course of topical acyclovir treatment. The early corneal stromal haze was seen only in those eyes with post-operative epithelial defects, but not in other eyes in which the epithelium remained intact. CONCLUSIONS: 64% of patients developed epithelial complications after combined trans-epithelial and accelerated CXL protocol. We propose the result to be due to increased intensity of UVA irradiation, which might have loosened tight junctions in the corneal epithelium, thus leading to epithelial defects. As a result, the main advantage of trans-epithelial technique in preserving the epithelium has been defeated. This study concludes that combined trans-epithelial and accelerated CXL protocol has no additional benefit in the treatment of keratoconus, hence we propose to continue with conventional UVA irradiation protocol if trans-epithelial technique is to be used.