Oxygen boost transepithelial corneal collagen crosslinking: 2-year ultrastructural results

To assess ultrastructural corneal changes induced by oxygen boost transepithelial crosslinking (OBXL) and its efficacy at 2 years. This pilot cohort study was conducted at the French National Reference Keratoconus Center in patients with progressive keratoconus. Corneal transepithelial CXL with an additional source of oxygen delivered through the goggles was performed. All patients who underwent surgery had an evaluation preoperatively, between 1 and 3 mo postoperatively, and at 6, 12 and 24 mo postoperatively. Biomechanical (Corvis ST), topographical (CASIA-2), and microstructural changes (using In Vivo Confocal Microscopy and Anterior Segment OCT) following this new technique were assessed. We also evaluated visual acuity and eye rubbing behavior. Ten eyes of ten patients were enrolled, with a mean age of 23.8 ± 4.9 years. A visible demarcation line was observed on AS-OCT with a mean depth of 414 μm ± 80.91 (89 % of the total thickness). We also noticed an anterior hyperreflective band with a mean depth of 214 ± 42.95 μm. At 6, 12 and 24 mo postoperatively, the Kmax, Kmin, Cyl and Corneal Thinnest Point were stable (p > 0.05). At 24 mo, there was significant improvement in BCVA. Compared to baseline, at the first postoperative visit, corneal sub-basal nerve density decreased, and keratocyte apoptosis was observed in all patients. Regarding eye rubbing, the number of patients who rubbed their eyes frequently decreased after CXL. This study confirmed the histological effects of OBXL and a deep corneal interaction that is effective in stabilizing keratoconus.