Transepithelial Corneal Cross-linking with Supplemental Oxygen in Keratoconus Treatment - Corneal Stromal Demarcation Line and Safety

Purpose: To evaluate the corneal stromal demarcation line and safety of transepithelial corneal cross-linking (CXL) with supplemental oxygen in progressive keratoconus treatment. Methods: This is a retrospective review of 25 patients with progressive keratoconus who underwent epithelial-on CXL with supplemental oxygen from December 2019 to February 2022. Outcomes measured include corneal stromal demarcation line depth, volume of cornea treated, endothelial cell count, best-corrected visual acuity, keratometric parameters and post-treatment adverse events. Results: 25 eyes of 25 patients were included and mean age was 28.3 years. Mean follow-up period was 11.5 +/- 1.39 months. Pre-operatively, mean +/- standard deviation (SD) of K1, K2, Kmax and minimal corneal thickness were 45.9D +/- 3.79D, 50.2D +/- 4.83D, 57.5D +/- 6.98D and 482.3um +/- 36.8um respectively. There is no significant difference between pre and post-treatment corneal topographic parameters. There was improvement in BCVA post-treatment. The mean post- treatment corneal stromal demarcation line depth was 367.3 +/- 89.8um. The volume of treated cornea including the central corneal epithelial thickness was 73.3 +/- 4.39%. There was no reduction in endothelial cell count (ECC) post-procedure (pretreatment mean ECC +/- SD: 2695.4 +/- 224.5 cells/mm(2), post-treatment ECC 2730.1 +/- 252.0 cells/mm(2), p-value = 0.33). Post-treatment corneal haze was mild and seen in 8 patients postoperatively. One patient developed a non-visual axis involving stromal infiltrate that resolved with topical broad-spectrum anti-microbials. Conclusion: Trans-epithelial CXL with supplemental oxygen for keratoconus treatment achieved comparable corneal stromal demarcation line depth comparable to that of conventional epithelial-off corneal cross-linking and had a similar safety profile.