Qualitative Investigation of Corneal Changes after Accelerated Corneal Collagen Cross-linking (A-CXL) by In vivo Confocal Microscopy and Corneal OCT

Purpose: To assess qualitative micro-morphological corneal changes by confocal microscopy and corneal OCT after accelerated corneal crosslinking (A-CXL) in keratoconic patients. Study design: Prospective non-randomized pilot study. Methods: 20 eyes of 20 patients, aged between 13 and 26 years (mean 22.6 years) underwent A-CXL by the KXL UV-A source (Avedro Inc. Waltham MA, USA). Patients were divided into 4 groups according to different riboflavin solutions and UV A powers.15 patients underwent epithelium-off A-CXL: 5 (Group 1) by riboflavin 0.1% plus dextran 20% at 12 mW/cm2 for 10 min; 5 (Group 2) at 30 mW/cm2 for 4 min; 5 (Group 3) by dextran-free riboflavin 0.1% plus HPMC at 30 mW/cm2 for 4 min and 5 (Group 4) by riboflavin 0.25% plus EDTA, BAK, TRIS epithelium-on A-CXL for 2 min and 40 sec. Micro-morphological analysis was assessed by in vivo HRT II confocal microscopy and corneal OCT. Results: Epithelium regenerated into 3 days. Sub-epithelial nerves disappeared after treatment regenerating into 6 months. Epithelium off A-CXL penetration, measured evaluating keratocytes loss at confocal microscopy and demarcation lines at corneal OCT, resulted at 180 μm on average in the Group 1, 160 μm in the Group 2, 150 μm in the Group 3. Epithelium-on A-CXL (Group 4) revealed a penetration at 80 μm on average. No endothelial damage was recorded in all groups. Conclusion: A-CXL shortened conventional CXL procedure under 20 minutes, being well tolerated. Its clinical efficacy needs to be determined in the mid-long term follow-up and in a large cohort of patients.