Conservative Treatment of Keratoconus by Riboflavin-UVA-Induced Cross-Linking of Corneal Collagen: Qualitative Investigation of Corneal Epithelium and Subepithelial Nerve Plexus Regeneration by in vivo HRT II System Confocal Microscopy in Humans

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Abstract
Purpose: To assess corneal tissue modifications after riboflavin-UVA-induced cross-linking of corneal collagen in patients with progressive keratoconus as well as regeneration of epithelium and subepithelial nerve plexus by in vivo HRT II system confocal microscopy in humans. Methods: Ten patients with progressive keratoconus were treated by riboflavin-UVA-induced cross-linking of corneal collagen, involving assessment of ultrastructural modifications of the corneal epithelium and subepithelial nerve plexus by HRT II system confocal microscopy. Treatment included instillation of 0.1% riboflavin-20% dextrane solution 5 minutes before UVA irradiation and every 5 minutes for a total of 30 minutes. Radiant energy was 3 mW/cm2 or 5.4 Joule/cm2 and the source was dual UVA (370 nm) light-emitting led. The protocol included the operation followed by antibiotic medication and eye dressing with a soft therapeutic contact lens. Changes in epithelium and subepithelial and stromal nerve plexus were assessed by HRT II system confocal microscopy in vivo. Results: After 5 days of soft contact lens wearing corneal epithelium has a regular morphology and density. Disappearance of subepithelial stromal nerve fibers was observed in the central irradiated area where, 1 month after the operation, initial reinnervation was microscopically observed. No changes in nerve fibers were observed in the peripheral untreated with a clear lateral transition between the two areas. Six months after the operation, the anterior subepithelial stroma was recolonized by nerve fibers with restoration of corneal sensitivity. Conclusions: HRT II system confocal microscopy confirms corneal epithelium restore and reinnervation after riboflavin-UVA-induced collagen cross-linking directly in vivo in humans.