Résumé
To assess quantitative and qualitative microstructural changes at 3 months induced by corneal collagen Cross-Linking surgery in patients with progressive keratoconus using in vivo confocal microscopy (IVCM). Design and setting: prospective, non-comparative, monocentric observational case series. Department of Ophthalmology, University Hospital Center, Montpellier, France. Materials and methods: 19 eyes from 11 patients with progressive keratoconus were included between May 2022 and May 2024 at the Ophthalmology Department of the Gui de Chauliac University Hospital in Montpellier (a prospective, observational, non-comparative case series). All patients underwent accelerated protocol corneal collagen Cross-Linking surgery. Examinations were performed preoperatively and at 1 and 3 months postoperatively. Each visit included a slit-lamp examination and in vivo confocal microscopy of the cornea (Heidelberg Retina Tomograph III). Corneal topography (Pentacam, OCULUS) performed at 3 months postoperatively enabled correlation analysis between keratometric, pachymetric, and confocal microscopy data. The first visit and the 3-month follow-up included a lifestyle habits questionnaire completed either prospectively or retrospectively via phone interview. Results: IVCM after corneal Cross-Linking revealed a significant decrease in keratocyte density in the anterior and mid-stroma up to 1 month postoperatively (p<0.01), followed by an increase in these densities between the 1st and 3rd months postoperatively (p<0.01). The nerve plexus density significantly decreased (p<0.01) at each postoperative visit compared to preoperative data. No significant difference was observed in the posterior stroma or endothelial cell densities. Subgroup analyses showed a significant increase in mid-stroma keratocytes in the "frequent eye rubbing" group at 3 months (p=0.024), with no significant differences in other corneal layers. A significant decrease in mid-stroma keratocytes at 3 months was observed in the smoking group compared to non-smokers, without other significant differences in other corneal layers. Endothelial inflammation at 1 and 3 months was found in one of the two patients under a protocol with hypo-osmolar riboflavin. Corneal topography showed a non-significant reduction in maximum keratometry (p=0.055), a non-significant decrease in central 3mm keratometry (p=0.12), and a non-significant reduction in pachymetry at 3 months postoperatively (p=0.15). Correlation analysis did not reveal any correlation between the degree of keratocyte loss and pachymetry, mean keratometry, or maximum keratometry data. Conclusion: corneal collagen Cross-linking in eyes with progressive keratoconus induces a significant decrease in keratocytes in the anterior and mid-stroma, as well as substantial loss of the sub-basal corneal nerve plexus. Secondary endothelial inflammation following Cross-Linking with a hypo-osmolar riboflavin protocol was noted. Smoking and eye rubbing may influence post-Cross-Linking histological evolution.