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Jean-Louis Bourges, Chadi Mehana, Laurent Jonet, Michèle Savoldelli, Christophe Panthier, Francine F Behar-Cohen; Cross-linking and photoablative keratectomy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4853.
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© ARVO (1962-2015); The Authors (2016-present)
Refractive or therapeutic photoablations have been proposed in association with collagen cross-linking (CXL) protocols, despite riboflavin masks part of ultraviolet (UV) at excimer’s wavelengths. We aimed therefore at investigating photoablation depths resulting from excimer laser treatment on human corneas exposed to Riboflavin and UV.
Human experimental corneas were obtained from the Banque Francaise des Yeux. Experiments were conducted in the department of ophthalmology at Hotel-Dieu hospital, Paris.We separated experimental corneas in 3 groups of treatment: Group BSS (n=3) exposed to BSS only, group B2 (n=3) exposed to Riboflavin and group B2-UV (n=4) exposed to Riboflavin then irradiated with UV 10 mW/mm2-9 min. All cornea were then subjected to a myopic 4 D PRK (intended 61 µm depth). Corneas were photoablated on half of a 6.5mm central area, by separating the optic zone (OZ) with a PMMA plate. The central corneal thickness (CCT) was measured by US pachymetry before BSS/Riboflavin exposure, and after PRK. Corneas were then fixed and processed for optical microscopy. The maximal depth of ablation was quantified on semithin section in each group at the ablation transition line within a 1 mm central area.
Mean (±SD) CCTs of Group BSS, B2 and B2-UV were initially 628±3 µm, 729±2 µm and 665±1 µm. All CCTs decreased after exposure and before PRK from 12%, 20% and 37% respectively. Mean photoablation depths (±SD) were BSS=113±30 µm, B2=103±46 µm and B2+UV=105±13 µm.
Corneal edema interferes with excimer laser by enhancing depth of photoablation. The full collagen cross-linking procedure seems to limit PRK mean photoablation depths compared to BSS or Riboflavin alone.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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