Penetration depth of corneal cross-linking with riboflavin and UV-A (CXL) in horses and rabbits.
OBJECTIVE
CXL penetration depth is an important variable influencing clinical treatment effect and safety. The purposes of this study were to determine the penetration depth of CXL in rabbit and equine corneas in epithelium-on and epithelium-off procedures and to assess an ex vivo fluorescent biomarker staining assay for objective assessment of CXL penetration depth.


PROCEDURES
CXL treatment was performed according to a standardized protocol on 21 and 17 rabbit eyes and on 12 and 10 equine eyes with and without debridement, respectively. Control corneas were treated similarly, but not exposed to CXL. Hemicorneas were stained with either phalloidin and DAPI to visualize intracellular F-actin and nuclei, or with hematoxylin and eosin. Loss of actin staining was measured and compared between groups.


RESULTS
Epithelium-off CXL caused a median actin cytoskeleton loss with a demarcation at 274 μm in rabbits and 173 μm in horses. In non-CXL-treated controls, we observed a median actin cytoskeleton loss with a demarcation at 134 μm in rabbits and 149 μm in horses. No effect was detected in the epithelium-on procedure.


CONCLUSIONS
CXL penetration depth, as determined by a novel ex vivo fluorescent assay, shows clear differences between species. A distinct effect was observed following epithelium-off CXL treatment in the anterior stroma of rabbits, but no different effect was observed in horses in comparison with nontreated controls. Different protocols need to be established to effectively treat equine patients with infectious corneal disease.
['Gallhoefer|Nicolin S|NS|', 'Spiess|Bernhard M|BM|', 'Guscetti|Franco|F|', 'Hilbe|Monika|M|', 'Hartnack|Sonja|S|', 'Hafezi|Farhad|F|', 'Pot|Simon A|SA|']
D000818:Animals D015415:Biomarkers D016923:Cell Death D003315:Cornea D003432:Cross-Linking Reagents D005456:Fluorescent Dyes D006736:Horses D017319:Photosensitizing Agents D011817:Rabbits D012256:Riboflavin D046509:Tissue Culture Techniques D014466:Ultraviolet Rays
penetration depth CXL horse rabbit fluorescent biomarkers infectious keratitis