Abstract
Purpose: :
Collagen crosslinking by the photosensitizer riboflavin and ultraviolet A-light is an effective means for stabilizing the cornea in keratoconus. The corneal epithelium represents a barrier for the molecules with molecular weight greater than 100, and riboflavin’s molecular weight is more than three times that. A new "transepithelial riboflavin" [Ricrolin TE® Sooft, Italia] preparation with modified physiochemical properties would allow to penetrate the cornea through the epithelium. The purpose of this study was to evaluate the distribution and concentration of transepithelial riboflavin in the corneal stroma compared to "standard riboflavin" [Ricrolin® Sooft, Italia].
Methods: :
In 12 rabbit eyes, the central corneal epithelium was removed, and a standard solution of riboflavin 0.1% in 20% dextran was applied each minute for 30 minutes. In 12 rabbit eyes, the epithelium was not debrided, and transepithelial riboflavin was applied with the same protocol. Four rabbit eyes were used as controls. Trephined corneal buttons were examined using confocal fluorescence microscopy. Stromal riboflavin distribution was determined by measuring riboflavin fluorescence in optical sections at 10 microm intervals through the entire cornea. Riboflavin concentrations were determined by high-performance liquid chromatography (HPLC) in stroma and aqueous humor.
Results: :
Transepithelial riboflavin does not appear to fully load the corneal stroma using the current clinical procedure. The uptake appears to be limited to the anterior approximately 200 microm. Control samples did not show a riboflavin emission peak. With transepithelial riboflavin with epithelium, the mean riboflavin concentration was 3 times less than the mean concentration with standard riboflavin without epithelium.
Conclusions: :
Distribution and concentration in the corneal stroma of transepithelial riboflavin without de-epithelialization appear to be less pronounced than after standard riboflavin with de-epithelialization.
Keywords: keratoconus • cornea: basic science • cornea: stroma and keratocytes