Abstract
Purpose :
To determine the riboflavin concentration in the posterior corneal stroma, Descemet's membrane and endothelium prior to UV-irradiation in CXL.
Methods :
Five human de-epithelialized cadaver corneas were mounted into artificial anterior chambers. After the establishment of stable physiological hydration, 0.1% riboflavin solution was applied onto the anterior surface. Two-photon microscopy was used to determine fluorescence intensity and SHG-signals throughout each cornea with a step size of 2.5 µm. To determine the absolute riboflavin concentration, corneas were saturated with 0.1% riboflavin and measured a second time by two-photon microscopy.
Results :
The topical application of 0.1% riboflavin results in a riboflavin concentration that is decreasing in the posterior stroma to 0.03%. Inside Descemet's membrane and endothelium, the concentration drops further to about 0.013% at the interface to aqueous. Local riboflavin distribution indicates a predominantly paracellular passive diffusion of riboflavin into the anterior chamber.
Conclusions :
The experimentally determined (0.015%) riboflavin concentration at the endothelium shows a substantial discrepancy of a factor of 1.7 to the previously theoretically calculated 0.025%. A lower riboflavin concentration at the endothelium may enable higher radiant exposures and further improve the efficacy of CXL.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.