Penetration of fluorescein across the rabbit cornea from the endothelial surface

Abstract

Purpose: To model the kinetics of penetration of fluorescein across the cornea from the endothelial surface.

Methods: Rabbit corneas mounted in vitro were exposed to fluorescein at their endothelial surface. Trans-corneal fluorescence were acquired periodically for 6 h using a custom-built confocal microfluorometer. The profiles were then employed to fit a kinetic model for calculation of permeability and diffusion coefficients across the cellular layers and stroma, respectively.

Results: At the endothelium-stroma and stroma-epithelium interfaces, the fluorescence profile exhibited sudden jumps. In each case, the fluorescence was higher at the stroma, indicating reduced partitioning of the dye into the lipid-rich cellular layers. The stroma did not swell significantly until 180 min of perfusion. The fluorescence profiles reached a pseudo-steady state at ~6 h. A transport model, which included convective and diffusive fluxes into the stroma, showed a good fit to the trans-corneal profiles at different time points. The estimated permeability coefficients for the cellular layers were close to the values reported previously, but the diffusion coefficient of fluorescein in the stroma was found to be smaller than the values obtained previously using Ussing chambers.

Conclusions: The penetration of fluorescein could be modeled accurately by a combination of diffusion and convection.