Measurement and Prediction of Transient Transport across Sclera for Drug Delivery to the Eye

Abstract

Drug delivery to the eye for treatment of a number of important diseases involves non-steady-state transport across the sclera. Although the literature contains steady-state measurements of permeability, the transient transport properties of sclera have not been determined experimentally or described theoretically. In this study, carboxyfluorescein flux across human sclera is shown experimentally to approach a quasi-steady state with a lag time of 0.37 h. Because drug-sclera contact times in the body are often shorter than this, the use of steady-state permeability models will overpredict the amount of drug delivered to the eye. A theoretical model is also developed to describe the observed transient flux by accounting for both diffusion and solute binding within the sclera.