Modelling transport in the anterior segment of the eye.

Abstract

To model the kinetics of substances, particularly applied substances, in the anterior segment. A simple computational model was developed to describe portions of the anterior segment. First, a two-dimensional vertical slice through the center of a simplified anterior segment was modeled. This incorporated movement of substances by diffusion and by bulk flow in the anterior segment convectional flow. Second, movement by bulk flow in the secretory inflow and drainage of aqueous humor was included. Lastly, the model was extended to three-dimensional form, enabling it to deal with portions of the anterior segment. The model was applied to a number of situations. First, the anterior chamber was loaded with a substance, and entry of fresh aqueous through the pupil was modeled. To model drug applications, a drug was focally applied to the cornea at the limbus, and the distribution of the drug was followed, including arrival at iris targets. In these situations, model results compared reasonably to published experimental observations and findings. For drug distribution, convectional flow was dominant; however, a good match to experimental findings required that secretory flow and drainage be included. A simple computational model appears to be able to give a reasonable description of anterior segment kinetics. Although the speed of secretory flow is small compared to the speed of convectional flow, it can exert substantial effects near the surface of the anterior chamber.