Computed Flow and Fluorescence Over the Ocular Surface

TL;DR

This paper develops a mathematical model to simulate tear film flow, evaporation, and fluorescence on the ocular surface, providing insights into dry eye syndrome and matching in vivo observations.

Contribution

It introduces a comprehensive mathematical model that integrates tear film dynamics, solute transport, and fluorescence, advancing understanding of ocular surface processes.

Findings

Model reproduces key experimental fluorescence patterns

Simulates tear film thinning and solute concentration changes

Aligns well with in vivo measurements of tear film behavior

Abstract

Fluorescein is perhaps the most commonly used substance to visualize tear film thickness and dynamics; better understanding of this process aids understanding of dry eye syndrome which afflicts millions of people. We study a mathematical model for tear film flow, evaporation, solutal transport and fluorescence over the exposed ocular surface during the interblink. Transport of the fluorescein ion by fluid flow in the tear film affects the intensity of fluorescence via changes in concentration and tear film thickness. Evaporation causes increased osmolarity and potential irritation over the ocular surface; it also alters fluorescein concentration and thus fluorescence. Using thinning rates from in vivo measurements together with thin film equations for flow and transport of multiple solutes, we compute dynamic results for tear film quantities of interest. We compare our computed intensity distributions with in vivo observations. A number of experimental features are recovered by the model.