Parameter Estimation for Mixed-Mechanism Tear Film Thinning

TL;DR

This paper develops a mathematical model to estimate tear film breakup parameters by fitting fluorescence imaging data, revealing that evaporation and tangential flow jointly influence tear breakup dynamics.

Contribution

Introduces a novel parameter estimation method for tear film breakup mechanisms using model fitting to in vivo fluorescence data.

Findings

Tear breakup often involves both evaporation and tangential flow.

Best-fit models suggest combined mechanisms lead to faster tear breakup.

Multiple mechanisms may explain similar tear breakup phenomena.

Abstract

Etiologies of tear breakup include evaporation-driven, divergent flow-driven, and a combination of these two. A mathematical model incorporating evaporation and lipid-driven tangential flow is fit to fluorescence imaging data. The lipid-driven motion is hypothesized to be caused by localized excess lipid, or "globs." Tear breakup quantities such as evaporation rates and tangential flow rates cannot currently be directly measured during breakup. We determine such variables by fitting mathematical models for tear breakup and the computed fluorescent intensity to experimental intensity data gathered in vivo. Parameter estimation is conducted via least squares minimization of the difference between experimental data and computed answers using either the trust-region-reflective or Levenberg-Marquardt algorithm. Best-fit determination of tear breakup parameters supports the notion that evaporation and divergent tangential flow can cooperate to drive breakup. The resulting tear breakup is typically faster than purely evaporative cases. Many instances of tear breakup may have similar causes, which suggests that interpretation of experimental results may benefit from considering multiple mechanisms.