(551h) Evaporation Driven Instability in Tear Film

The study of tear film instability and its consequent rupture is an extended application of evaporation in thin films. A uniform thickness of tear film over corneal surface is critical for clear vision and hence is often seen as a measure of good eye health in ophthalmology.
We study the origin of instabilities in a tear film that leads to its consequent rupture during prolonged inter blink. We try to develop a mathematical model to provide a rigorous explanation to experimental observation of tear film break up. Till date, there is no one comprehensive theory that lucidly defines the define the phenomena of rupture in a tear film.
We validate our numerical simulation techniques using a 2 – D model of non–linearized and coupled equations based on locally elevated rate of evaporation. We then use this numerical technique to translate the model to a 3 -D domain to add another dimension of understanding to the phenomena. The simulation results from experimental observations are compared and reasonable correlation is found between the two. The model efficiently captures and employs the theory of evaporation driven instability in a tear film that originates upon a rupture in lipid layer. The study also incorporates a thorough analysis on several key parameters including the surface tension at tear film interface, water permeability through corneal surface and thin-film disjoining forces.