Dynamics of a Gas Permeable Contact Lens During Blinking

Abstract

The dynamics of a gas permeable contact lens during blinking are analyzed. The contact lens is considered to be a planar, circular, porous disk of specified permeability. On one side, the lens is in solid contact with the eyelids, while on the other, it is separated from the corneal surface by a thin tear film. The rigid-body dynamics of the lens are coupled with the fluid dynamics of the tear film, and a velocity slip condition is imposed at their interface. The coupled system of ordinary and partial differential equations is solved by a combination of analytical and numerical techniques subject to boundary conditions and physical constraints limiting the duration and extent of the motion of the lens. In addition to the contact lens aspect ratio, this work investigates the effects of those variables that characterize the porous nature of the lens such as the Darcy number and the effective slip coefficient. The motion of a permeable contact lens can be controlled by a proper choice of the lens material microstructure. In fact, analysis of the results indicates that the motion of the lens is enhanced by lower values of the slip coefficient and higher values of the Darcy number, independent of the lens thickness. In addition, it is found that thicker lenses as well as thicker tear films cause the lens to move faster.