Forces retaining a contact lens on the eye between blinks

The forces retaining a contact lens on the eye between blinks are analyzed using quasi-static equilibrium equations. The main forces are: (1) the surface tension forces around the contact lens periphery pulling the lens toward the cornea, (2) the reaction pressure force underneath the lens countering the effects of the surface tension, and (3) the weight of the lens. The reaction pressure force on the posterior side of the contact lens arises as a consequence of lubrication phenomenon. The centered lens can never be in static equilibrium. However, since the time period associated with the inertia effect in a thin-film system is much longer than the time between consecutive blinks, a quasi-static analysis is applied.