Dewetting characteristics of contact lenses coated with wetting agents.

Hypothesis: Although wetting agents have been developed to limit tear film dewetting over contact lenses, systematic analyses correlating wetting agent properties to mechanisms of the tear film destabilization are not readily available. Clarifying destabilization characteristics across key physio-chemical variables will provide a rational basis for identifying optimal wetting agents.

Experiments: We employ an in-house, in vitro platform to comprehensively evaluate drainage and dewetting dynamics of five wetting agents across seventeen different formulations and two model tear film solutions. We consider the film thickness evolution, film thickness at breakup, dewetted front propagation, and develop correlations to contact angle to compare the samples.

Findings: Zwitterionic wetting agents effectively stabilize the tear film by reducing the film thickness at the onset of dewetting, and delaying the propagation of dewetted regions across the lens. Furthermore, tuning wetting agent surface concentrations and utilizing binary mixtures of wetting agents can enhance wetting characteristics. Finally, despite disparities in wetting agent molecular properties, the time to dewet 50% of the lens scales linearly with the product of the receding contact angle and contact angle hysteresis. Hence, we fundamentally establish the importance of minimizing the absolute contact angle and contact angle hysteresis for effective wetting performance.