Friction and Lubrication of Eye/Lens/Lid Interface: The Effect of Lubricant and Contact Lens Material

Irritation of the eye in the case of contact lens users may imply dry eye syndrome (DES), commonly treated by eye drops. The paper focuses on measuring the friction coefficient with the simultaneous observation of lubricating film formation of the simulated eye/lens/lid interface. The experiments are performed in a pin-on-plate setup under the linear reciprocal motion. The contact is lubricated by twelve different solutions as the potential ingredients for eye drops, focusing on the role of mucin, buffer type, and molecular weight (MW) of hyaluronic acid (HA). Two commercially available contact lenses are studied, while overall lens performance is evaluated, among others. The results showed that the lens material, the presence of mucin, and the type of buffer have a decisive influence on the contact behavior. Specifically, it is concluded that the selection of eye drops should reflect the type of lens the wearers use and the conditions of their tear film. The appropriate ingredient for Acuvue Oasys and Biofinity contact lenses is suggested based on the score of the biotribological performance of the lubricant, taking both friction and lubrication into account.