Importance of Type and Direction of Eyelid Sliding to Mimic Blinking In Vitro for Dry Eye Disease and Contact Lens...

Establish a physiologically relevant in vitro ocular friction mode that simulates the natural curvature of the eyelid over the eyeball to investigate the friction mechanisms underlying blink-related discomfort due to contact lens wear (CLW) and dry eye syndrome (DED).

This study developed a pendulum friction device integrated with the UMT-3 TriboLab to simulate the natural curvature-following motion of the eyelid along the eyeball and measured the kinetic and static coefficients of friction (µk and µs, respectively) using fresh porcine eyelids and eyeballs, along with soft contact lenses (CLs) as tribo-pairs, under controlled speed, load, and sliding modes. Also, a relatively new parameter, relief period (RP), was used to compare different sliding motions and the presence of CL.

Tribological tests demonstrated that the natural swing motion consistently produced higher µk and longer RP values compared with artificial sliding or swing, underscoring the importance of sliding direction and mimicking natural blink. Natural swing had significantly higher µs and µk than the artificial sliding mode in a low-modulus CL, and it showed significantly higher µs than the other two artificial modes in a high-modulus CL. No significant difference in RP was observed for either CL.

Ocular tribology is strongly influenced by the direction of sliding. Natural swing motion that mimics blinking produced higher µk and longer RP than simplified sliding modes. These effects were more pronounced for a low-modulus lens. Accurately replicating the sliding direction is essential for realistic modeling of blinking-related friction.