Lubrication regimes in contact lens wear during a blink

• Published in: Tribology international 2013-07, Vol.63, p.45-50
• Main Authors: Dunn, Alison C., Tichy, John A., Urueña, Juan M., Sawyer, W.Gregory
• Format: Article
• Language: English
• Subjects: Biotribology; Boundary lubrication; Hydrogel contact lens
• ISSN: 0301-679X; 1879-2464
• DOI: 10.1016/j.triboint.2013.01.008

When the eyelid blinks down over a soft hydrogel contact lens, the tear film is partitioned or even consumed by the contact lens, introducing relative sliding on both sides against the corneal epithelium and the eyelid wiper. This work presents a numerical fluid model of the resulting pressures and sliding speeds in both pairs of sliding. Between the eyelid wiper and front curve surface, contact pressures ranged 12–18kPa for initial eyelid wiper sliding speeds of 10–100mm/s, with corresponding aqueous film thicknesses of 260–820nm. Maximum contact lens deflection was 0.5%. Sliding with those conditions points to a hydrodynamic regime, while the base curve/cornea sliding more likely falls in the boundary regime. A lubrication curve is presented for hydrated contacts under ocular sliding and loading conditions. ► A numerical model of lubrication on both sides of the contact lens was introduced. ► The lubrication model predicted hydrodynamic sliding at the maximum blink speeds. ► The lubrication model predicted boundary lubrication on the contact lens base curve surface and during slower ocular movements. ► The boundary regime is relevant and complex for contact lens friction.