Lubrication regimes in contact lens wear during a blink

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 12-18 kPa for initial eyelid wiper sliding speeds of 10-100 mm/s, with corresponding aqueous film thicknesses of 260-820 nm. 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. (C) 2013 Elsevier Ltd. All rights reserved.