Distribution of oxygen across the surface of the human cornea during soft contact lens wear

PURPOSE: To determine whether tear mixing occurs beneath soft contact lenses, we examined the effect of blinking on the oxygen distribution across the corneal surface beneath a nonuniform thickness lens. METHODS: A custom-designed twin polarographic oxygen sensor assembly was used to simultaneously measure the equivalent oxygen percentage (EOP) at central and peripheral corneal locations of 10 human subjects beneath a -6.00 D thin-design hydroxyethyl mathacrylate (HEMA) lens. A -0.25 D lens served as a control. Each lens was worn for 5 min under static (no blinking) and dynamic (12 and 60 blinks/min) conditions. RESULTS: A significantly greater EOP (p = 0.006) was observed at the central (vs. peripheral) cornea during static and dynamic lens wear; central and peripheral oxygenation were unaffected by blinking. CONCLUSIONS: Tear mixing is insignificant beneath thin-design HEMA lenses; therefore, oxygenation across the corneal surface beneath such lenses is best predicted from the lens thickness profile rather than average thickness