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 tenses, 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.