Tear flow under hydrogel contact lenses.

The tear replenishment rate under three different hydrogel lenses was determined with a slit lamp modified to serve as a fluorophotometer. Fractional tear volume replenishment rates under these lenses averaged 0.011 per blink, which is significantly lower than the 0.10 to 0.20 per blink reported for rigid lenses. These data suggest that the amount of oxygen delivered to the cornea by tear pumping for gel lenses is relatively small and that oxygen received by the cornea covered by a gel lens comes principally by diffusion through the material.