Etiology of corneal sensitivity changes accompanying contact lens wear.

Corneal touch threshold was monitored while corneal edema was experimentally induced by exposing the cornea to either an oxygen-free environment or hypotonic saline. No change in sensitivity occurred during these conditions. Contact lens wearers who were fully adapted to their lenses and did not develop corneal edema during wear showed an increase of 96% in corneal touch threshold. Refitting these subjects with an experimental contact lens which caused a 6% increase in corneal thickness did not further alter the corneal sensitivity. The decrease in corneal sensitivity accompanying contact lens wear is independent of corneal edema and is likely a result of sensory adaptation to a mechanical stimulant.