Silicone elastomer lens wear induces less overnight corneal edema than sleep without lens wear.

Corneal thickness was measured on awakening in both eyes of ten subjects who slept with a silicone elastomer lens in one eye only. The mean corneal edema level with the silicone lens after eight hours of sleep was 2.0 +/- 2.0% and was significantly lower (p less than 0.01) than the level in the eye that did not wear a lens (3.6 +/- 2.1%). This indicates that the oxygen level supplied to the anterior cornea during sleep with silicone elastomer lenses is higher than without a lens. We hypothesize that the lower overnight swelling with the silicone lenses is a result of reduced resistance to oxygen flow from the eyelid capillaries to the corneal epithelial cells possibly due to decreased tear film thickness. Other possible explanations include insulating the cornea from the hypo-osmotic shift that occurs with sleep.