Overnight swelling of the living human cornea.

The overnight corneal swelling of nine subjects was measured with an electronic digital pachometer. Corneal thickness measurements were taken just before eye closure and after seven hours of sleep. Post-sleep recovery to original corneal thickness was followed. Results showed overnight corneal swelling to be about 4 1/2% with logarithmic recovery to baseline within the first hour after eye opening. Considerable variability in the magnitude of overnight swelling among human corneas was indicated. A review of current theories on the cause of overnight corneal swelling is also included.