Water Permeability of the Human Cornea

An osmotically induced net volume flow of water was produced in human corneas by perfusion of hypertonic solutions over the epithelial surface. Corneal thinning resulted and was measured with a specially designed pachometer. The rate of thinning was used to calculate water permeability of human corneal epithelium and endothelium. Measurements on normal intact corneas indicated that endothelium was 3.4 times as permeable to bulk water flow as epithelium. In the presence of central cornea guttata, the corneal endothelium was found to be 6.3 times as permeable to water as the epithelium, or a twofold increase in water movement across the endothelium. Because normal corneal thickness was maintained in these corneas with early central cornea guttata, it was concluded that the endothelium must function as more than a simple barrier to water movement into the corneal stroma.