It has been proposed that a primary water pump across the cornea might provide the means by which the epithelial or endothelial metabolism keeps the cornea unswollen and transparent.1,2 Some data have been published which could be interpreted as evidence for a water pump acting across the endothelium.3 The cornea's permeability to water could also influence intraocular dynamics if there were a significant net transport of water into or out of the eye by active transport or by the normal hydrostatic pressure gradient.
Cogan and Kinsey measured water flux across the excised cat cornea using D2O as a tracer.4,5 No attempt was made in these studies to determine whether the corneas were alive and functioning. It is quite probable that their preparations were dead, and therefore, if an active corneal water transport exists, these corneas would not have exhibited it. Potts tried to measure the
DONN A, MILLER SL, MALLETT NM. Water Permeability of the Living Cornea. Arch Ophthalmol. 1963;70(4):515-521. doi:10.1001/archopht.1963.00960050517015