It has long been known that bits of cornea when placed in distilled water, normal saline, or even hypertonic saline tend to swell to many times their normal thickness. These observations plus the recognition that hydration of the cornea may occur in various clinical situations have spurred a number of studies on the mechanism by which the cornea normally maintains its hydration in vivo.
Harris JE. Current Thoughts on the Maintenance of Corneal Hydration in Vivo. Arch Ophthalmol. 1967;78(2):126-132. doi:10.1001/archopht.1967.00980030128004