Biophysical aspects of epithelial adhesion to stroma.

The affinity of various corneal boundary surfaces, such as mucus-coated epithelium, demucinized epithelium, denuded basement membrane, and keratectomized cornea, to water and hydrophobic liquids was determined by contact angle goniometry on enucleated rabbit eyes. The mucus-coated surface and the bare stromal surface without the basement membrane were found to be more hydrophilic than the surfaces of the epithelium and the basement membrane. If at least one of the surfaces forming a joint boundary is hydrophilic, then conditions become favorable for the accumulation of water at the interface, forming a weak boundary layer that is detrimental to adhesion, due to its low shear resistance. Thus, even in a normal eye, mucus does not adhere strongly to the epithelium; when the basement membrane is damaged or absent, the epithelium does not adhere well to the stroma. External dehydrating factors such as hyperosmotic conditions favor adhesion, whereas edematic conditions have an adhesive (adhesion-decreasing) effect. Experimental ophthalmic solutions containing macromolecules at hyperosmotic concentrations may demonstrate a therapeutic effect when applied to eyes with recurrent epithelial erosion or other epithelial trauma.