Permeability of the limiting cell layers of the cornea in vivo

The permeability of the limiting cell layers of the cornea for solutions is of special interest with respect to the following points of view: 1) Protection against penetration of fluids from the tear film or aqueous into the stroma. 2) Nutrition of various corneal tissues from the tear film or from the aqueous humor. 3) Penetration of topically applied drugs into the anterior segment. 4) Side effects of drugs or surgery on the permeability of epithelial or endothelial layers. Fluoresceine sodium as a hydrophilic weak acid (MG 360) penetrates intercellulary through intact epithelium and endothelium. When topically applied the rise of fluoresceine concentration in the stroma depends on the permeability of the epithelium, whereas that in the aqueous may be controlled by the endothelial permeability. Small impairment of these cell layers leads already to increased permeabilities. This means that valuable information on the pathology of epithelial and endothelial layers may be obtained by quantitative clinical determination of the fluoresceine concentration by aid of sensitive fluorophotometers.