THE CORNEA

Abstract

While comprehensive investigations of corneal permeability have been few, numerous isolated observations, employing a variety of technics and test substances and leading to diverse conclusions, have been reported. The subject was reviewed in 1937 by Gronvall 1 ; since this time 2 additional reports have appeared. 2 Until recently there has been wide acceptance of Leber's thesis that the epithelium and endothelium were impermeable to water, since the corneal stroma did not appear to imbibe fluid from the tears or the aqueous. At the same time, these membranes have been thought to be permeable to various dissolved substances, notably, the drugs commonly used in ophthalmologic practice. In recent times, Fischer 3 claimed to have shown that the cornea possesses a unidirectional permeability, similar to that previously hypothesized by Wertheimer for frog skin. According to Fischer's interpretation, water, sodium chloride, oxygen, alkaloids and acid dyes pass through the cornea from without inward,