[Microscopic study of the corneal epithelium based on intracellular turnover of fluorogenic substrates]

The methods presently available for examination of the corneal epithelium by use of the ophthalmic slit lamp are more or less restricted to the detection and diagnosis of significant lesions and the morphological results of pathologic processes in the epithelial layer at relatively low magnification and optical resolution. There is an increasing demand, however, for early detection of initial damaging effects to the corneal epithelium by testing simple specific reactions at cell level. Fluorescein microscopy of the intracellular turnover of fluorogenic substrates may become a valuable methodological basis for such an examination of the corneal epithelium. Orienting experimental investigations into the uptake and turnover of fluorescein-di-acetate (FDA) by the epithelial cells of the rabbit cornea after its exposure to isotonic 10(-5) molar FDA solution, using an endothelial specular microscope and an image intensifier TV camera, demonstrate that this principle permits a superior microscopic presentation not only of the cellular epithelial structure in general, but also of locally damaged areas of the epithelium immediately after their exposure to damaging chemical agents, in particular to substances affecting cell membranes.