Cellular and stromal edema are primary causes of decreased corneal transparency. This proposal is concerned with the physiology of the corneal epithelium and the relationship of its transport and permeability properties to epithelial and stormal hydration. Studies on the mechanisms and permeation pathways involved in the control of corneal hydration will be done in vitro with microelectrode recordings, radioactive tracer measurements, ion substitutions, pharmacological procedures, and mathematical modeling. In addition, the pattern of ion transport in the living animal will be studied. The influence of adrenergic innervation on epithelial transport will be studied. Neuroanatomical mapping procedures and combined neurophysiological and electrophysiological techniques will be used to assess the possibility of neural control of epithelial transport in vivo. The influence of epithelial transport and metabolism on corneal hydration will be studied with an automatic specular microscope. The thickness of the epithelium and stroma in response to applied potentials and in response to various agents will be measured. The basis for Sattler's Veil and the stromal edema that occurs with tear film anoxia will be examined in detail with thickness measurements, ultrastructural studies, biochemical analysis, and electrophysiological techniques.