Spontaneous corneal degeneration in the rat.

Superficial punctate opacities were observed in the palpebral aperture region of the cornea of Sprague-Dawley and Wistar rats of both sexes and varying ages, but they were not observed in Lewis rats. Slit-lamp biomicroscopy localized the opacities in the subepithelial corneal stroma. Electron microscopy demonstrated 0.1-2.0 micron granules at the stromal-epithelial interface and in the adjacent stroma. Smaller granules, consisting of aggregates of amorphous granular material, were associated with bundles of filaments among collagen fibers. Larger granules were located adjacent to and sometimes straddle the epithelial basement membrane. The overlying epithelial cells were displaced, but otherwise appeared normal. Large granules consisted of layered dark and light electron dense rings and appeared in some instances to represent fusing of smaller granules. This rat keratopathy bears certain resemblance to granular dystrophy of man (Groenouw's Type I), but histochemically is dissimilar.