Transmission and scanning electron microscopic studies on endothelial cells in macular corneal dystrophy

Macular corneal dystrophy of both eyes in a 50-year-old man was studied by light microscopy and transmission and scanning electron microscopies. The endothelial cells contained empty vacuoles and numerous granules stained with alcian blue and periodic acid fuchsin. The endothelial cells were thin, especially at the guttata excrescences of the Descemet's membrane. Transmission electron microscopy revealed two types of vacuoles in the endothelium. The first type, which has been reported before, contained fine fibrillar material. The second type, described for the first time in this paper, was larger in size than the first type, and contained mostly amorphous material which appeared at the same electron density as the empty space of the anterior chamber, while a small amount of fibro-membranous materials were occasionally seen in the vacuoles. The second type of vacuoles sometimes appeared to be flattened. Cytoplasmic organelles of the endothelial cells and endothelial junctions were normal. Endothelial cells at the guttata excrescences were thin and contained only fine filaments. Slight depressions were observed on the endothelial surface facing the anterior chamber. Scanning electron microscopy of the endothelium showed an irregular surface which was composed of craters, nodules and pits. The cytoplasmic membrane of the endothelial cells at the top of the craters were continuous with that at the bottom of the craters. Marginal folds of the endothelial cells were obscure. Vacuoles of the first type were identical to those seen in the keratocytes of this disease. The second type of vacuoles and the guttata excrescences of the Descemet's membrane were thought to represent the craters and nodules on the endothelial surface.