Scanning electron microscopy of posterior polymorphous corneal dystrophy.

An 8 1/2-year-old girl had posterior polymorphous dystrophy that required keratoplasty. Similar lesions were found in the patient's mother, thus establishing the genetic trend of the disease. Scanning electron microscopy studies showed areas of endothelial cell degeneration and multiple depressions or pits. These seemed the most advanced and characteristic lesions of posterior polymorphous dystrophy. Transmission electron microscopy studies in areas adjacent to the pits showed an abnormally developed Descemet's membrane covered by two or more layers of elongated endothelial-like cells. Cells over Descemet's membrane seemed to deposit some Descemet's membrane material and both fine and coarse collagen fibrils. Cells had prominent mitochondria, normal endoplasmic reticulum, and desmosomal attachments. Cytoplasmic fibrils and microvilli were usually found in cells lining the anterior chamber. Specular microscopy and scanning electron microscopy recorded the image of only the innermost cells and these appeared as endothelium.