Meesmann's corneal dystrophy: ultrastructural features.

Ultrastructural studies were done on a cornea obtained at the time of lamellar keratoplasty from a patient with the clinical diagnosis of Meesmann's corneal dystrophy. Light microscopy showed in the corneal epithelium the typical tiny cysts containing cellular debris and a homogeneous substance that reacted with periodic acid and Schiff's reagent and stained with Hale's colloidal iron; as well, the basement membrane was markedly thickened. Electron microscopy revealed that the cysts had a corrugated or microvillous wall, consistent with acantholysis. The epithelial cells were rich in glycogen, and many contained the peculiar substance described by others in Meesmann's corneal dystrophy. This substance appeared to be derived from the tonofilaments and was in close relation to the desmosomes. The thick basement membrane showed secondary changes, with one thick zone that was rich in collagen fibrils mimicking abnormal anchoring fibrils and one thin zone that was poor in fibrils but had frequent intercalated fibroblasts and probably represented a repair phenomenon. There was no apparent modification of Bowman's layer or the superficial stroma.