Aims: Keratoconus (KK) and Marginal Pellucid Degeneration (MPD) corneas were examined by electron microscope and these findings were compared to those in normal cornea.

Material and Methods: The corneas taken from cornea transplanted patients with 3 KK and 1 MPD were investigated. For transmission electron microscopy, these tissues were fixed in 2.5 % glutaraldehyde in phosphate buffer, post-fixed osmium tetroxide and routinely embedded and sectioned.

Results and Conclusions: When compared to those in the normal cornea, epithelial hyperplasia, thickening and edema in the KK corneas were observed. Basement membrane and Bowman's membrane were intact in the KK cornea. Vacuolization were observed in the cytoplasma of the epithelial basal cells of the MPD cornea. Interepilhelial space was increased. The cytoplasmic processes of the basal cell extended to Bowman's membrane and basal lamina was not found in this region. The thickness of Bowman's membrane was less than those of KK and normal corneas. Osmiophilic materials deposited in the Bowman's membrane and was broken in some regions.

Conclusions: It was thought that the degeneration in MPD cornea epithelial might be related to disorganization of the basal and Bowman's membranes.