Specular microscopy was employed to study the corneal epithelium of 20 keratoconus patients (17 male, 3 female, average age 23.9 +/- 6.6 years). The patients were divided into three groups based on the severity of the keratoconus; early, intermediate, and advanced. Initially, epithelial changes were limited to enlargement of the superficial cells. As the disease progressed, elongated cells became prominent. Irregularly configurated and nucleated epithelial cells were observed in all cases. Morphomeric analysis showed that the mean area of the corneal epithelial cells was 906 +/- 203 microns 2 in the early stage, 1,416 +/- 521 microns 2 in the intermediate stage, and 1,641 +/- 372 microns 2 in the advanced stage. The shape factor was 0.32 +/- 0.05, 0.76 +/- 0.22, and 0.81 +/- 0.17, respectively. Controls were chronic wearers of hard contact lenses without corneal pathology. Analysis of their epithelium revealed no abnormalities. This finding suggests that the epithelial changes observed in keratoconus are not due to the wearing of contact lenses, but rather to the disease itself.