The corneal epithelia of phakic control (n = 13), aphakic control (n = 10), diabetic phakic (n = 10), and diabetic aphakic patients (n = 13) were surveyed under a wide-field specular microscope with a special contact lens. In control patients, the corneal epithelium showed relatively hexagonal cells, which we divided into three groups: bright cells, medium-bright cells, and dark cells. These epithelial cells displayed a smooth-surface configuration. In diabetic phakic patients, the epithelium seemed almost normal, with slightly more irregularity. In diabetic aphakic patients, the epithelium appeared larger. The cells were irregular and easy to distinguish from normal cells. Morphometric analysis showed that the mean cell areas of phakic control, aphakic control, diabetic phakic, and diabetic aphakic patients were 648 +/- 152, 643 +/- 125, 658 +/- 146, and 821 +/- 203 microns 2, respectively. The increase in the average cell area in diabetic aphakic patients was statistically significant. Although no apparent changes of the epithelium could be detected in the diabetic corneal epithelium under biomicroscopy, abnormalities that could be evaluated by specular microscopic images and morphometric analysis were observed.