We evaluated 164 eyes of 87 patients with diabetes mellitus compared with 50 eyes from 25 healthy subjects as the control group. We compared 87 patients with diabetes mellitus (164 eyes) in relation to their duration of diabetes, fundus findings, visual acuity, and color vision defects. In all patients, color vision defects were determined using the Farnsworth-Munsell 100-hue test, and the total error score was established on the basis of age norms from subjects without diabetes. No color vision defect was detected in the control group. In the diabetic group, fundus degeneration and color vision defects were observed and correlated with the duration of diabetes. The dominant color defect was of the blue-yellow type.