Type 1 and type 2 diabetic patients with no diabetic retinopathy and no hypertension were compared with sex and age-matched control subjects. Color vision was tested with the desaturated LANTHONY 15-Hue test. Contrast sensitivity was assessed with the Pelli-Robson contrast sensitivity test. Pattern-electroretinogram, Ganzfeld full-field electroretinogram and multifocal electroretinogram were recorded according to the International Society for Clinical Electrophysiology of Vision (ISCEV). Flicker-induced vasodilatation in retinal arteries and veins was assessed using the Dynamic Vessel Analyzer.