Electrophysiological measures of dysfunction in early-stage diabetic retinopathy: No correlation between cone phototransduction and oscillatory potential abnormalities

Purpose To define the relationship between abnormalities in the activation phase of cone phototransduction and the oscillatory potentials (OPs) of the light-adapted electroretinogram in diabetics who have mild or no retinopathy. Methods Subjects included 20 non-diabetic controls and 40 type-2 diabetics (20 had no clinically apparent diabetic retinopathy [NDR] and 20 had mild nonproliferative DR). Single flash responses for a series of stimulus retinal illuminances were measured under light-adapted conditions using conventional techniques. The a-waves of the responses were fit with a delayed Gaussian model to derive R mp3 (maximum amplitude of the massed photoreceptor response) and S (phototransduction sensitivity). OPs were extracted from the responses by conventional band-pass filtering. Results Analysis of variance (ANVOA) indicated that both diabetic groups had significant OP amplitude and S reductions compared to the controls, whereas R mp3 did not differ significantly among the groups. Although log OP amplitude and log R mp3 were significantly correlated for the control subjects for each flash retinal illuminance (all r > 0.49, p