Temporal Aspects of the Electroretinogram in Diabetic Retinopathy

• We measured the temporal aspects of several components of the electroretinogram in 72 patients with diabetes and 29 control subjects. The measurements consisted of the implicit times of the a wave and oscillatory potentials elicited by a bright-flash stimulus and the implicit time of the b wave in response to a 30-Hz flickering light. The a wave and first three oscillatory potential nodes were significantly delayed in the patients with diabetes compared with the controls; among the diabetics, a significant increase in the delay of the second and third nodes occurred as a function of increasing retinopathy severity. Similarly, the 30-Hz flicker implicit times (with and without a background light) were significantly delayed in patients with diabetes, and the magnitude of the delay increased with increasing retinopathy severity. The correlations of 30-Hz flicker implicit times with retinopathy severity were significant for retinopathy level graded in color fundus photographs as well as for retinal capillary nonperfusion and leakage graded in fluorescein angiograms. A comparison of 30-Hz flicker implicit times in 15 patients with one eye treated with panretinal laser photocoagulation and the other eye untreated (treatment was randomly assigned) showed a significant delay in the treated eyes compared with the untreated eyes (paired eye comparison). This suggests that panretinal laser photocoagulation induces a further delay in the b-wave implicit times of eyes treated for diabetic retinopathy.