Electroretinographic evaluation of diabetic retinopathy: sensitivity of amplitude and time of response.

Amplitude and delay of oscillatory potentials were studied in the electroretinograms (ERGs) of patients with diabetes to see which was the more sensitive for evaluating diabetic retinopathy. Loss of amplitude was more sensitive in identifying eyes with early stages of retinopathy, in which funduscopic evidence of retinopathy was still absent, whereas delay of response was more sensitive in grading eyes with later stages. With cases classified according to stage of retinopathy, loss of amplitude and delay of response, a theoretic curve of the electrophysiologic time-course of diabetic retinopathy was drawn. The curve showed that amplitude can distinguish normal from preretinopathic eyes, that with a loss of amplitude of less than 50% no retinopathy will be found ophthalmoscopically, and that with a delay of response greater than 8% the delay will correlate well with the stage of retinopathy.