Selective reduction of the S cone electroretinogram in diabetes.

AIMS To determine whether the short wavelength sensitive (S) cone electroretinogram (ERG) is selectively altered in diabetic patients with and without retinopathy. METHODS Ganzfeld spectral flashes in the presence of bright white background illumination were used to elicit S cone ERGs is 15 non-retinopathic diabetics, 16 background retinopathic diabetics, and 16 age matched normal controls. RESULTS The amplitude of the S cone ERG b-wave was significantly reduced in both non-retinopathic and retinopathic diabetics. An action spectrum based on equal response criteria revealed a selective loss of S cone sensitivity in diabetics. However, no significant difference was observed in the long and middle wavelength sensitive cone ERG. CONCLUSIONS Diabetic patients showed selective reduction of the S cone ERG, which is thought to reflect changes in the outer retina.