An electrophysiological investigation of visual function in juvenile insulin-dependent diabetes mellitus

Current diabetes research is directed at preventing secondary complications such as diabetic retinopathy (DR) that can have devastating effects on vision. Diagnosis of DR is traditionally dependent on visible alterations of retinal vasculature. However, the detection of functional disorders, likely occurring before observable changes in structure, may provide advanced warning of impending DR. We examined the neural function of the retina by electroretinograms (ERG's) and the macular-cortical pathways by visual evoked potentials (VEP's) in 30 insulin-controlled juvenile diabetics and an age-and sex-matched group of nondiabetics. The average duration of diabetes in the test group with normal retinal vasculature was 5.6 +/- 4.6 years. Results showed small but measurable differences in the amplitude and timing characteristics of retinal and cortical potentials for the test and control groups. The most surprising findings related to shorter response times for the "b" wave of the photopic ERG, larger amplitude oscillatory potentials, and larger steady-state VEP's. These may be the earliest signs of increased segmental blood flow by vascular autoregulatory mechanisms to compensate for generalized hypoxia. Longitudinal studies are required to determine the physiological significance of our findings and the prognostic value of evoked potentials in diabetes.