Evaluation of retinal function and flicker light-induced retinal vascular response in normotensive patients with diabetes without retinopathy.

PURPOSE To correlate retinal function with vascular response to flicker light in normotensive patients with diabetes without diabetic retinopathy (DR). METHODS Twenty-eight normotensive patients with diabetes (11 with type 1, 17 with type 2) without DR and 28 sex- and age-matched healthy control subjects underwent color vision and contrast sensitivity testing, pattern, full-field, and multifocal electroretinography, and evaluation of the vascular response to flicker light with the dynamic vessel analyzer. RESULTS In the patients with diabetes, electroretinogram (ERG) pattern responses, b-wave in the scotopic bright flash ERG, a-wave and b-wave in the photopic single-flash ERG, and oscillatory potential responses were significantly impaired compared with those in control subjects. Vascular response to flicker light was also impaired in patients with diabetes compared with controls. In the whole population, correlations were found between flicker light-induced arterial retinal vasodilation and the amplitude and implicit time of the N95 wave of pattern ERG (r = -0.27, P = 0.047 and r = -0.35, P = 0.008, respectively), the b-wave implicit time of rod ERG (r = -0.36; P = 0.01) and the oscillatory potentials (r = 0.4; P = 0.003), suggesting that impairment of the vascular response to flicker light may reflect inner retinal neural impairment. However, no correlation between these factors was found when only patients with diabetes were considered. CONCLUSIONS In patients with diabetes, neural and neurovascular dysfunctions both precede the onset of clinically detectable DR. To which extent these abnormalities are related to each other remains to be determined. (ClinicalTrials.gov number, NCT00839150.)