The flicker ERG and retinal blood flow relationship in diabetic patients without retinopathy

Purpose To evaluate the association between functional and hemodynamic alterations of the retina in diabetes mellitus (DM) without retinopathy (NDR). Methods 15 patients (63±6.3 years) with DM type II (duration 6±3.5years) and NDR, and 40 age matched controls were examined. Color Doppler Imaging (CDI) was conducted to visualize blood flow in ophthalmic artery (OA), central retinal artery (CRA), medial and lateral posterior ciliary arteries brevis (PCAB). Photopic and scotopic flicker ERGs (p-FERG and s-FERG) were recorded at 8.3, 10, 12, 30 Hz flickering. Results In NDR, the increase of the blood flow peak systolic velocity (V syst) and end diastolic velocity (Vdiast) was noted in AO. The most significant changes in blood flow were observed in CRA and PCAB. A reliable correlations were shown between Vdiast, the resistance index RI in CRA and insulin levels (r=0.64), serum C-peptide (r=0.60) and the index of insulin resistance IR (r=0.65); between Vdiast, RI in PCAB and insulin levels, the C-peptide level and IR (r=0.59, 0.56, 0.59, respectively). The amplitude of light and dark adapted FERG at 8.3-12 Hz declined in more than 60% eyes up to 69-80%. The p-FERGs at 24 and 30 Hz did not differ from the control; but we found a sharp increase in s-FERG (155.5±15.3 - 319.9±21.4% for 24 - 30 Hz respectively). Significant correlation was shown between the 10Hz-FERG amplitude (but not the 24Hz or 30Hz-FERG) and Vdiast in CRA and PCAB (r=0.51; r=0.50). Conclusion There is a significant relationship between the retina hemodynamics and physiological effects of insulin, leading to metabolic disorders. Signs of blood flow deficiency in CRA and PCAB in NDR correlated with an early alteration in the photoreceptor function.