Retinal oxgen metabolism under visual stimulation of neuronal activity in health and disease

Goal: To measure retinal vessel oxygen saturation in rest and under stimulation of neuronal activity by flicker light as well as vascular dilation upon flicker. Methods: 18 patients with non-proliferative diabetic retinopathy (mean age: 62.2±8.3 years), 41 patients with primary open angle glaucoma (64.0+12.8 years) and 40 control subjects (63.6+14 years) were investigated. Vessel diameters (central retinal arterial and venous equivalents – CRAE and CRVE) and oxygen saturation (SO2, dual – wavelength optical oximetry) were determined before and during luminance flicker stimulation (12.5 Hz, modulation depth: 1:20) for 90 s. Results: Flicker light increased CRAE, CRVE, and venous SO2 by 1.42%±3.72%, 2.80%*±2.70%, and 2.03%*±2.43% in diabetic patients as well as 4.98%*±6.23%, 8.94%*±5.26%, and 4.20%*±3.71% in the controls (*: p<0.05). This increase was significantly higher in the controls vs. patients for all parameters (t-test, p<0.05. In glaucoma, the increase of CRVE (3.7+3.3%, p=0.039) and venous SO2 (2.482+2.453%, p=0.029) was significantly lower than in controls. Conclusions: Combining SO2 and vessel diameter measurements with visual stimulation reveals pathologic alterations in retinal oxygen supply or consumption. Commercial interest