The aim of the present study was to assess retinal oxygen metabolism in patients with type II diabetes and different stages of non-proliferative diabetic retinopathy (DR) and compare these findings to healthy controls. For this purpose, 67 patients with type II diabetes and 20 healthy controls were included in this cross-sectional study. 34 patients had no, 15 had mild and 18 had moderate to severe DR. Retinal oxygen saturation in arteries and veins was measured using the oxygen module of the Retinal Vessel Analyzer (RVA). Total retinal blood flow (TFBF) was measured using a custombuilt Doppler optical coherence tomography system. Retinal oxygen extraction was calculated out of retinal oxygen saturation and TRBF. Arteriovenous difference in oxygen saturation was highest in healthy subjects (34.9±7.5%), followed by patients with no DR (32.5±6.3%) and moderate to severe DR (30.3±6.5%). The lowest values were found in patients with mild DR (27.3±8.0%, p=0.010 vs. healthy subjects). TRBF tended to be higher in patients with no DR (40.1±9.2µl/min) and mild DR (41.8±15.0µl/min) compared to healthy subjects (37.2±5.7µl/min) and patients with moderate to severe DR (34.6±10.4µl/min). Retinal oxygen extraction was the highest in healthy subjects (2.24±0.57µl O2/min), followed by patients with no DR (2.14±0.6µl O2/min), patients with mild DR (1.90±0.77µl O2/min) and patients with moderate to severe DR (1.78±0.57µl O2/min, p=0.040 vs. healthy subjects). These results indicate that retinal oxygen metabolism is altered in patients with type II diabetes. Further, retinal oxygen extraction decreases with increasing severity of DR.

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