Retinal oxygen metabolism and ocular blood flow in patients with diabetic retinopathy of varying severity

PURPOSE: To investigate blood flow velocity and pulse waveform parameters in the optic nerve head (ONH) and choroid and retinal oxygen metabolism in patients with diabetic retinopathy of varying severity. METHODS: Retrospective study of 72 patients was analysed. Eyes were categorized according to diabetic retinopathy (DR) severity into mild to moderate non-proliferative diabetic retinopathy (NPDR), severe NPDR and proliferative diabetic retinopathy (PDR). Retinal oximetry and laser speckle flowgraphy measurements were performed. RESULTS: Oxygen saturation in retinal arterioles was significantly higher in the PDR group compared to mild to moderate NPDR and severe NPDR groups (p = 0.006 for both comparisons). Oxygen saturation in retinal venules was significantly higher in the PDR group compared to mild to moderate NPDR (p = 0.016) and severe NPDR (p = 0.021) groups. In the ONH, mean blur rate (MBR)-vessel, representing blood flow velocity in the retinal vessels, and MBR-tissue, representing ONH blood flow velocity, were significantly lower in the PDR and severe NPDR groups compared to the mild to moderate NPDR group (p = 0.001; p = 0.041; p = 0.024; p = 0.028, respectively). Among the analysed pulse waveform parameters, flow acceleration index was significantly lower in the PDR group compared to the mild to moderate NPDR group (p = 0.006). CONCLUSIONS: Our results revealed a link between decreasing retinal and ONH blood flow velocities and increasing retinal arteriolar and venular oxygen saturation with increasing severity of DR.