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.