Inner retinal oxygen delivery and metabolism in progressive stages of diabetic retinopathy.

Previous studies have reported increased retinal venous oxygen saturation and decreased retinal blood flow and oxygen metabolism in non-proliferative diabetic retinopathy (NPDR). The current study aimed to determine alterations in both inner retinal oxygen delivery (DO) and metabolism (MO) in proliferative DR (PDR) as well as at stages of NPDR. A total of 123 subjects participated in the study and were categorized into five groups: non-diabetic control (N = 32), diabetic with no diabetic retinopathy (NDR, N = 34), mild NPDR (N = 31), moderate to severe NPDR (N = 17), or PDR (N = 9). Multi-modal imaging was performed to measure oxygen saturation and blood flow, which were used for derivation of DO and MO. There were significant associations of groups with DO and MO. DO was lower in PDR and not significantly different in NDR and NPDR stages as compared to the non-diabetic control group. MO was decreased in PDR and moderate to severe NPDR as compared to the control group, and not significantly reduced in NDR and mild NPDR. The findings demonstrate reductions in both DO and MO in PDR and MO in moderate to severe NPDR, suggesting their potential as biomarkers for monitoring progression and treatment of DR.