Inner Retinal Oxygen Delivery and Metabolism in Non-proliferative and Proliferative Diabetic Retinopathy

Abstract

Purpose : Hypoxia has a significant role in the pathogenesis of diabetic retinopathy (DR). Previous studies have reported increased retinal venous oxygen saturation and decreased retinal blood flow and metabolism with increasing DR severity in non-proliferative DR (NPDR). There is no report on alterations in retinal oxygen delivery (DO₂) and metabolism (MO₂) in proliferative DR (PDR). The purpose of the current study was to test the hypothesis that DO₂ and MO₂ are altered in patients with NPDR and PDR.

Methods : A total of 111 subjects participated in the study, and one eye of each subject was evaluated. The eyes were categorized into four DR groups: non-diabetic (ND; N=44), mild NPDR (N=30), moderate to severe NPDR (N=22), and PDR (N=15). Retinal vascular oxygen saturation (SO₂) and total retinal blood flow (TRBF) measurements were obtained using our oximetry system and Doppler optical coherence tomography techniques, respectively. DO₂ and MO₂ were calculated from SO₂ and TRBF. Categorical variables (age, sex, and race) were compared using the X² test. A univariate analysis was used to test for associations of DR groups with DO₂ and MO₂. Age, sex, and race were included in the model to control for these factors.

Results : Age, sex, and race were not significantly different among DR groups (p≥0.13). There was a significant association between DR groups and DO₂ (p=0.003). DO₂ was decreased from ND (8.6 ± 2.9µLO₂/min) to moderate to severe NPDR (7.9 ± 3.1µLO₂/min), mild NPDR (7.5 ± 3.0µLO₂/min), and PDR (5.0 ± 1.7µLO₂/min) groups. The mean value of DO₂ was lower in PDR as compared to ND (p<0.001), mild NPDR (p=0.004), and moderate to severe NPDR (p=0.002) groups. In addition, there was an association between DR groups and MO₂ (p=0.03). MO₂ was also decreased from ND (3.3 ± 1.1µLO₂/min) to moderate to severe NPDR (2.8 ± 1.5µLO₂/min), mild NPDR (2.7 ± 1.5µLO₂/min), and PDR (1.9 ± 0.8µLO₂/min) groups. The mean value of MO₂ was lower in PDR as compared to ND (p=0.003), mild NPDR, and moderate to severe NPDR groups (p=0.03).

Conclusions : The findings demonstrated reductions in both DO₂ and MO₂ in PDR compared to non-diabetic, mild, and moderate to severe NPDR subjects.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.