Retinal Oxygen Saturation is Altered in Diabetes

Abstract

Purpose: Retinal vessel oxygen saturation (SO2) is altered in persons with diabetes compared to healthy subjects. However, it is unclear whether these changes are associated with the presence of diabetes independent of traditional parameters of systemic control, such as HbA1c and blood pressure. The aim of this study was to determine if the presence of diabetes is independently associated with retinal oximetry measures (arteriolar SO2; venular SO2; and the arterio-venous [A-V] difference).

Methods: Retinal oxygen saturation levels were assessed using the oximetry module of the Vesselmap system in 100 eyes of 50 healthy subjects and 92 eyes of 58 patients with diabetes aged 18 to 84 years. Aside from diabetic retinopathy, all participants had no other signs of retinal diseases. Generalized estimating equation models were used to estimate the associations between presence of diabetes and the arteriolar SO2; venular SO2; and the A-V difference, while adjusting for systemic and ocular parameters (age; gender; retinal capillary flow; HbA1c; triglyceride; total cholesterol; systolic and diastolic blood pressure [SBP and DBP, respectively]; anti-hypertensive medication use; intraocular pressure; and smoking status).

Results: In unadjusted analyses, presence of diabetes was found to be associated with all three measures of retinal oximetry. In models adjusting for age, gender, and parameters significantly associated with arteriolar SO2 in unadjusted analyses (anti-hypertensive medication use, HbA1c and SBP); presence of diabetes was no longer associated with arteriolar SO2 (β = 0.71, 95% CI: -2.78 to 4.20). In contrast, diabetes (β = 5.14, 95% CI: 0.97 to 9.32) remained significantly and independently associated with venular SO2 after adjustment for age, gender, anti-hypertensive medication use, HbA1c and SBP. Similarly, the presence of diabetes was significantly associated with the A-V difference (β = -3.08, 95% CI: -5.53 to -0.64), independent of age, gender, anti-hypertensive medication use, HbA1c, SBP and total cholesterol.

Conclusions: The presence of diabetes is independently associated with increased venular SO2 and decreased A-V difference, suggesting a possible reduction in oxygen consumption in the diabetic retina. Our results add to previous evidence which have shown compromised retinal metabolism in diabetes.

Keywords: 499 diabetic retinopathy • 635 oxygen • 688 retina