Shifts in retinal vessel diameter and oxygen saturation in Chinese type 2 diabetes mellitus patients

Background: The aim of this study was to analyze the shifts in retinal vessel diameter and oxygen saturation in diabetic patients with and without diabetic retinopathy (DR), as well as to assess the association between diabetes duration and either vessel diameter or oxygen saturation.

Methods: In total, 99 Type 2 DM patients were recruited for the study and were divided into three groups: DM with non-obvious retinopathy (DM, n = 29), non-proliferative diabetic retinopathy (NPDR, n = 40), and proliferative diabetic retinopathy (PDR, n = 30). In addition, 78 age-matched healthy individuals were chosen as the control. The diameter and oxygen saturation of the retinal vessels were analyzed using a noninvasive retinal oximeter, and then compared between the three groups and the normal control. Association analysis was applied to analyze the possible influencing factors, including the diameter and oxygen saturation of retinal vessels, on best corrected visual acuity BCVA, as well as the relationship between diabetes duration and the oximetry values.

Results: All of the diabetic patients showed thinner arterioles, wider venules, and a smaller arteriolar-to-venular ratio (AVR) than the healthy individuals. The AVR results from the controls through to the PDR group were 0.81 ± 0.07, 0.78 ± 0.07, 0.76 ± 0.07 and 0.67 ± 0.07, respectively. Both the NPDR and PDR groups showed significantly smaller AVR than the control. All of the diabetic patients exhibited higher retinal vessel oxygen saturation than the healthy individuals. Among all of the oximetry values, AVR exhibited the most significant correlation with best corrected visual acuity (BCVA) (β = 1.533, P < 0.0001). An increased diabetes duration was associated with decreased arteriolar diameter (slope = -0.082 pixels/year, r (2) = 0.085, P = 0.004) and AVR (slope = -0.009/year, r (2) = 0.349, P < 0.001), and with increased venular diameter (slope = 0.104 pixels/year, r (2) = -0.109, P = 0.001).

Conclusions: In this Chinese population with type 2 DM, the thinner arterioles and wider venules point to microvascular dysfunction in DR. The increased oxygen saturation of the retinal vessels suggests that retinal oxygen metabolism is affected in diabetic retinopathy.