Abstract
Purpose :
Retinal vascular reactivity (RVR), a potential indicator of vascular health, is often assessed using arterial and venous parameters. Assessing RVR at the capillary bed is desirable because it can provide information about the functionality of capillary pericytes and basement membrane, impacted earlier in Diabetes, with minimal interference from the vascular wall. We assessed RVR at the capillary bed of controls and subjects with diabetic retinopathy (DR) to explore potential utility of RVR as a biomarker for DR.
Methods :
Quantitative analysis was performed on swept-source OCT angiograms of 22 control eyes and 17 eyes with DR. The images for each subject were acquired under three gas non-rebreathing conditions: 100% O2, 5% CO2 gas mixture and room-air. The conditions represented hyperoxic, hypercapnic and baseline breathing respectively. OCTA morphometric measures: vessel area density (VAD), vessel skeletal density (VSD) and Vessel Diameter Index (VDI) were compared between the controls and subjects with DR using mixed-model ANOVA that adjusted for age. Significant gas, or interaction effects were followed by pairwise posthoc analysis.
Results :
The controls were younger than the subjects with DR with a mean(SD) age of 47(19) and 62(11) years respectively, t(36)=2.7, p=0.001. The OCTA images (Fig. 1) showed changes in the capillaries under the three experimental conditions. The mixed-model ANOVA of the VAD found a significant gas (F(2, 74)=31.18, p<0.001), group (F(1, 37)=7.8, p<0.008), and interaction effects (F(2, 74)=3.32, p=0.03). The posthoc pairwise comparisons (Fig. 2) found significant differences among all three conditions in the controls. In the subjects with DR, however, there were significant differences in VAD between hyperoxic and room-air, and between hyperoxic and hypercapnic conditions, but not between hypercapnic and room-air conditions. The VSD and VDI results were comparable to the VAD.
Conclusions :
The vascular retina in subjects with DR preferentially reacted to hyperoxic but not hypercapnic perturbation, while the controls reacted to both forms of perturbation. This difference in RVR can be harnessed to enhance the use of OCTA for diagnosing and understanding the pathophysiology DR.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.