Impaired Layer Specific Retinal Vascular Reactivity Among Diabetic Subjects

Abstract

Purpose : To investigate layer specific retinal vascular reactivity in diabetic subjects using swept-source OCTA.

Methods : This was a single-armed, prospective, observational study. A previously described (Ashimatey et al., IOVS 2019) non-rebreathing apparatus was used to deliver room air, a 5% CO₂ gas mixture, and 100% O₂ to controls (N=30) and diabetics (N=22) with simultaneous acquisition of 3x3 mm² swept-source OCTA images (PlexElite^TM, Carl Zeiss Meditec, Dublin, CA) centered on the fovea. Vessel skeleton density (VSD) metric was calculated for each condition for the segmented superficial retinal layer (SRL) and deep retinal layer (DRL) as previously described (Kim et al., IOVS 2016). Analyses were performed using averaged OCTA images derived from 2 or more scans for each subject. Data analysis was performed using mixed factorial analysis of covariance (ANCOVA) stratified by diabetic stats. All models were adjusted for age, gender, and hypertension.

Results : There is a significant effect of retinal layer (p<0.001) and gas-layer interactions on VSD for both non-diabetics (p=0.001) and diabetics (p<0.001). There is a significant effect of gas on VSD among non-diabetics (p<0.001). This difference is driven by both change in the SRL (p<0.001) and DRL (p<0.001). Within each layer there is a significantly higher VSD during room air and CO₂ conditions than during O₂ (both p<0.017). Among diabetics, there is a borderline significant effect of gas on VSD regardless of layer (p=0.04). The magnitude of this effect is less than in non-diabetics and this effect is driven primarily by lower VSD in the DRL between gas conditions (p<0.007). Specifically, in the DRL the VSD is significantly lower under O₂ conditions compared to room air conditions (p<0.017). The magnitude of change in VSD between gas conditions by layer is exhibited in Figure 1. Similar results were obtained when only single images were used for the analysis.

Conclusions : Impairment in RVR in diabetic subjects is driven largely by a decrease in the robustness of the response to O₂ in the SRL as well as almost complete attenuation of CO₂ in all layers. These layer and gas specific impairments in diabetics may play a useful role in disease detection.

This is a 2020 ARVO Annual Meeting abstract.

 

Fig 1: Magnitude of change of VSD between gas conditions by layer for controls and diabetics (DM) with or without retinopathy (DR). Asterisk denotes significant differences in reactivity between layers by paired t-test.