Retinal Vasculature of Different Diameters and Plexuses Exhibit Distinct Vulnerability to Varying Stages of Diabetic Retinopathy

Abstract

Purpose : We studied the impact of different stages of diabetic retinopathy (DR) on the vessel densities (VD) of different-sized vessels in the retinal superficial & deep vascular complexes (SVC and DVC) using optical coherence tomography angiography (OCTA) and analyzed the images via deep learning.

Methods : In this retrospective, cross-sectional study, 854 eyes of 854 subjects were divided into 5 groups: healthy controls (555 eyes), diabetics with no DR (90 eyes), early DR (mild and moderate non-proliferative diabetic retinopathy (NPDR)) (96 eyes), late DR (severe NPDR) (42 eyes) and proliferative DR (PDR) (71 eyes). Only dry maculae were included. OCTA imaging was done using the RTVue Avanti device (Optovue Inc, USA) and the machine-segmented 3x3 mm² macular SVC & DVC scans were obtained. VD measurements were extracted using a two-step pipeline. We employed a nnU-Net neural network combined with transfer learning from artificial vessel images to segment the vasculature in fine detail (Fig.1). The radius of each vessel was determined using the Voreen software. VD for each plexus was calculated and stratified by vessel diameter (<10μm, 10-20μm, >20μm). Non-parametric tests were used to assess the differences in VD between groups. P-values were adjusted for multiple comparisons.

Results : Overall VD measurements were statistically significantly different between the groups in both the SVC & DVC with a progressively decreasing trend with increasing DR severity (p <0.001 in both). The largest percentage difference between the healthy and no DR groups was in the <10μm vessels of the SVC (13.9% lower in no DR, p <0.001). Significant decreases in <10μm vessels of both the SVC and DVC were seen between no DR to early NPDR, and early to late NPDR, however the 10-20μm vessels only showed significant differences in the DVC, but not the SVC (10.2 & 16.5% respectively, p <0.001 in both).

Conclusions : Eyes with no DR in people with diabetes exhibit profound decline in the density of the smallest vessels of the SVC compared to healthy controls. These vessels in the SVC and DVC continue to decrease with increasing severity level of DR. However, larger vessels of 10-20μm only show significant differences in the DVC, but not the SVC. Our findings suggest the possibility of a distinct vulnerability of retinal vessels of different diameters and vascular plexuses to varying stages of DR.

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