Superficial capillary perfusion on optical coherence tomography angiography differentiates moderate and severe nonproliferative diabetic retinopathy

Abstract

Purpose To identify objective optical coherence tomography angiography (OCTA) parameters that characterize the spectrum of non-proliferative diabetic retinopathy (NPDR), especially those that distinguish moderate from severe NPDR. Methods Sixty eyes of 60 patients with treatment-naïve NPDR (mild: 21, moderate: 21, severe: 18), 23 eyes with diabetes and no retinopathy, and 24 healthy control eyes were enrolled. OCTA slabs were segmented into superficial (SCP), middle (MCP), and deep capillary plexus (DCP) and thresholded by a new method based on DCP skeletonized vessel length. The foveal avascular zone (FAZ) area, parafoveal vessel density (VD), and adjusted flow index (AFI) from all three capillary layers and the vessel length density (VLD) of the SCP were compared between each severity group, after adjusting for age and image quality. Results All vessel density markers decreased with increasing severity of NPDR. SCP VD and VLD demonstrated significant differences between eyes with diabetes with no retinopathy and mild NPDR ( p = 0.001 and p < 0.001, respectively), as well as between moderate vs. severe NPDR ( p = 0.004 and p = 0.009, respectively). MCP VD significantly decreased between moderate and severe NPDR ( p = 0.01). AFI significantly increased in the SCP and showed a decreasing trend in the MCP and DCP with increasing NPDR severity. Conclusions Changes in the SCP VD, SCP VLD, and MCP VD can distinguish severe NPDR from lower-risk stages. SCP changes may be more reliable due to their lower susceptibility to noise and projection artifacts. Thresholding OCTA images based on DCP skeletonized vessel length showed less variability in moderate and severe NPDR. Additional studies are warranted to validate this new thresholding method.

Review of OCT Angiography Findings in Diabetic Retinopathy: Insights and Perspectives

“…As corroborated extensively in the literature, FAZ size increases with the progression of DR (Figure 4) [71,74,78,[100][101][102][103]. Several of these studies evaluated the FAZ of the SCP and DCP separately.…”

“…Analysis of the MCP as a distinct vascular layer opened a window of opportunity to understand how DR may have spatially unique impacts. In general, studies have found that trends within the MCP mirrored those occurring at the SCP and DCP; as DR severity increased, VD and VLD both decreased [76][77][78]. Interestingly though, DR severity had different effects on the vascular layers.…”

“…In all three capillary plexuses (SCP, MCP, and DCP), decreasing VD and VLD have both been found to be associated with increasing severity of DR (Figure 3) [71][72][73][74][75][76][77][78]. Furthermore, diminishing VD has been linked to poorer visual acuity in patients with DR, heightening the functional significance these parameters may bear out [79,80].…”

Retinal Vascularization Abnormalities Studied by Optical Coherence Tomography Angiography (OCTA) in Type 2 Diabetic Patients with Moderate Diabetic Retinopathy

“…However, Ong et al [ 40 ] described the utility of VD evaluation, the FAZ and the vessel length density at the SCP to distinguish healthy subjects and the different stages of nonproliferative DR (NPDR). They suggested that SCP changes are more reliable due to the lower noise and artefacts in OCTA acquisition.…”

Widefield Optical Coherence Tomography Angiography in Diabetic Retinopathy

“…The introduction of projection-resolved (PR) OCTA algorithms [ 36 , 37 ] and 3D visualization [ 38 ] systems has increased the quality of depth-resolved OCTA scans. Indeed, while in 2D reconstructions, retinal layers are segmented and reconstructed by two topographic axes (i.e., x and y ), volume-rendered OCTA reconstructions integrate structural and angiographic data to create 3D images.…”