Fig 1.
Demonstration of proposed deep capillary plexus (DCP) vessel length density (VLD)-based thresholding method.
(A) OCTA images in the DCP were thresholded using progressively increasing empiric values and skeletonized vessel length calculated. To identify the optimum threshold value, we fitted regression lines to the steep and plateaued regions of the curve, which we hypothesized would represent noise and signal, respectively, and calculated the threshold value as the intersection of both regression lines. (B) Comparison of original images (top row) with thresholded images (bottom row).
Table 1.
Demographic and image characteristics of study patients in each diabetic retinopathy severity group.
Fig 2.
Optical coherence tomography angiography capillary parameters plotted by diabetic retinopathy severity group.
Data were adjusted for age and image quality as assessed by Q-score. Columns from left to right: superficial (SCP), middle (MCP) and deep capillary plexus (DCP). Rows from top to bottom: mean values for parafoveal vessel density (VD), adjusted flow index (AFI), and vessel length density (VLD; only applicable for SCP), graphed continuously across healthy controls, diabetic eyes without retinopathy, mild NPDR, moderate NPDR, and severe NPDR. Foveal avascular zone area (FAZ) was calculated from the full retinal slab and is shown in the bottom right graph. Error bars represent 95% confidence intervals.
Table 2.
Association of optical coherence tomography angiography parameter values across non-proliferative diabetic retinopathy severity groups using Spearman correlations.
Table 3.
ANCOVA analysis of age- and Q-score-adjusted optical coherence tomography angiography capillary parameters by diabetic retinopathy severity group.
Table 4.
Pairwise comparisons of optical coherence tomography angiography capillary parameters between diabetic retinopathy severity groups using ANCOVA post-hoc analysis.
Fig 3.
Receiver operating characteristic curves for optical coherence tomography angiography parameters distinguishing severe from mild and moderate NPDR.
ROC analysis was performed to assess the ability of OCTA parameters to distinguish severe from mild and moderate NPDR. Superficial capillary plexus (SCP) vessel density (VD), vessel length density (VLD), and middle capillary plexus (MCP) VD were analyzed. AUC = area under curve; SN = sensitivity; SP = specificity.