Quantitative microvascular analysis of retinal venous occlusions by spectral domain optical coherence tomography angiography

Abstract

Purpose: To quantitatively evaluate the retinal microvasculature in human subjects with retinal venous occlusions (RVO) using optical coherence tomography angiography (OCTA).

Design: Retrospective, cross-sectional, observational case series.

Participants: Sixty subjects (84 eyes) were included (20 BRVO, 14 CRVO, 24 unaffected fellow eyes, and 26 controls).

Methods: OCTA was performed on a prototype, spectral domain-OCTA system in the 3x3mm central macular region. Custom software was used to quantify morphology and density of retinal capillaries using four quantitative parameters. The vasculature of the segmented retinal layers and nonsegmented whole retina were analyzed.

Main outcome measures: Fractal dimension (FD), vessel density (VD), skeletal density (SD), and vessel diameter index (VDI) within the segmented retinal layers and nonsegmented whole retina vasculature.

Results: Nonsegmented analysis of RVO eyes demonstrated significantly lower FD (1.64±0.01 vs 1.715±0.002; p<0.001), VD (0.32±0.01 vs 0.432±0.002; p<0.001), and SD (0.073±0.004 vs 0.099±0.001; p<0.001) compared to controls. Compared to the fellow eye, FD, VD and SD were lower (p<0.001), and VDI was higher (p<0.001). FD, VD, and SD progressively decreased as the extent (or type) of RVO increased (control vs BRVO vs CRVO; p<0.001). In the unaffected fellow eye FD, VD and SD showed significant differences when compared to control eyes or affected RVO eyes (p<0.001).

Conclusions: Quantitative OCTA of the central 3x3mm macular region demonstrates significant differences in capillary density and morphology among subjects with BRVO and CRVO compared to controls or unaffected fellow eyes in all vascular layers. The unaffected fellow eyes also demonstrate significant differences when compared to controls. OCTA allows for noninvasive, layer-specific, quantitative evaluation of RVO-associated microvascular changes.

Fig 1. Representative OCTA images of fellow healthy eye and BRVO eye illustrating qualitative changes in capillary density and morphology.

(A) B-scan with purple dotted lines delineating the retinal vascular layers of interest in the healthy fellow eye of an RVO subject: Nonsegmented whole retina, NS-RL (a-d); Superficial retina layer, SRL (a-b); Deeper retina layer, DRL (b-c). Corresponding pseudocolored, depth-encoded OCTA map (B), binarized image (C), and skeletonized image (D) of the unaffected eye. (E-H) Corresponding images of the RVO eye, NS-RL analysis.

Fig 2. Comparison of quantitative OCTA parameters between RVO eyes and control eyes for nonsegmented layer analysis.

Row (A) bar charts illustrate the mean±SD of the quantitative OCTA parameters (Fractal Dimension, Vessel Density, Skeletal Density and Vessel Diameter Index) for eyes with retinal venous occlusion (RVO), the unaffected fellow eye (OE), and control eyes. Row (B) illustrates the same quantitative parameters for central (CRVO) and branch RVO (BRVO) compared to controls. Row (C) illustrates similarly for RVO eyes with and without macular edema. Multivariable linear regressions were performed and the GEE approach was used to control for age, gender, and between-eye correlation when appropriate. The asterisk(s) above the horizontal line indicates that the specified groups were statistically different. All other asterisks compare specified groups to controls. One asterisk, p<0.05; two asterisks, p<0.01; three asterisks, p<0.001.

Fig 3. Magnitude and direction of change in quantitative OCTA parameters among all study subjects using nonsegmented layer analysis.

Linear regression slope coefficient (β) indicating magnitude and direction of parameter difference, and corresponding confidence intervals. Abbreviations: RVO, retinal venous occlusion, OE, other (unaffected fellow) eye; CRVO, central retinal venous.