Widefield OCT Angiography and Euclidian Distance Analysis of Microvascular Deficits in Glaucomatous Eyes

To evaluate superficial microvascular deficits of glaucomatous eyes with widefield OCT angiography (OCTA) and Euclidian distance (ED) analysis.

Cross-sectional study.

Swept-source OCTA (SS-OCTA) images of healthy and glaucomatous eyes.

Twelve-by-twelve mm scans of healthy and glaucomatous eyes were acquired with SS-OCTA (PLEX Elite 9000, ZEISS). The en face images of the superficial retina segmentation were exported and analyzed with ImageJ software. A fixed threshold that predicted the size of the foveal avascular zone was used to generate binarized images with vascular (white) or deficient (black) pixels. Four vascular parameters were measured within a macula-centered 9 × 10.8 mm ellipse: vascular density (VD), average ED (ED_avg), maximum ED (ED_max), and nonperfusion density (NPD). Euclidian distance values were visualized with a heatmap color scale. The vascular parameters were compared between healthy and glaucomatous eyes (Student t-test). Person coefficients were calculated to test correlations between the vascular parameters and retinal nerve fiber layer (RNFL) thickness, macular ganglion cell and inner plexiform layer (GCIPL) thickness, and visual field mean deviation in glaucomatous eyes. P < 0.05 was considered significant.

Vascular density, ED_avg, ED_max, and NPD RESULTS: Forty glaucomatous and twenty-five healthy eyes were included. Vascular density (fraction) was 0.442 ± 0.029 vs 0.320 ± 0.072 (P < 0.001), ED_avg (μm) was 17.37 ± 0.55 vs 32.62 ± 9.54 (P < 0.001), ED_max (μm) was 153.7 ± 49.1 vs 248.5 ± 156.6 (P = 0.005), and NPD (%) was 0.97 ± 0.82 vs 7.09 ± 5.99 (P < 0.001) in healthy vs glaucomatous eyes. Vascular density, ED, and NPD were better in optic nerve head sectors than in temporal macula and retinal periphery sectors in both groups, but were worse in the glaucoma group across all sectors of the ellipse (P < 0.01 for all sectors). Microvascular deficits in glaucomatous eyes often exceeded structural and functional glaucomatous damage, and there was modest correlation between the vascular and structural or functional parameters. Pearson ρ of the correlation with average RNFL and GCIPL were highest for VD (ρ = 0.46, P = 0.002 and ρ = -0.49, P = 0.001, respectively) and lowest for ED_max (ρ = -0.19, P = 0.24 and ρ = -0.23, P = 0.16, respectively).

Vascular density, ED, and NPD were worse in glaucomatous compared to healthy eyes throughout the widefield OCTA image. High ED and NPD values accentuate regions of inadequate perfusion.

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