OCT angiography fractal analysis-based quantification of macular vascular density in branch retinal vein occlusion eyes.

OBJECTIVE

To compare the macular vascular density in branch retinal vein occlusion (BRVO) versus normals on optical coherence tomography angiography (OCTA) using fractal analysis and to describe the factors bearing on final visual outcomes.

PARTICIPANTS

This study is a retrospective observational comparative case series. Diagnosed cases of unilateral BRVO that underwent treatment and resolved were included. The other eye served as control.

METHODS

OCTA images of the cases and control eyes were analyzed using fractal dimension on the MATLAB platform. Vascular density fraction was calculated for each eye for both the retinal vascular layers. Images were cleaned of artifacts before processing. Total vascular density in normals was compared with those with branch retinal vein occlusion.

RESULTS

116 eyes were normal and 98 had BRVO. The mean age of the normals was 56.63 ± 12.5 years and 58.41 ± 10.7 years of the BRVO group (p = 0.6). Superficial vascular density fraction was noted as 0.29 ± 0.08 (95% CI 0.27-0.31) and 0.25 ± 0.1 (95% CI 0.23-0.27) respectively (p = 0.003). Deep vascular density was noted as 0.39 ± 0.11 (95% CI 0.32-0.41) and 0.14 ± 0.09 (95% CI 0.12-0.19) (p < 0.0001). Pearson's correlation coefficient was -0.4 (p = 0.04) for the effect of age on vascularity, -0.53 (p = 0.001) for the effect of vascularity on final vision, and 0.35 (p = 0.09) for the effect of duration of symptoms on final vision.

CONCLUSIONS

In BRVO vascular density decreases significantly in the deeper retinal layer. Vision deficit correlates to increased age, duration of symptoms, and greater vascularity loss.