To evaluate the efficacy of optical coherence tomography angiography (OCTA) by measuring the foveal avascular zone (FAZ) area in patients with branch retinal vein occlusion (BRVO).

Thirty four eyes of 34 patients with BRVO were retrospectively reviewed. The area of the FAZ was calculated using fluorescein angiography (FAG) and OCTA. The FAZ area was divided into two groups according to the presence of macular edema, which was determined based on the central foveal thickness (300 µm), and then the measured areas were compared.

Pearson's correlation analysis revealed a significant positive correlation between FAG and the superficial capillary plexus (SCP) in OCTA with or without macular edema (r = 0.845, p = 0.001). However, there was not a significant correlation between FAG and the deep capillary plexus (DCP) in OCTA (r = 0.001, p = 0.996). In addition, the FAZ area measured by FAG and OCTA in the SCP showed a significant agreement between the two methods (intraclass correlation coefficient [ICC] = 0.916, p = 0.001). However, there was no significant relation found for the FAZ area between FAG and OCTA in the DCP (ICC = 0.001, p = 0.501).

In the patients with BRVO, OCTA can be used to measure the FAZ areas in both the SCP and DCP, beyond measurement of the FAZ area at the two-dimensional cross section used during FAG. The FAZ area in the SCP via OCTA showed a statistically significant correlation with the FAZ area determined by FAG, but there was no such correlation in the DCP. That said, the FAZ area in the DCP was positively correlated with a decrease in visual acuity among the patients, which may be an indicator of visual prognosis.