The effect of macular edema on quantitative analysis of foveal avascular zone in branch retinal vein occlusion eyes

Abstract

Objective To observe the effect of different macular edema on the area of foveal avascular zone (FAZ) and its correlation in eyes with branch retinal vein occlusion (BRVO). Methods A total of 72 patients (75 eyes) diagnosed with BRVO were included in the study. There were 40 patients males (42 eyes) and 32 females (33 eyes), with the mean age of (56.00±9.96) years. All the eyes were examined by BCVA, intraocular pressure, slit lamp microscope combined with preset lens, fundus color photography and optical coherence tomography angiography (OCTA). BRVO patients were divided into two groups according to the degree of macular edema: group M300 that was CRT ≥300 μm (38 patients, 39 eyes) and group L300 that was CRT<300 μm (34 patients, 36 eyes). The macular angiography scan protocol covered a 3 mm×3 mm area. The parameters of macular were measured by the built-in measurement software of the system: (1) area of FAZ, perimeter of FAZ (PERIM), avascular index of FAZ (AI), vascular density within a width of 300 μm around the FAZ region (FD-300); (2) central retinal thickness (CRT); (3) vascular density (VD): the superficial central fovea vascular density (SFVD), the deep central fovea vascular density (DFVD), the superficial hemi-macular vascular density (SHVD), the deep hemi-macular vascular density (DHVD). Spearman test was used to test the correlation between FAZ area and other parameters in each group. Results The FAZ area in group M300 and L300 were 0.388±0.166 mm2 and 0.596±0.512 mm2, respectively. The results of Spearman test showed that the FAZ area of group M300 was positively correlated with PERIM and AI (r=0.932, 0.591; P=0.000, 0.000), negatively correlated with SFVD, DFVD and SHVD (r=−0.490, −0.429, −0.339; P=0.002, 0.006, 0.035). But there was no significant negative correlation between FAZ area and FD-300, CRT, DHVD in group M300 (r=−0.129, −0.053, −0.400; P=0.435, 0.749, 0.395). The FAZ area in group L300 was positively correlated with PERIM and AI (r=0.887, 0.633; P=0.000, 0.000), negatively correlated with SFVD, DFVD, SHVD and DHVD (r=−0.413, −0.643, −0.630, −0.370, −0.411; P=0.012, 0.000, 0.000, 0.026, 0.013). But there was no significant positive correlation between FAZ area and FD-300 in group L300 (r=0.093, P=0.590). Conclusion FAZ area varies with the degree of macular edema. The degree of macular edema is higher, the FAZ area is smaller. FAZ area is positively correlated with PERIM and AI significantly, and negatively correlated with SFVD, DFVD and SHVD. Key words: Retinal vein occlusion; Macular edema; Foveal avascular zone; Tomography, optical coherence