[Patterns of arteriovenous crossings in branch retinal vein occlusion].

The fundus color and fluorescein angiographic photographs of 82 eyes in 76 cases with recent branch retinal vein occlusion (BRVO) were compared with those of 82 eyes in 82 cases without BRVO in the age-sex-matched control group to determine the relationship between the arteriovenous crossing and BRVO. It was found that 90.3% of the crossings at the obstructive sites were located at the temporal quadrant, especially the superior temporal quadrant, and the artery lay anterior to the vein at the crossing in all of the eyes with BRVO (100%). In the 3 subgroups of the control group, the rates of the crossing at the obstructive site with the artery lying anterior to the vein were 67.1%, 70.0% and 74.4% in the B, C and D subgroups, respectively. Each of the rate of the 3 subgroups was compared with that of the BRVO group, statistically. There were significant differences (P < 0.001). The results suggest that a crossing with artery lying anterior to the vein possibly be one of the risk factors of BRVO and the artery exerting mechanical pressure upon the vein be the main cause in the pathogenesis of BRVO.