Anterior location of the crossing artery in branch retinal vein obstruction.

We evaluated retrospectively the cases of 25 patients (26 eyes) with a recent, temporal, branch retinal vein obstruction to determine the relative anatomic position of the obstructed vein in relation to its crossing artery. In 26 (100%) of 26 eyes, the artery lay anterior to the vein, toward the vitreous cavity. A control group was obtained by evaluating the relative anatomic position between the branch retinal artery and vein at an equivalent crossing site along the opposite vascular arcade within the same eye. In the control crossing sites, the artery lay anterior to the vein 65% (15/23) of the time. We conclude that the likelihood that the artery will lie anterior to the obstructed vein at the site of blockage in a branch retinal vein obstruction is substantially greater than what would be expected by chance alone. This anatomic relationship between artery and vein probably plays a role in the cause of a branch retinal vein obstruction and may have therapeutic significance in light of a recent report concerning surgical treatment of such obstructions.