The retina of the eye is served by a primary artery and vein. Branch retinal vein occlusion (BRVO) occurs when the branches of the retinal vein become obstructed.
When a vein becomes blocked, blood and fluid leak into the retina. This can cause the macula to swell, impacting central vision. Over time, if circulation is compromised, nerve cells in the eye may deteriorate, leading to further vision loss.