The branch veins may be classified as macular or major. In these cases, only one-half of the field is affected.
Retinal ischemia carries a poor visual prognosis.
The nonischemic variety has a variable course, but is potentially benign and self-limited with a good visual outcome. Three mechanisms are postulated to cause retinal vein occlusion. Primary venous disease, such as degenerative or inflammatory processes Most researchers believe the pathogenesis is multifactorial. The anatomic location of occlusion varies depending on the type of venous occlusion. However, mortality and morbidity may occur secondary to an underlying pathology.