Acute Branched Retinal Vein Occlusion
Major BRVO: Occlusion of retinal vein that drains one of the quadrants
Macular BRVO : Occlusion of a venule within the macula
BRVO can also be ischemic/ non-ischemic- ischemic BRVO: Ischemic is >5-DD of non-perfusion on FFA
Risk factors: Hypertension, diabetes, hyperlipidemia, glaucoma etc
Young patients - High homocysteine, hypercoagulable states, use of oral contraceptive pills etc.
What is the most common site and why is it so?
The superotemporal quadrant is the most common to be involved as it has more number of arteriovenous crossings.
Retinal artery and vein share a common adventitial sheath - artery compresses the vein.
Venous obstruction→ Increased venous pressure→ Overloading of collateral draining capacity→ Macular edema and ischemia → Unrelieved venous pressure→ Rupture of vein wall and intraretinal hemorrhage
Dilatation and tortuosity of venous segment distal to the site of occlusion, proximal attenuation
Retinal hemorrhages confined to the distribution of a retinal vein are characteristic- wedge shaped pattern with apex towards site of obstruction
Flame-shaped hemorrhages and dot -blot hemorrhages predominate
Complete obstructions result in extensive intraretinal hemorrhages, cotton-wool spot formation, and widespread capillary nonperfusion
Neovascularisation can occur
Causes of visual loss in BRVO: