Retinal Vascular Occlusions
There are four types of retinal vascular occlusions, also known as RVO, including:
- Branch Retinal Vein Occlusion (BRVO)
- Central Retinal Vein Occlusion (CRVO)
- Branch Retinal Artery Occlusion (BRAO)
- Central Retinal Artery Occlusion (CRAO)
All types of retinal vascular occlusions cause sudden and painless loss of vision. Usually only one eye is affected over the lifetime of a patient. Vision can vary depending upon the exact RVO, but can range from asymptomatic to profound legal blindness. Treatments exist, but results differ.
There are occlusions affecting veins and disorders affecting arteries of the retina.
Central and branch retinal vein occlusions differ only by the amount of retina which is diseases. CRVO involve the entire retina. BRVO affects 50% or less of the retina.
Occlusions of the venous system are usually thought to be due to local hardening of the blood vessels and NOT usually associated systemic cardiovascular disease (i.e. heart attack, stroke). Diabetes and high blood pressure can increase the chance of a vein occlusion occurring, but they do NOT directly cause the veins to plug.
The difference between the central and branch artery occlusion is the same as their venous cousins. Central affects the entire retina. Branch artery occlusions affect less than 50% of the retina.
Artery occlusions occur when a piece of blood clot, cholesterol, fat or platelets physically block or plug the artery. These are different types of “emboli” which can occlude the artery. Most “emboli” are cholesterol plaque from the carotid artery. A tiny piece of cholesterol breaks off into the blood stream, travels to the retina and plugs a blood vessel.
Vision loss from a CRAO is usually profound and permanent. Smaller branch artery occlusions are associated with blind spots, some elements of the vision may be normal – all depending upon the amount of retina involved.
Both heart attacks and strokes occur by similar mechanisms. The presence of a CRAO or BRAO may lead to further assessment of the patient’s chances of developing stroke or heart attack.
Though vision loss from artery occlusions tends to be permanent, follow up is necessary to look for signs of neovascularization which can lead to a very painful type of glaucoma.