CRAO, or central retinal artery occlusions, occur when the entire blood supply to the retina is lost due to a blockage of the central retinal artery in the eye. CRAO causes sudden and painless loss of vision as with other types of retinal vascular occlusions (RVO).
Unlike occlusions of retinal veins (central retinal vein occlusions and branch retinal vein occlusion), CRAO may be a sign of serious systemic disease. Diagnosis of an artery occlusion should be coordinated with a systemic evaluation of cardiovascular disease.
There are 4 types of retinal vascular occlusions (RVO):
“Central” retinal artery occlusion almost always involves the entire retina. Profound vision loss occurs due to involvement of the entire retina usually to include the macula. A small percentage of patients have an additional “cilio-retinal” artery which may allow the macula (provides central vision) to be spared. This accessory artery is normally present in about 10-15% of all patients.
The hallmark of CRAO, as with other retinal vascular occlusions, is sudden painless loss of vision.
A small particle of cholesterol, fat or calcium can break off from the carotid arteries or a diseased heart and plug the retinal artery. This particle is called an embolus. Rarely, clumps of platelets can also form an embolus.
An embolus can travel into the eye and cause the entire artery to get plugged. The same mechanism can occur with stroke and heart attack. In the eye, the entire retina loses oxygen by the lack of blood supply and vision is lost.
Vision is generally permanent in cases of CRAO.
Immediate treatment is focused on dislodging the embolus and, in theory, restoring blood circulation. Ideally, blood flow should be restored with 24 hours after the occlusion starts.
Most patients are not seen until well after the initial 24 hours.
Though little can be done to improve the vision loss, follow up is important to prevent complications from loss of blood supply. As with all forms of vascular occlusions, complications from neovascular glaucoma can develop and lead to a very painful condition.
Though vision loss is usually permanent, patients must be aware that complications can occur from any type of retinal vascular occlusion. All patients with RVO (retinal vascular occlusions) are at risk for developing neovascular glaucoma, a very painful type of glaucoma.
Patients with either type of artery occlusion are at increased risk for heart attack or stroke. Patients with either BRAO or CRAO should have an evaluation for risk of developing heart attack or stroke by their PCP or cardiologist.