Recently I had a patient visit my office with a very frightening visual experience. While working around the house late one afternoon, he noticed that his vision went totally black in one eye. He denied having any head or eye trauma, dizziness, headache, or difficulty speaking. After examining this patient’s eye, he was diagnosed with a central retinal artery occlusion.
The central retinal artery is the largest main artery that feeds blood to the inside layer of the eye, known as the retina. Once this artery enters the cavity of the eyeball it branches off into many smaller arteries. Blood clots that develop anywhere in the arterial system can break off and become emboli, with the potential to become lodged elsewhere in the body. This particular patient of mine had a large clot restricting blood flow thru the central retinal artery but also had several smaller clots lodged in multiple smaller retinal arteries.
What happens to the vision if a clot becomes stuck in a retinal artery? A large embolus that becomes lodged in the central retinal artery is called a central retinal artery occlusion (CRAO) and results in complete vision loss. Smaller emboli can block branches or tributaries of the central retinal artery, called branch retinal artery occlusions (BRAO). BRAOs can yield a range of vision loss from upper or lower field of view loss to peripheral vision loss depending on the size of artery that is blocked. The vision loss in both CRAO and BRAO is sudden and painless.
Is the vision loss permanent? It can be depending on how long the clot remains lodged in the artery or whether the clot is restricting 100 percent of the blood flow thru it.
What are the causes of the emboli? Cholesterol emboli are the most common. The source of these emboli is usually from the carotid artery. Hypertension, diabetes, high cholesterol, and smoking are all risk factors for cholesterol emboli. Platelet and calcific emboli are usually due to heart disease, and more specifically heart valve disease. Talc emboli can also be seen and these are due to intravenous drug use.
There are also several diseases that can precipitate a CRAO or BRAO. These diseases include giant cell arteritis, lupus, Lyme disease, sickle cell disease. Oral contraceptive use has also been linked to retinal artery occlusions.
Appropriate diagnosis and management of patients with retinal artery occlusions can have a significant impact on a patient’s life expectancy and ocular health. These patients have a reduced survival rate, with the major cause of death being cardiovascular disease. Blood thinners are usually prescribed immediately on diagnosis to help decrease the risk of further vascular compromise.