There are two types of RAOs:
- Branch retinal artery occlusion (BRAO) blocks the small arteries in your retina.
- Central retinal artery occlusion (CRAO) is when the central artery in your retina becomes blocked. This is a form of a stroke in the eye and is a risk factor for having a brain stroke. CRAO is a serious emergency, just like a brain stroke, so it is important to go to a hospital Emergency Room right away to be checked and treated immediately.
Color fundus photo (A) of a patient with multiple emboli resulting in branch retinal artery occlusions. Fluorescein angiogram (B) of the same patient showing retinal ischemia in the distribution of the BRAO.
What are Symptoms of a BRAO or CRAO?
The most common symptom of retinal artery occlusion is sudden, painless vision loss. You may lose vision in all of one eye (due to CRAO), or in part of one eye (from BRAO). Other symptoms include the sudden appearance of distorted vision or blind spots in your vision.
If you have any of these symptoms, go to a hospital Emergency Room right away. People who have RAOs are at high risk for having a brain stroke, especially right after and up to four weeks after having an RAO.
What are the Risk Factors for BRAO or CRAO?
- Smoking
- Obesity
- Older age
- Heart/lung disease
- Diabetes
- Elevated cholesterol
- High blood pressure
- Narrowing of the carotid artery
- Blood clotting disorders
How Is BRAO or CRAO Diagnosed?
Your retina specialist will perform diagnostic tests including:
- Fluorescein angiography which uses fluorescein dye traveling throughout the retinal arteries to show delay in filling or retinal ischemia.
- Optical Coherence Tomography (OCT) which provides detailed images of the central retina and shows swelling in the inner layers of the retina in the affected area, which over time atrophy.
- Your retina specialist will also communicate with your other physicians to order other tests involving your heart and carotid arteries which are necessary to help look for artery blockage elsewhere.
How is BRAO or CRAO treated?
While there is no clinically proven treatment for CRAO, several therapies may be tried to dislodge the clot including hyperventilation (breathing in a carbon dioxide-oxygen mixture to cause retinal arterial dilation), paracentesis (removal of fluid from the front of the eye using a small-gauge needle) or medication to lower the intraocular pressure, and ocular massage.
In order to be potentially effective, any such treatment must be deployed within a short time after symptoms start. Unfortunately, none of these therapies have been shown to predictably alter the natural history of disease. Thrombolytic therapy has also been tried but the evidence is mixed, and there is no consensus on its efficacy. The risks of systemic complications, such as bleeding, must also be considered. Current guidelines typically recommend considering thrombolytic agents only within 4 hours of symptom onset and in specialized centers where the risks can be managed.
It is imperative that anyone with an acute onset of CRAO or BRAO should be referred promptly to the emergency room or their primary care doctor to be evaluated for stroke risk.
Managing risk factors for stroke and heart disease is an important aspect of managing RAOs. It is important to try to identify the source of a clot that could have led to the RAO. Such tests include ultrasound of the carotid arteries and cardiac echocardiography. At times, blood test for specific abnormalities may be necessary as well.
Vision loss with CRAO is usually severe and irreversible. Even if your vision remains poor after RAO, it is important to continue being monitored by your retina specialist given complications can develop from RAO over time which require treatment in order to prevent further vision loss.
Complications after RAO include formation of new blood vessels in the retina or in the front of the eye that often bleed which can further decrease vision by causing vitreous hemorrhage and neovascular glaucoma. Laser photocoagulation is used to treat the ischemic areas in the retina in such cases to decrease the oxygen demand. In addition, intravitreal injections of anti-VEGF medications may also be used.
Source: American Academy of Ophthalmology