A retinal artery occlusion (RAO) is an obstruction of one or more arteries carrying oxygen to the nerve cells in the retina. The disease resembles a stroke. Oxygen is cut off during the blockage which can lead to permanent loss of vision. The blockage may be temporary and last only a few seconds or minutes. It may also be permanent. Most cases involve one eye.
The affected individual needs to seek medical attention urgently. One should also be transferred to a stroke center immediately.
Also Known As
- Eye stroke
- Blurry vision - Retinal artery occlusion
- Vision loss - Retinal artery occlusion
- Branch retinal occlusion (BRAO) - Is a blockage of the small arteries in the retina. It can affect a section of the eye. If it's only a tiny part involved, BRAO may not be easily noticed and may present no symptoms.
- Central retinal artery occlusion (CRAO) - Blocks the ophthalmic artery in the retina. It involves the whole area of the eye and causes the most damage.
Causes and Risk Factors
A clot or occlusion causes a RAO. Fat deposits or a build-up of cholesterol in an artery can may also lead to a RAO. The following are the risk factors associated with the disease:
- Pregnant women
- Diabetic patients
- Obese individuals
- Carotid artery disease
- Individuals in their 60’s
- Individuals who smoke
- Use of oral contraceptives
- Blood platelet abnormalities
- High levels of cholesterol
- Intravenous abuse of drugs
- Those with giant cell arteritis
- Men are more likely to be affected than women
- Those with hypertension or high blood pressure
- Hyperlipidemia - Abnormally high levels of lipids in the blood
- Coagulopathy - A bleeding disorder where the blood may fail to clot
- Those who have cardiovascular disease- Faulty heart valves, tumors in the heart, and abnormal heart rhythms
Signs & Symptoms
These symptoms may be present in a RAO:
- Distorted vision
- Loss of side vision
- Painless loss of vision
- Failure to perceive light
- Sudden, complete vision loss
- Blind spots in the field of vision
- The neck artery becomes narrow
The eye care professional will perform a thorough eye examination to check for signs of damage on the retina. To do this, he/she will dilate the eyes using dilating eye drops. The following tests may also be conducted:
- Check the reflexes of the pupil
- Check for intraocular pressure (IOP)
- A slit-lamp examination to examine the structures in the front of the eye
- A visual field examination where he/she examines the individual’s side vision
- Visual acuity test to check how well an individual can read from a chart a distance away
- An ultrasound of the carotid arteries - These are main blood vessels that transport blood to the brain and eyes
- More imaging photographs using optical coherence tomography (OCT) to reveal swellings in the inner layer of the retina
- Patients over 50 with giant cell arteritis can have blood tests to check for the cause of inadequate blood supply to the retina
- An ultrasound of the heart (echocardiogram) - This is imaging that uses sound waves to create pictures of the heart. Just like in the ultrasound of the carotid arteries, the goal is to find the source of the blocked retinal artery
- Fluorescein angiography - The use of a special yellow dye that the professional injects into a vein in the arm. A special camera will take images of the retina as the dye travels through the retinal arteries. The pictures show how many arteries are blocked
Treatment of RAO aims to address the blockage of the arteries and maximize on visual outcomes.
Treatment must commence within a few hours after the symptoms begin to show. Doctors are yet to agree on a particular line of treatment for RAO. There is no consistency in the procedures that have been used so far.
Treatment may include a clot-busting drug and removal of liquid from the eye. Removing the liquid moves the clot away from the retina.
A patient can also inhale carbogen, a mixture of carbon dioxide and oxygen. Once breathed in, the mixture will cause the dilation of the retinal arteries. A combination of 95% oxygen and 5% carbon monoxide is sufficient.
A patient suspected of giant cell arteritis will be treated with steroids for 6-12 months.
The eye doctor might perform a biopsy after two weeks of the patient taking the corticosteroids.
Certain medications are administered to help lower intraocular pressure.
An ocular massage using a three-mirror contact lens or the thumb can help to reduce the inadequate supply of oxygen to the retina.
For a patient who develops neovascularization (growth of new blood vessels), surgery is necessary if the disease progresses to uncontrolled glaucoma or vitreous hemorrhage. Such a patient needs very close follow-up.
Some patients recover from RAO to regain vision. However, the vision may not be as good as it was before. Failure to treat the disease promptly (within 2 hours) can lead to permanent loss of vision.
New blood vessels can form in the iris, retina or iridocorneal angle leading to further loss of vision. It can also cause pain in the affected eye.
About 15%-30% of patients with CRAO have a cilioretinal artery in the eye. This artery reduces the likelihood of damage to the central vision.
The same measures used to prevent vascular diseases such as coronary heart disease can be applied. They include physical activity, a low-fat diet, losing weight for overweight persons and not smoking.