What is Central Retinal Artery Occlusion?
Central retinal artery occlusion (CRAO) occurs due to a lack of blood supply to the retina caused by an occlusion or blockage in the central retinal artery which normally supplies blood and oxygen. It is a medical emergency characterized by acute, profound, and painless loss of vision. It usually occurs in those aged 60-65 years and is more common in men.
Blockage in the central retinal artery causes edema in the inner layer of your eye and tissue death (necrosis). The retina loses its transparency and becomes a yellowish-white color as a result.
CRAO may fortunately last only a few seconds or minutes if the blockage breaks up and restores normal blood flow to the retina; however, in extreme cases it can be permanent.
What is the Retina?
The retina is the inner layer of the eye that consists of light-sensitive cells called rods and cones which help us to see in dim and bright light respectively. The retina collects visual signals and sends them through the optic nerve to the brain, where they are processed and interpreted as images.
What are the Symptoms of Central Retinal Artery Occlusion?
The common symptoms of central retinal artery occlusion may include:
- Opacity (cloudiness) of the eye
- A scar in the inner layer of the retina
After a few weeks, the opacification resolves. However, the retina remains thin and damaged.
What are the Risk Factors for Central Retinal Artery Occlusion?
The chances for central retinal artery occlusion are higher in people with the following diseases:
- Hypertension: high blood pressure
- Diabetes mellitus: high blood sugar
- Hypercholesterolemia: high blood cholesterol levels
- Embolism: a blockage in the blood vessel due to a blood clot or air bubble
- Heart disorders which may include atherosclerosis and valve defects
How is Central Retinal Artery Occlusion Diagnosed?
Your eye specialist/ophthalmologist will perform a detailed eye exam and assess your retina. The diagnostic tests will include:
- Response of pupil to light to determine any defect
- Optic nerve examination to detect any temporal arteritis: inflammation of the blood vessels near the temples
- Cherry-red spot in the retina
- Imaging tests such as carotid ultrasonography, optical coherence tomography (OCT), fluorescein angiography, and ocular magnetic resonance imaging (MRI) to provide detailed images of the retina
Your past medical history will be explored and any current symptoms reviewed. Based on the results of your eye diagnosis, a suitable treatment will be planned.
What are the Treatment Options for Central Retinal Artery Occlusion?
Central retinal artery occlusion is managed with the same approach as that of a stroke. The aim of CRAO treatment is to identify the blockage site in the blood vessel and improve the blood supply in the central retinal artery. The different approaches to treat central retinal artery occlusion include:
- Ocular massage with the thumb to dislodge the clot
- Intraocular pressure reduction with local or systemic medications
- Anticoagulation therapy
- Systemic steroid therapy
- Hyperbaric oxygen therapy (HBOT): breathing almost pure oxygen in a specialized chamber
- Carbogen (a mixture of 95% oxygen and 5% carbon dioxide)-inhalation therapy
- Paracentesis: fluid removal from the front of the eye using a small-gauge needle
The choice of treatment depends on the patient’s overall health and age.