When one of the vessels carrying blood to the retina gets congested, it can result in vision loss. This may happen abruptly and without any pain – a condition called central retinal artery occlusion (CRAO).
Your retina is the layer of nerve tissue at the back of your inner eye. It works like a little video camera that senses light and turns pictures into electrical signals. Your optic nerve transmits these signals to your brain. The problem starts when an obstruction of a blood vessel happens in the retina. This is a very serious condition that needs immediate intervention. That’s because if a blood clot breaks free and travels to the brain, it could result in a stroke.
Symptoms and Warning Signs
If you have CRAO, the jam in your artery happens just as it enters your eye before it splits into two to four divisions. It affects the entire nerve layer of the retina in such a short amount of time. You will typically notice a loss of vision in one eye, which occurs quickly and painlessly over a matter of seconds. In 19 out of 20 cases, the loss of vision is so significant that you can just see fingers to count them, but nothing more. CRAO affecting both eyes is extremely rare, only about 2 in 100 cases.
Different Types of CRAO
- Non-Arteritic Permanent
Platelet-fibrin thrombi and emboli due to atherosclerotic disease account for the majority of CRAO cases, nearly two-thirds of it. Diabetes mellitus, coronary artery disease, arterial hypertension, cerebral vascular accidents, and smoking tobacco are among the factors that can significantly increase the risk of CRAO.
- Non-Arteritic Transient
Also known as transient monocular blindness, non-arteritic transient CRAO accounts for 15 to 17 percent of cases and it has the best visual prognosis. In animal models, the transient vasospasm caused by serotonin discharge from platelets on atherosclerotic plaques has been observed as a mechanism of this type.
- Non-Arteritic With Cilioretinal Sparing
A cilioretinal artery has been found to be present in as much as 49.5% of patients. Whether this leads to preserved perfusion to the retina rests upon how much of the area it supplies.
This is always due to giant cell arteritis, which occurs in nearly 4.5 percent of all CRAO cases.
Treatment and Management
There is still no universal consensus on the best treatment for CRAO, although early administration of intravenous thrombolytics reveals promising results. The following therapies are reported to improve the condition:
- Supplemental oxygen
- Direct digital ocular massage to prompt oscillations of intraocular pressure and remove the offending thrombus
- Hyperventilation into a paper bag or inhaled 10% carbon dioxide to induce vasodilation and respiratory acidosis
- Intraocular pressure reduction with mannitol, acetazolamide, topical timolol, or anterior chamber paracentesis (often prescribed in conjunction with digital ocular massage)
Central retinal artery occlusion requires prompt medical attention. You may be at a higher risk if you are older or have diabetes, glaucoma, or high blood pressure. Talk to your healthcare provider about possible screening tests. If you receive a diagnosis, be sure to research on any new medicines and treatments and ask if your condition can be treated in other ways.
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Hayreh SS, Zimmerman MB
Am J Ophthalmol. 2005 Sep; 140(3):376-91.
Cilioretinal arteries. A study based on a review of stereo fundus photographs and fluorescein angiographic findings.
Justice J Jr, Lehmann RP
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