Retinal Vein & Artery Occlusion
Our sense of vision relies primarily on the retina, which is a photosensitive membrane that acts as an intermediary between the eye and brain. When light enters the eye through the lens, the retina captures this information and translates it into neural signals for the brain to interpret into an image. To perform this incredible feat, the retina requires a constant supply of blood and oxygen, which is provided by the retinal vascular system. The main components of the retinal vascular system are the central retinal artery and the central retinal vein.
The Central Retinal Artery
The retina receives its supply of oxygenated blood from the central retinal artery, which extends from the ophthalmic branch of the internal carotid artery (the artery located in the neck). The central retinal artery runs along the optic nerve and delivers blood through a system of small branches that are distributed throughout the retinal tissue.
Central Retinal Artery Occlusion (CRAO)
Central retinal artery occlusion (CRAO) is when a blood clot forms in the central retinal artery and is sometimes referred to as an “eye stroke.” The primary symptom of CRAO is a sudden, painless loss of vision. CRAO most commonly occurs in patients who are between 50 and 70. It is also more common in male patients.
CRAO can lead to irreversible vision loss if not treated within 24 hours. The sooner you can get treatment, the more likely you will be able to retain some vision. Patients should also keep in mind that CRAO increases a patient’s risk of having a cerebral stroke, so it’s essential to seek medical attention immediately if you experience painless vision loss.
Branch Artery Occlusion (BRAO)
If a blood clot is located in one of the branches that stem from the central retinal artery, it is known as branch retinal artery occlusion (BRAO). When the affected artery provides the macula with oxygenated blood, BRAO can result in loss of central vision. Like CRAO, BRAO indicates the increased possibility of having a cerebral stroke and should be treated as a medical emergency.
The Central Retinal Vein
As the blood moves through the retinal system and fuels the nerve cells, its oxygen levels deplete. The central retinal vein drains the deoxygenated blood from the retinal branches so that the blood can return to the heart where its oxygen levels will be replenished. Like the central retinal artery, the central retinal vein has its own system of branches distributed throughout the retinal tissue.
Central Retinal Vein Occlusion (CRVO)
When a blockage occurs in the central retinal vein, it is known as a central retinal vein occlusion (CRVO). The blockage causes structural damage to the veins, which leads to bleeding and fluid leakage into the retina. If the bleeding and leakage occur near the macula, central vision will become blurry and/or distorted. Because the retinal vein is damaged, new veins begin to form. These new veins are abnormal, fragile, and prone to bleeding and leaking into the vitreous, which leads to tiny dark shapes known as floaters appearing in your field of vision.
CRVO is commonly associated with a wide range of underlying conditions, including high blood pressure, diabetes, glaucoma, and blood disorders.
Branch Retinal Vein Occlusion (BRVO)
Branch retinal vein occlusion (BRVO) is when the smaller blood vessels that branch off from the central retinal vein become blocked. If the affected veins are close to the macula, it can cause macular edema (swelling of the macula). BRVO leads to painless, diminished central vision that is blurry and/or distorted. In some cases, new abnormal blood vessels grow and bleed into the eye.
Treatment for Retinal Artery & Vein Occlusions
Retinal vascular diseases are cause for concern and should be addressed and monitored by a retina specialist as quickly as possible. Treatment can range from managing underlying conditions, such as diabetes and high blood pressure, to laser photocoagulation surgery.
In cases where abnormal blood vessel growth is present, anti-vascular endothelial growth factor (anti-VEGF) medications will likely be recommended. Anti-VEGF medications help stop the growth of abnormal blood vessels by inhibiting the protein responsible for vein growth. These medications are injected directly into the eye using a very thin needle. Anti-VEGFs are very effective in managing retinal vascular diseases and can help patients maintain their vision.