What is retinal vessel occlusion?
A retinal vessel occlusion is a blockage in the blood vessel at the back of your eye that can result in sight loss. There are two types of retinal blood vessels, arteries (retinal artery occlusion) and veins (retinal vein occlusion). Either of these can become blocked and each of them can affect the eye in different ways.
Artery occlusions are commonly caused by atherosclerosis or an embolus. Atherosclerosis is where plaque builds up on the inside walls of arteries. These plaques are known as atheroma.
Sometimes, part of an atheroma plaque which forms in a larger artery may break off. This piece is known as an embolus. An embolus can then flow with the blood, potentially blocking a smaller vessel downstream – this is called an embolism.
A retinal artery occlusion causes a sudden loss of sight (usually over seconds). You should attend your local hospital Accident and Emergency (A&E) department straight away if you suddenly lose all or part of your vision in one or both eyes.
The cells on the retina are very sensitive to a lack of blood supply, which can result in permanent sight loss. The chances of restoring any vision are low, but if you are seen at the hospital within a few hours of having a retinal artery occlusion, then your ophthalmologist may try some treatment.
Retinal vein occlusion is commonly caused by a blood clot (thrombosis) forming in the vein. This causes the vein to become blocked. It’s not always known exactly why the blood clot has formed.
Atherosclerosis can also play a role in retinal vein occlusions. Narrowing of the retinal arteries due to atherosclerosis can cause the hardened arteries to press onto the nearby veins which have thinner walls. This can cause the veins to narrow and disturb the blood flow in them. This narrowing can potentially cause an occlusion.
A retinal vein occlusion causes a dimming or blurring of all or part of your sight in one eye. This usually happens over a period of hours or days. If you experience any change in your vision, you should have your eyes examined as soon as possible.
A branch retinal vein occlusion (BRVO) may only cause a small amount or area of vision loss. It can often get better without any treatment. A central retinal vein occlusion (CRVO) affects more of your vision, usually all of the vision in the eye.
Further information can be found on RNIB's retinal vessel occlusion webpage.
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