Retinal vein occlusion
Retinal vein occlusion (RVO) is a blockage in one of the veins that drain blood from the retina. This blockage prevents normal blood flow, leading to leakage, swelling, and sometimes bleeding inside the eye. The condition can affect vision to varying degrees, depending on the type and severity of the blockage. While it is not painful, it should be investigated promptly, as early management can help preserve sight and reduce the risk of further complications.
Types of retinal vein occlusion
The retina has a network of veins that carry blood away from its tissue. When a blockage occurs, it can affect either a smaller branch vein or the main central vein. The type of vein involved influences both the severity of symptoms and the treatment approach.
- Branch retinal vein occlusion (BRVO): The blockage occurs in one of the smaller branch veins. It usually affects only part of the vision and often spares central sight unless the macula is involved. BRVO is more common than CRVO and generally has a better outlook, especially with early treatment.
- Central retinal vein occlusion (CRVO): A blockage in the main vein that drains blood from the retina. This usually affects the whole retina and can cause more severe vision loss. CRVO can be milder (non-ischaemic) or more severe (ischaemic), and often needs closer monitoring and more intensive treatment.
What causes retinal vein occlusion?
RVO usually develops when a retinal vein becomes narrowed or compressed by a nearby artery, often as a result of hardening of the arteries. This increases the chance of a blood clot forming in the vein. Several factors can raise the risk:
- High blood pressure
- Diabetes
- High cholesterol
- Glaucoma (raised pressure inside the eye)
- Smoking
- Certain blood clotting disorders
- Age over 50
Symptoms
RVO symptoms can appear suddenly or develop over hours to days. They may include:
- Blurred or distorted vision in one eye
- A sudden patch of missing vision
- Dark spots, floaters, or haze in vision
- Reduced ability to see fine details
Sometimes the vision loss is mild, but in more severe cases it can be significant.
How serious is retinal vein occlusion?
The impact depends on the location and extent of the blockage, and whether complications develop. Potential complications include:
- Macular edema: Swelling in the central retina that blurs central vision.
- Neovascularisation: Growth of new, fragile blood vessels that can bleed or raise eye pressure.
- Secondary glaucoma: Elevated pressure in the eye caused by these new vessels.
Early diagnosis and ongoing monitoring help reduce the risk of permanent sight loss.
Diagnosis
RVO is diagnosed during a dilated eye examination. Additional tests may include:
- Optical coherence tomography (OCT): To detect swelling in the retina.
- Fluorescein angiography: A special dye test to show areas of blockage or leakage.
- Blood tests: To check for underlying conditions such as high cholesterol, diabetes, or clotting abnormalities.
Management and treatment options
There is no way to unblock the vein directly, but treatment focuses on managing complications and protecting vision. Depending on the findings, your specialist may recommend:
- Intravitreal injections (anti-VEGF drugs or steroids) to reduce swelling in the retina.
- Laser treatment to control abnormal vessel growth or leakage.
- Control of underlying health conditions such as blood pressure, cholesterol, and diabetes.
Prognosis
Some people experience gradual improvement in vision as the eye recovers, while others have ongoing swelling or vision loss. The outlook is generally better in BRVO than in CRVO.
Lifelong monitoring is important, as RVO can recur in the same or the other eye.
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