Retinal vein occlusion

Summary

• Retinal vein occlusion (RVO) is the obstruction of the vein draining blood from the eye.
• Risk factors include cardiovascular disease, diabetes, hypertension and glaucoma.
• Some RVO will resolve by itself, while more serious forms can lead to permanent sight loss.
• Laser treatment may help in some cases.

Alternative names

• Retinal apoplexy
• Venous stasis retinopathy
• Retinal vein thrombosis

Definition

The retinal vein drains blood from the retina. If this blood flow is occluded (blocked), it can lead to severe damage to the retina, sight loss or even complete blindness in one or both eyes. Retinal vein occlusion is most common in people over 60.

Blockage of the vein leads to backed-up pressure in the retinal capillaries and this can cause haemorrhaging, fluid leakage and oedema (swelling) of the retina. Macular oedema occurs when fluid collects in the macula (the spot at the centre of the retina ).

The severity of these symptoms depends on how complete the blockage is. Sometimes the obstruction cuts off blood supply completely, causing tissue death. This is called ischaemia or non-perfusion.

• Non-ischaemic RVO is often not very severe; it may clear up by itself without permanent visual loss.
• Less common is chaemic RVO and has a much worse prognosis.
• The extent of damage also depends on the location of the occlusion.
• If the occlusion is in the smaller branch veins, only a portion of the retina may be affected. 
• More rarely, the central retinal vein, which collects the blood from all the capillaries, can become occluded, which involves the entire retina.
• The macula, which is responsible for high-acuity vision, may or may not be affected.

Causes 

RVO may have several causes. Risk factors, as for other circulatory problems, include ageing, high blood pressure, diabetes, high cholesterol, smoking, and cardiovascular disease.

Other risk factors may include:

• Damage to the wall of the blood vessel, through inflammation or trauma
• Abscesses or tumours in the eye
• Blood coagulation or hyperviscosity disorders
• Dehydration
• Use of drugs that can cause vasoconstriction, e.g. cocaine
• A variety of other underlying medical conditions

Symptoms

Symptoms appear suddenly in one eye, and may include:

• Blurred or lost area of visual field
• Loss of central vision
• Sharp reduction in visual acuity (clarity)

These symptoms may get progressively worse as swelling in the eye increases. Symptoms of ischaemic RVO may be particularly acute.

Sometimes, there are no symptoms and RVO is detected during a routine eye examination.

Diagnosis

An ophthalmologist will do eye tests for visual acuity, visual fields, pupil reaction, and intraocular pressure. Examination with an ophthalmoscope will show dilated blood vessels and haemorrhaging. A technique called fluorescein angiography may be used to determine where the blockage is and detect macular oedema. Optical coherence topography (OCT) may be used to further assess the retina and the retinal vasculature.

The ophthalmologist will also refer you to your GP or physician for a full cardiovascular workup to see if any underlying causes or risk factors can be found.

Treatment

Treatment is difficult and focuses on reducing macular oedema, preventing increased intraocular pressure, and preventing further sight loss and complications.

If ischaemia has occurred, it is unlikely that treatment will improve vision significantly.

A technique called argon laser photocoagulation can seal leaking capillaries, and  further damage may be prevented.

Some other treatments may be effective:

• Corticosteroids can reduce inflammation and may reduce macular oedema.
• Acetazolamide may also reduce oedema.
• Eyedrops that lower eye pressure may be needed.
• In an experimental treatment, laser has been used to create an alternative exit route for blood from the eye.
• Various surgical techniques may be used in certain cases.

Prognosis

Ischaemic RVO may have serious complications and the visual outcome is poor.

Non-ischaemic RVO usually has a good prognosis, although sometimes it converts to ischaemic RVO.

Note that people who have had RVO are at higher risk for strokes, heart attacks, and other cardiovascular problems.

Complications

• RVO may lead to decreased visual acuity or even complete blindness.
• The underlying cause of the RVO may be a serious, potentially life-threatening disease.
• Scar tissue may form, causing distorted vision.
• Neovascularisation (the growth of new, abnormal blood vessels) can arise where blood flow has been blocked to large areas of capillaries. This may lead to bleeding into the vitreous humour of the eyeball. Abnormal blood vessels may even pull at and detach the retina.
• Neovascularisation may also happen in the iris, which can cause very high pressure in the eyeball, with pain, severe vision loss, and sometimes even loss of the eye. Laser photocoagulation treatment may be effective in managing neovascularisation.

When to call your doctor

Call your doctor if you experience any RVO symptoms. If you have been diagnosed with RVO, it is very important to have follow-up consultations to monitor the disease and prevent complications.

Prevention

You can lower your risk for any cardiovascular problems by following a healthy diet, avoiding smoking, doing regular exercise, and having regular medical check-ups (including testing your blood pressure, blood cholesterol, and blood glucose).

Reviewed by Dr Clive Novis, Ophthalmologist, June 2011