Retinal Vein Occlusion

A retinal vein occlusion is a sudden painless loss or reduction in vision and usually occurs in older people. A retinal vein occlusion is when a vein that carries blood out of the retina (light sensitive layer at the back of the eye that allows you to see) becomes blocked.

The blocked retinal vein then leaks blood and other fluids into the retina. This leakage of blood & fluids causes swelling, reduced oxygen supply and damage to the retina. There are two types of vein occlusions:

• Branch retinal vein occlusion BRVO: a blockage in one of the four veins that drains blood from one quadrant of the retina. The bleed seen on the retina from a branch retinal vein occlusion occurs in one of the quadrants of the retina.

• Central retinal vein occlusion CRVO: a blockage occurring at the main retinal vein (central vein is formed by the four branch veins), the central vein drains blood away from the whole retina. A blockage and subsequent leakage of the central vein causes more severe visual or vision loss.

Branch retinal vein occlusion

• Blurry vision

• Floaters

• Vision loss in a part or all of the eye

• Sudden or progresses over a couple of hours or days

• Painless

Central retinal vein occlusion

• Sudden complete loss of vision or blurry vision

• Usually painless

• Floaters

• Distorted or wavy vision

• Sudden or progresses over a couple of hours or days

• Some may have pain and feel pressure in the affected eye

Retinal vein occlusions occur due to a blockage in the flow of blood. The exact cause is unknown but there are factors that can place you at greater risk of having a retinal vein occlusion.

• It usually occurs in over 50 year olds

• People with high blood pressure

• People with high cholesterol

• Patients with glaucoma

• Diabetes

• People that smoke

• If you have a rare blood disorders

• If you have arteriosclerosis - hardening of the arteries

Lower your risk by eating a healthy diet, stop smoking, exercising on a regular basis and keep your body weight down. Also keep on top of any health problems or concerns you may have.

If you have the following risk factors, address these as soon as you can to prevent another vein occlusion from occurring

• High cholesterol, speak to your GP about changing your diet and cholesterol lowering tablets called statins

• High blood pressure, have this monitored by your GP and if it is high you may need blood pressure tablets

• Glaucoma (high eye pressure) patients should be receiving treatment, untreated Glaucoma patients are at greater risk of a retinal vein occlusion

• If you are diabetic, ensure you have good control of your diabetes, speak to your GP about this

• Smoker; try and stop! You are at more risk of a retinal vein occlusion if you smoke

• Rare blood disorders are usually detected by a blood test, and should be under supervision of a blood disorder specialist

If you have a branch retinal vein occlusion or central retinal vein occlusion, the main aim is to preserve your vision and keep it stable. You cannot unblock a blocked vein.

Damage caused by a vein occlusion to the retina is either by:

-Obstruction or blockage to the blood flow in the vein – no treatment available

-Fluid accumulating from the leakage, at the macula, causing macula oedema – treatment is available

Macula Oedema is treated with anti-VEGF injections at the site of the fluid build up. These are usually administered monthly until good vision is achieved. You may still need to have them on regular intervals. Injected steroid implants for macula oedema can also be used, they are repeated every 4-6 months. Sometimes a laser is used to seal any leaking blood vessels that are causing fluid accumulation at the macula.

Patients that have a retinal vein occlusion may go on to develop abnormal blood vessel growth on the retina and/or iris. The new abnormal blood vessels may then leak further blood or cause your eye pressure to rise significantly. New blood vessel growth is called neovascularisation. Treatment for neovascularisation is with Pan Retinal Photocoagulation (PRP) laser; whilst your vision will not improve it will preserve your remaining vision and stop new abnormal blood vessel growth. Patients with neovascularisation are monitored closely.