Good Hope Eye Department

Good Hope Hospital Eye Clinic
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Retinal vein occlusion     David Kinshuck
What is a retinal vein?

The retinal veins are the small ‘pipes’ in the retina that drain blood out of the retina, back to the heart.
cut through diagram of eye, showing arteries and veins the veins of the retina may block

this is a side 'cut through' diagram of an eye

(click to enlarge)

The retina is the thin film that lines the back of the eye, similar to the film of a camera. It is the part of the eye that makes us see. Light (things that you see) enters in through the front of the eye and falls on the retina.

The retina turns the light into electrical signals that are sent to the brain, allowing you to see. 

The veins drain the blood out of the eye, whilst the retinal arteries are the small pipes that deliver the blood (from the heart) to the retina, shown in red in these diagrams. These arteries deliver the blood to the whole of the retina.

  

 

What is a retinal vein occlusion?

A retinal vein occlusion is a blockage of one of these veins. The vein blocks when blood in it stops flowing; then the vein cannot drain the blood out of the retina.

When the vein blocks some blood leaks out. In addition, clear fluid leaks out causing ‘water-logging’ the retina. This naturally damages the sight.

 

 

Where does the vein block?
It is that blood flowing through the vein may be blocked by something pressing on the vein. For example, any condition, such as high blood pressure for many years, that makes the small arteries ‘hard’, may cause the artery to press on the vein and block it. In a branch retinal vein blockage, the blockage is along the course of a retinal vein:  

A view of the retina from the front: what the doctor sees looking into your eye.

The blue dotted line points to an artery—vein crossing point, where the vein may be blocked in 'branch retinal vein occlusion'.
 

front view of eye showing artery/vein crossing point
side view of eye showing artery/vein crossing point
 enlarge

 

In a central retinal vein occlusion, the blockage is at the optic nerve:
central retinal vein occlusion, flow obstructed at optic nerve central retinal vein occlusion, flow obstructed at optic nerve

 

When is your sight affected?
The centre of the retina is responsible for your sharp vision, such as seeing people’s faces or watching television.

If this central part of the retina (a tiny yellow spot in these diagrams) becomes ‘waterlogged’ by leakage from the blocked vein, your sight will be reduced.

After approximately 3 months, if the waterlogging remains, laser treatment may help to seal any leaks.

 retina, what the doctor sees, fovea

 

Factors that contribute to retinal vein occlusion
High blood pressure

Controlling the blood pressure helps to prevent the arteries getting ‘harder’, and can prevent a blocked vein in the other eye. Some experts now believe a blood pressure below 140/80 will not only help prevent a second occlusion, but help reduce any retinal leakage from the one present already.
High blood pressure triples the risk of a retinal vein occlusion, see

For information about blood pressure, visit
nhsdirect.

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Too much fat in the blood

A healthy diet helps. The Department of Health (& World Health Organisation) recommends people can help themselves by having a balanced diet including:
  • five portions of vegetables or fruit every day
    ...this is likely to reduce a recurrence by about 20%, see
  • eating small amounts only of animal fat (meat, dairy food)
  • salt: too much may contribute to blood pressure
  • 2 portions of fish such as salmon or tuna a week
  • 30 minutes exercise a day (eg walking, swimming)

Some experts recommend that many patients should use 'statin' tablets to lower their cholesterol, as this will aslo prevent heart and other diseases. (However, fibrates are preferable if the fasting triglyceride level is high.)

Obesity quadruples the risk of a retinal vein occlusion, see

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Smoking This hardens all the arteries. The more you smoke, the more damage is done. Try to stop: ask your GP or nurse if you need help. See

Smoking also contributes to cataracts, causing 25% of cataracts in the UK overall, and also 30% of macular degeneration.

Smoking triples the risk of a retinal artery occlusion and carotid artery narrowing (and carotid artery narrowing is much more common in retinal vein occluson patients, see)

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Glaucoma, diabetes, and other conditions

Other conditions may also cause a blockage of a retinal vein (retinal vein occlusion, RVO), and extra treatment may be needed. Your doctor will check that you do not have one of these conditions. Sometimes the cause is not found.

Patients with glaucoma who develop an RVO need to have a lower eye pressure. Patients with intraocular hypertension  need to be treated as though they have early glaucoma, and need a low pressure.
Oral contraceptive pills should be stopped.
If you are using hormone replacement therapy and have a retinal vein occlusion, some experts advise generally this should be stopped.

High fibrinogen levels in the blood contribute to retinal vein occlusions, and these may be increased by stress or unhappiness, see

If you are young or have had other venous occlusions, a check for other conditions may be needed. These include antiphospholipid antibody syndrome, factor V Leiden, or less commonly factor 5 or S abnormalities. For medical details see. Younger patients may need systemic steroids.

  

 

Types of retinal vein occlusion

 

A small ‘branch’ retinal vein occlusion

If the central area of retina, the macula (shown in yellow) is not affected, the vision may be completely normal. The red marks show the 'haemorrhages' in the retina.

See a photo.

 

enlarge

 small branch retinal vein occlusion, click to enlarge
A more severe ‘branch’ retinal vein occlusion

Inevitably the central part of the retina is affected, reducing your sight, and laser is often needed. Laser treatment may be needed to reduce waterlogging, stabilising the sight.

See photo (from mrcophth.com) and photo and larger  and RVO case with large photos

enlarge

 medium retinal vein occlusion, click to enlarge
A central retinal vein occlusion

Unfortunately, your sight is usually affected in this type of blockage. (Although a very mild blockage may not affect your sight.) Laser treatment does not improve the sight, but it may be necessary to prevent complications: tiny blood vessels can grow where they should not, leading to bleeding later. For medical details see.

If the blockage is severe, a lot of laser is needed to prevent severe glaucoma (animation here).

See photo (eyeatlas.com)

enlarge

 central retinal vein occlusion, click to enlarge

 

Retinal leakage

 

 some patients need treatment to reduce waterlogging of the retina
(shown here exaggerated)

enlarge

 

A retinal artery macroaneurysm
This occurs when one of the tiny retinal arterioles at the back of the eye block. A widened segment appears at the site of the blockage, and this may start to leak.
This is not really a retinal vein occlusion, but the causes are similar (hardening or the retinal arterioles), and it sometimes looks similar.
Here is a photo  and another in 2002 & 7 and close up. 		 

 

What is laser?
‘Laser’ is a very bright, but very narrow, beam of light. You need to sit in a machine like the one used to examine your eye, and the light is shone in through a small contact lens.
If your condition is mild, the laser treatment does not usually hurt.

(see Laser)

LASER is simply a highly focused and powerful light, where the light rays are all of the same type.  For this reason it can be pointed at one spot very accurately.

side view of eye showing retinal laser

Laser light (yellow) is shone into the eye through a small contact lens, and makes small burns on the retina.

 

New treatments, including Avastin
There are new treatments being developed.
  • One of these is an injection of steroid in the eye. Results are variable, and sight may only be temporarily improved. Different authors quote different results.
  • Avastin,   another injection into the eye, is likely to be extremely helpful, but is not yet available on the NHS. It is an-antigrowth factor (anti-VEG) drug. VEGF is released from the damaged retina, and it makes other areas of the retina leak etc. The leak in the macula area causes loss of sight.
    Avastin reduces the leakage and usually improves the sight if given at an early stage. However, the leakage starts again about 3 months later and often more injections are needed.
    Avastin is not yet licensed for this use...it may prove very helpful, but it is too early to say for certain. It does not seem to work well if unless the sight has only recently got worse.
 

 

What can you do?
  • A healthy diet and regular exercise can help. Lots of vegetables and fruit (five 100gm portions a day), and fibre may help, with the minimum of animal fat, dairy food, and salt. Exercise, such as walking or swimming, 30 minutes a day minimum is also recommended (Department of Health).
  • Aspirin may help to prevent further blockages, and it also helps to prevent heart disease. Ask your GP. There are alternatives to aspirin if you have a peptic ulcer or indigestion (clopidrogel). Your GP will need to adivse if you have very high blood pressure.
  • 'Statin' drugs may help. Ask your doctor.
  • If you have glaucoma, the eye pressure still needs treatment. If you have diabetes, you need to keep your sugar controlled and your blood pressure below or equal to130/80.
  • Generally patients who have had a retinal vein occlusion need their eyes examining by an ophthalmologist for two years to determine whether or not laser is needed. Patients with a minor blockage may not need many examinations, and those with a severe blockage may need a longer follow up. Once discharged from the hospital or clinic, see your optometrist every year for checks.
  • Without treating risk factors as above, 9-14% patients develop a second occlusion, with less than 4%. This also ignores the heart and stroke problems that can be prevented.
  

 

How to cope with poor vision in one eye
Ask your eye clinic doctor and optometrist, and see  Coping with poor vision and Coping with poor vision in one eye.  

 

Leaflet download

If you are a health professional and want to have a leafet to give to patients, instead of this web page, see 200k Adobe PDF

Alternatively, this is a Microsoft Publisher document click here, and you are welcome to download it and print copies. You are welcome to make changes for your patients (you can edit the leaflet in Microsoft Publisher).

You will need M Publisher 2000 to open and print the document. M Publisher is bundled as part of Microsoft Office. The only condition is that you let me know if there are any errors.
The document is 350k. The document can be printed out and photocopied to provide a double-sided leaflet 1/3 A4 size for your patients. The address is http://www.diabeticretinopathy.org.uk/leaflets/rvoweb.pub

----------------------Eye pages website feedback -----this page edited June 2008----------------------