- The retina, arteries and veins
- The fovea
- What is a retinal vein occlusion?
- Where does the vein block?
- The sight is affected by retinal oedema (leakage)
- Factors that contribute to retinal vein occlusion
- Small 'branch' retinal vein occlusion
- More severe 'branch' retinal vein occlusion
- Hemispherical occlusion
- Central retinal vein occlusion
- A retinal macroaneurysm
- Treatment of retinal vein occlusions
Retinal vein occlusion (RVO)
David Kinshuck
The retina, arteries and veins
The retina is the 'film' at the back of the eye, like the film of a camera. Light enters the front of the eye and passes onto the retina, which turns the light into electrical signals. These are sent on to the brain, allowing us to see.
Blood flows into the retina in small arteries, shown in red in these diagrams. The blood then passes flows out in tiny veins (blue in the diagrams here).
The fovea
The fovea is the centre of the retina. All the light is focused at the fovea. As a result, damage to the fovea will reduce the sight more than damage elsewhere in the retina. In these diagrams the fovea is marked with a yellow spot in the centre of the retina.
A
view of the retina from the front: what the doctor sees looking into
the eye.
The retinal veins are blue, and the arteries red. The yellow spot is the fovea, the centre of the retina.
enlarge
A retinal vein occlusion (RVO)
A retinal vein occlusion is a blockage of one of these veins. The vein blocks when blood in it stops flowing. The blocked vein then leaks blood leaks out, causing the haemorrhages.
The retina around the vein becomes damaged, and clear fluid
leaks out causing 'water-logging', called 'oedema'.
The oedema and haemorrhages reduce the sight.
Where does the vein block?
High blood pressure for many years damages the arteries, making then 'hard'. The hardened artery seems to press on the vein and block it. Depending on the site of the blockage, there is a different type of vein occlusion.
The blue dotted line points to an artery...vein crossing point, where the vein may be blocked.(enlarge)
In a central retinal vein occlusion, the blockage is at the optic nerve (enlarge). In a branch occlusion, the blockage is further out.
If the artery is closer to the vein, occlusion is more likely (enlarge). Eye 17
The sight is affected by retinal oedema (leakage)
Retinal oedema animation
The damaged retina leaks, like a waterlogged sponge, which we call 'oedema'.
The central retina is responsible for sharp vision, such as seeing people's faces or watching television. If the oedema damages affects the central retina the sight will be particularly reduced, and it will not be possible to see details such as reading or seeing faces easily.
The oedema may be caused by any type of RVO.
If the central part of the retina, the fovea, becomes 'waterlogged' by leakage from the blocked vein. See left explanation and right explanation
Factors that contribute to retinal vein occlusion (RVO)
| Contributions to retinal vein occlusions |
|---|
|
We do not know exactly how an occlusion occurs, but do know the problems that contribute, the 'causes'. These factors need to be addressed by patients in order to prevent a second occlusion, as below. Sometimes no cause is found.
A high cholesterol may be caused by
- a poor diet
- genes inherited
- diseases such as diabetes and uncontrolled thyroid problems
Less commonly. other conditions may also contribute
- Oral contraceptives and hormone replacement therapy
- High fibrinogen levels in the blood contribute to retinal vein occlusions, and these may be increased by stress or unhappiness, see
- high homocysteine (genetic, poor diet)
- If you are young or have had other venous occlusions, a check for other conditions may be needed. These include anti-phospholipid antibody syndrome, factor V Leiden, or less commonly factor 5 or S abnormalities. For medical details see.
- risk of stroke Ophth15
Types of retinal vein occlusion
There are various types of occlusion.
A small 'branch' retinal vein occlusion
A branch RVO is due to compression from an adjacent retinal arteriole, related to hypertension etc. See
A small occlusion: vision is reduced only if the central retina becomes oedematous enlarge
A more severe 'branch' retinal vein occlusion
A larger area of retina is affected. Often the central part of the retina, the fovea, is affected, reducing the sight,
25% of the retina can be affected with oedema and haemorrhages. photo and larger .
Anti-VEGF drugs and occasionally laser may help, as below.
a branch retinal vein occlusion with lots of haemorrhages enlarge
A hemispherical RVO
a hemispherical retinal vein occlusion with lots of haemorrhages enlarge
A larger occlusion more common in glaucoma patients, 50% of the retina is affected.
Laser treatment does not improve the sight, but it may be necessary to prevent complications: tiny blood vessels can grow on the retina etc, leading to bleeding later.
Anti-VEGF drugs and steroid injections as below may help.
A central retinal vein occlusion
Unfortunately, the 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. Anti-VEGF drugs and steroid injections as below may help.
If the blockage is severe, a lot of laser is needed to prevent severe glaucoma
(animation here) enlarge
A retinal macroaneurysm
A retinal artery macroaneurysm 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.
Treatment EJO 15.
If the macroaneurysm is leaking (?may be a retinal vein macroaneurysm) it can be lasered:
- if it leaks and the oedema threatens macula
- laser around the macroaneurysm
Treatment of retinal vein occlusions
These treatments are aimed at
- reducing the macular oedema and improving reduced sight
- reducing the risk of bleeding from new vessel growth on the retina or in the drainage angle of the eye as below
There is now a choice of treatments, often used in combination:
- medical treatment (discussed below)
- laser
- anti-VEGF injections
- steroid injections
- comparison EJO 15
Laser
Laser light (yellow) is shone into the eye through a small contact lens, and makes small burns on the retina.
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. Patients sit on a machine like the one used to examine the eye, and the light is shone in through a small contact lens.
If the condition is mild, the laser treatment does not usually hurt. More severe occlusions need heavier and more unpleasant laser.
If there is a large area of retina affected, there is a risk rubeotic glaucoma / posterior segment neovascularisation/vitreous haemorrhage, and laser will reduce this risk. 3 sessions of laser are often needed. Laser can reduced the macular oedema a little.
Anti-vegf treatment
These drugs are anti-growth factor (anti-VEGF) drugs. VEGF is a chemical released from the damaged retina in this condition, and the VEGF makes other areas of the retina leak, creating an on-going problem. These drugs are given as injections into the eye, but are not yet available in all departments in the UK. Anti-VEGF treatment is probably best is there is a smaller area of damage, steroid implants if larger areas are affected. BMJ 15 macular oedema strategies BRI15
The damaged retina releases VEGF, and this causes even more damage.
Anti-VEGF stops the secondary damage (red cross)
There are 3 drugs, two described here:
- Details about the procedure
- There is 1/1000 risk of a very severe infection
- Injections often have to be given on a repeated basis...each injection lasts a month, sometimes little longer.
- This treatment may not work if there is a lot of oedema (leakage)
- Avastin is probably just as good as the more expensive Lucentis.
- Lucentis is £650 just for the drug for each injection, Avastin <£100
- previsouly 3 injections are offered to start with, a month apart,
more anti-VEGF injections if oedema increases
- then patients are asked to attend for monthly OCT scans, and if the fluid increases, another injection is offered.
- The decision to inject is based on patients' wishes and the OCT scan..if there is macular oedema (leakage, as judged by the OCT scan) then an injection may help.
- Macula oedema (leakage near the macula) causes loss of sight, so the injections are helpful reducing the oedema and improving the sight
- branch RVOs: BRAVO
- Central: CRUISE Retina 2011
- one injection and then treat and monitor gives equal results Retina 17
- little difference between anti-VEGF and steroid injections below Eye 17.
Steroid injections
- Osardex is the main drug, and is a steroid implant
- steroid implant page
- It lasts 3-6 months, and again often needs repeating.
- There is 1/1000 risk of a very severe infection
- everyone gets a cataract (100%)
- ~10% serious glaucoma risk
- ~30% risk of mild glaucoma.
- Again, retreatment advice will be based on patients choice and macular oedema (leakage), as judged by the OCT scan.
- For the best results, treatment is best started as soon as possible after the occlusion.
- There are newer longer acting steroid implants.
- Steroids will be particularly helpful if a large area of retina is affected
- If there is a large area of retina affected, there is a risk rubeotic glaucoma / posterior segment neovascularisation/vitreous haemorrhage: a steroid implant will reduce this risk.
- Steroids work by reducing the inflammation: the retina damaged by the blocked vein becomes inflamed.
Risk of rubeotic glaucoma / posterior segment neovascularisation/vitreous haemorrhage
As above, if there is a large area of retina affected, there is a risk rubeotic glaucoma / posterior segment neovascularisation/vitreous haemorrhage: a steroid implant or laser will reduce this risk.
Risk of posterior segment new vessel growth & bleeding (neovascularisation & vitreous haemorrhage)
- 9% CRVO
- 8% BRVO
Medical treatment: what can you do?
Patients should try and reach the targets here:
- BP < 140/85 in clinic, BP < 130/80 at home
- cholesterol <4.0mmol/l
- HbA1c <6.0%
- 2 hours exercise a day
- women using contraception BMJ 15
High blood pressure
High BP contributes to many RVO. So controlling the blood pressure helps to prevent the arteries getting 'harder', and can prevent a blocked vein. high BP causes 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. The lower the blood pressure the better as long as you feel well. Treatment is outlined here.
A healthy diet
- five portions of vegetables or fruit every day ...this is likely to reduce a recurrence by about 20%, (five 100gm portions a day),
- eating small amounts only of animal fat (meat, dairy food)
- no transfats; or processed meat such as ham
- salt: too much may contribute to blood pressure
- 2 portions of fish such as salmon or tuna a week
- Plant sterols lower cholesterol: these are in pulses such as soya and probably others such as lentils and other beans and chickpeas, and Benecol products.
- Minimal salt
- Minimal alcohol (each unit of alcohol puts the blood pressure up 2.2mmHg.
- We need low homocycsteine levels...these are lower with a diet with plenty of vegetables. See how to lower levels.
Cholesterol
A low cholesterol is important, and healthy diet as above will help. Sometimes a healthy diet will lower the cholesterol enough. But if the cholesterol remains high despite the healthy diet, RVO patients generally need 'statin' tablets to lower their cholesterol. A cholesterol less than 4.0mmol/l is best, the lower the better. A low cholesterol will also prevent heart and other diseases. Fibrates are preferable if the fasting triglyceride level is high.
'Statin' drugs are generally needed if the cholesterol is >4.5 mmol/l, and there are no side effects. (25% of patients get side effects, which generally disappear when the drug is stopped). GPs can advise.
Obesity
Obesity quadruples the risk of a retinal vein occlusion, see.
Exercise
A minimum 30 minutes exercise a day (eg walking, swimming). 10000 stops or 2 hours walking a day preferred if overweight, 5000 steps/1 hour walking if a normal weight.
Smoking
Smoking with an RVO is highly risky, increasing the risk >300%, that is increasing the risk 3 times, and strongly not advised. The more you smoke,
the more damage is done see.
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 occlusion patients.
Glaucoma
If you have glaucoma, the eye pressure needs treatment, and a low eye pressure is needed.
Intraocular hypertension
Patients with intraocular hypertension need to be treated as though they have early glaucoma, and need a low pressure.
Aspirin
Aspirin may help to prevent further blockages, and it also helps to prevent heart disease. Patients should discuss with their GP. There are alternatives to aspirin if there is a peptic ulcer or indigestion (clopidrogel). GPs will need to advise if you have very high blood pressure. Aspirin may not help Ophth 2011
Diabetes
If you have diabetes, you need to keep your sugar controlled and your blood pressure below or equal to 130/80 in clinic.
If an RVO occurs in a patient with diabetic retinopathy,
the outcome will be much worse...much more leakage, and new vessel development
is much more likely. Eye 14.
Patients with diabetes are more likely to have high blood pressure, so this can lead to RVOs.
Sleep apnoea
This increases risk. Patients with sleep apnoea need treatment and need to lose weight Archives 2010 If you snore and have irregular breathing whilst asleep, you may have this condition: ask your GP.
Follow up and tests
- Generally patients who have had a retinal vein occlusion need their eyes examined 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, optometrist checks every year are recommended.
- 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.
- Blood tests are needed to check the blood count, the thickness of the blood, lipids, and HbA1c for diabetic (FBC, U&Es, lipids, CRP, HbA1c)
- Oral contraceptives and hormone replacement therapy 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, less commonly factor 5 or S abnormalities, homocysteine (if high: genetic, poor diet) For medical details see.
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.
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