A retinal vessel occlusion is a blockage in the blood vessels of your eye that can cause sight loss. There are two types of retinal blood vessels, arteries and veins, and either of these can be affected by an occlusion. This information describes these two different types of vessel occlusion and their affect on vision.
Light rays enter the front of our eye through the clear cornea and lens. It is very important that both the cornea and lens are clear as this allows the light to pass directly through the front of the eye to the retina. The cornea and lens bend light so that it can focus on the retina at the back of our eye. This gives us a clear, precise image. The cornea focuses the light towards our retina. The lens fine tunes the focusing of this light.
The retina at the back of the eye is a light-sensitive layer which consists of rod and cone cells. These cells collect the light signals directed onto them and send them as electrical signals to the optic nerve at the back of our eye.
Rod cells are concentrated around the edge of the retina. They help us to see things that aren't directly in front of us, giving us a rough idea of what is around us. They help us with our mobility and getting around by stopping us from bumping into things. They also enable us to see things in dim light and to see movement.
Cone cells are concentrated in the centre of our retina where the light is focused by the cornea and lens. This area is called the macula. Cone cells give us our detailed vision which we use when reading, watching TV, sewing and looking at people's faces. They are also responsible for most of our colour vision.
The retina at the back of your eye requires a constant blood supply. This blood supply makes sure that the cells of the retina get all the nutrients they need to continue working. While these retinal cells are working they produce waste and the blood supply removes this which keeps the retina healthy.
Like the rest of your body, there are two main types of blood vessels dealing with your eye's blood supply - arteries and veins. Arteries carry fresh blood from the heart and lungs to your eye and veins take away the blood that has been used by the eye and return it to the lungs and heart to be refreshed with oxygen and other nutrients. This process happens every time your heart beats so there is a constant stream of fresh blood and nutrients reaching all the cells in your eye. The arteries and veins in your eye are smaller than in other parts of the body but they do the same job.
It is possible for arteries and veins to become blocked and this can lead to medical problems. These blockages can happen throughout the body. When an artery or a vein that supplies the retina becomes blocked it is known as either a retinal artery occlusion or a retinal vein occlusion.
If you have been diagnosed with a retinal vessel occlusion but are unsure whether it affects a vein or an artery then your GP or ophthalmologist should be able to tell you which type of blood vessel has been involved.
The main cause of retinal artery or vein occlusion is atherosclerosis. Atherosclerosis is a problem with the condition of the inside of the blood vessel's wall. Blood vessels are like tubes with the blood flowing smoothly through them. Atherosclerosis is a problem with the inside of the tube. The tube is usually wide and smooth so that the blood flows directly through it. However in some people the inside of this tube becomes narrower or sticky which means it is harder for the blood to flow through it. These patches of stickiness on the inside of the blood vessels are called atherosclerotic plaques or sometimes hardening or thinning of the arteries and veins.
If you have sticky patches in your blood vessels they can catch any debris in your blood which in turn makes the plaques bigger. Eventually these plaques can become large enough to cut off part or all of the blood going to or from your retina. Large pieces of debris can also get caught and block off the blood vessel completely. If your retinal blood supply is affected in this way then you will have a retinal artery or vein occlusion.
There are a number of risk factors for thinning of arteries and veins which may lead to retinal vessel occlusion:
Nothing can be done about age but all the other risk factors can be controlled. Your GP can diagnose any circulation problems like high blood pressure and cholesterol levels and prescribe any medication to help control them. If you are diabetic then good diabetic control can help reduce the risk of blood vessel problems. A healthy diet and stopping smoking can all help to reduce the risk of you experiencing a retinal vessel occlusion. Your GP can give you advice on maintaining a healthy weight and stopping smoking.
Your retinal arteries provide the retina with the constant supply of fresh blood it needs to work properly. If the arteries become blocked then this fresh blood cannot reach the retina cells as it should. When this happens the retinal cells quickly suffer from the lack of fresh oxygen contained in the blood. This stops them working and sight can be affected quite quickly. A retinal artery occlusion will cause you to lose part of your sight. The amount of sight that is affected varies according to the location of the blockage.
The blood vessels which supply the retina spread across it like a tree. The retinal arteries have a large trunk of a blood vessel that splits into smaller branches to feed all parts of the retina. If the trunk of the tree is blocked then a lot of your sight your will be affected. This type of occlusion is called a 'central retinal artery occlusion'. If the blockage happens further along in one of the branch arteries then less of your sight will be affected. This type of blockage is called a 'branch retinal artery occlusion'.
The retinal veins drain away the used blood from the retinal cells. When one of these veins becomes blocked then the used blood cannot drain away properly. This causes the blood to 'back- up' in the system. This blocking and pooling of blood can cause the area to swell and may also cause areas of haemorrhage (bleeding). These areas of swelling and backed up blood damage the cells of the retina and therefore damage sight. Again the extent of the sight loss depends on where the blockage takes place. If the blockage is in one of the larger veins in the eye then it is called a 'central retinal vein occlusion'. If it is in one of the small retinal veins it will be called a 'branch retinal vein occlusion'.
Both retinal vein and artery occlusions cause a painless loss of vision. Both of them usually only affect one eye.
If you have an artery occlusion, sight is normally lost very suddenly with little or no warning. Some people may experience short periods of sight loss for a few seconds every now and again, before they experience a more permanent loss of vision. If you are experiencing short periods of sight loss with sight returning after a few seconds you should have your eyes examined as soon as possible. If you suddenly lose vision in one eye, you should attend your local accident and emergency department as soon as possible.
If you have a retinal vein occlusion your sight loss may be gradual, rather than sudden. You may notice your sight in one eye dims over a period of days eventually leaving you with very poor vision. If you experience any change in your vision you should have your eye examined as soon as possible either by an optometrist or, if the sight loss happens quite quickly, by your local accident and emergency department.
Unfortunately there is no treatment available for retinal artery occlusions. The cells on the retina are very sensitive to a lack of blood supply and a disturbance for any length of time in fresh blood to the retinal cells can cause permanent sight loss.
For some people the blockage that causes the sight loss may become dislodged, and if the blood supply is started again then some improvement in vision may be seen. However, most people have permanent changes in their vision.
The sight loss caused by this kind of occlusion can sometimes improve on its own. Some of the changes to your vision may be caused by the swelling and bleeding the blood backing up causes. If this swelling improves and the blood that has leaked is reabsorbed then you may notice an improvement in your sight.
There are three current treatments which can be used for macular swelling caused by retinal vessel occlusion: laser surgery, treatment with steroid injections and injections of anti VEGF medications.
In a few but not all cases a laser can be used in this type of occlusion to help control bleeding and swelling, and can mean that sight improves a little. Often the laser is also used to stop more damage occurring, so although no sight is restored the likelihood of losing more sight is reduced.
Sometimes steroids can be used to help control the swelling in the macula area. These can be given over a number of months or sometimes the ophthalmologist will use a steroid implant which will last for longer in your eye. These treatments can often be used when it isn't possible to use laser treatment.
Anti VEGF injections will help to reduce swelling in the macula area. These injections are given into the eye over a number of months. They have been shown to be effective in reducing swelling caused by a retinal vein occlusion.
Sometimes a retinal vein occlusion can cause new blood vessels to grow around the centre of the retina (macula). If this happens then it can affect your sight quite badly. The ophthalmologist may well recommend that you are seen in the clinic over the following months to check that this isn't happening. If new blood vessels do start to grow then sometimes they can be treated.
Laser can be used to seal of the new blood vessels that sometimes grow with this complication. This means that the swelling can be avoided. Unfortunately the laser can't be used very close to the macula area, so sometimes it isn't possible for everyone to have this treatment. Anti VEGF injections also stop new blood vessel growth.
Your ophthalmologist will discuss with you if you need treatment and which treatment they would recommend for you.
Retinal vessel occlusions are fairly common but there are ways of avoiding the chances of having one. Regular checks with the GP can discover whether you may be at risk and if so treatment can be given to improve your chances of not having an occlusion. Drugs to control high blood and cholesterol levels can help, and a good diet low in fat and saturated fat, stopping smoking and moderate exercise can all help avoid circulation problems that can be the root of the retinal occlusion. You can always ask you GP about steps you can take to make sure you are doing the best to keep your heart and circulation as healthy as possible.
Since retinal vessel occlusions are often connected to other more general circulation problems such as high blood pressure, high cholesterol levels or diabetes, then the ophthalmologist may want to check that your heart and blood are healthy. They may want to check your blood and your blood pressure and if they find any problems with this then they will suggest to your GP that they take steps to help with these problems. These may include taking aspirin to help 'thin' the blood, drugs to lower blood pressure if it is high and sometimes drugs to lower the cholesterol levels in your blood. All these steps can improve your circulation and so avoid the chance of having a similar occlusion in your other eye. It is therefore very rare for retinal occlusions to occur in both eyes.
Retinal vessel occlusions come as a shock to most people. The sudden loss of vision can be upsetting and it is quite normal to feel upset and worried at the time. However because usually the sight loss is contained to one eye people can quickly adjust to their new level of vision.
At first you may find that you are constantly aware of the change in your vision and that the sight loss in one eye dominates your vision making it difficult to see using both eyes. However after a few months you will probably find that this becomes less of a problem. This happens because our brains are able adjust to a new level of vision and are able to make the eye with good sight the dominant one. Usually, people find that with time their good eye 'takes over' and that tasks that were difficult become easier.
If a lot of sight in one eye is affected quite badly then for a period of time people may feel slightly unbalanced. This is because we are used to having pictures from two eyes to help us make sense of the world. When sight in one eye is affected it can affect our depth perception. You may find that you have trouble judging distances, how high a step is or how far away a table is. With time you should be able to judge these distances better but you should take care in the first couple of months.
You may be concerned about driving following loss of sight in one eye; however it is legal to drive with sight like this. As long as your sight in the other eye is good enough to see a number plate at 20.5 metres wearing any glasses that you may need and you have 120 degrees in your field of vision you will be legally able to drive. Your optician or ophthalmologist will be able to let you know if your sight is good enough for driving. You may be more comfortable waiting until your good eye becomes more dominant, but legally if you have good sight in one eye you are able to drive.
If you have an eye condition in your other eye that affects your vision then your sight loss may be more serious. You may find it useful to contact your local low vision clinic, social services department and local organisations for people with poor sight. They will be able to offer you advice and support on coping with poor vision and also be able to tell you more about the services and benefits for people with sight loss.
If you have lost some sight in both your eyes you may find your sight isn't as good as it was but there are a lot of things you can do to make the most of this remaining vision. This may mean making things bigger, using brighter lighting, or using colour to make things easier to see.
Ask your ophthalmologist, optometrist or GP about low vision aids, like a magnifier, and ask for a referral to your local low vision service. You should also ask whether you are eligible to register as "sight impaired" (partially sighted) or "severely sight impaired" (blind). Registration can act as your "passport" to expert help and sometimes to financial concessions. Even if you aren't registered a lot of this support is still available to you.
Local social services should also be able to offer you information on staying safe in your home and getting out and about safely. They should also be able to offer you some practical mobility training to give you more confidence when you are out.
Our Helpline can also give you information about the low vision services available, schooling, work and employment and our website offers lots of practical information about adapting to changes in your vision and products that make everyday tasks easier.
Being diagnosed with an eye condition can be very upsetting. You may find that you are worried about the future and how you will manage with a change in your vision. All these feelings are natural.
Some people may want to talk over some of these feelings with someone outside their circle of friends or family. RNIB can help, with our telephone Helpline and our emotional support service. Your GP or social worker may also be able to help you find a counsellor if you think this would help you.
The Macular Society has local groups which meet throughout the country and also offer a telephone counselling service. Sometimes it can help to talk about your feelings or share your experience with people who may have had similar experiences.
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