Coats' disease

About Coats’ disease

Coats’ disease, also known as Exudative Retinitis, is an uncommon eye condition which affects the smaller blood vessels (capillaries) found in the retina – the light sensitive layer which lines the inside of your eye. Coats’ disease can make these blood vessels weak and grow incorrectly causing them to leak fluid and blood under the retina.

Coats’ disease usually occurs in children or teenagers under the age of 18 but most often before the age of 10. Coats’ disease affects boys more than girls. Most children with Coats’ disease only have the retinal changes in one eye.

How the eye works

When you look at something, light passes through the front of your eye and is focused by the lens onto your retina. The retina is a delicate tissue that coats the inside of your eye. The retina converts the light into electrical signals that travel along the optic nerve to your brain. The brain interprets these signals to “see” the world around you. The retina is supplied with blood by a delicate network of blood vessels on its surface and by a layer of blood vessels underneath the retina.

Light is focused onto a tiny area of the retina called the macula, which is about the size of a pinhead. This highly specialised part of the retina is vital, because it enables you to see fine detail when you are looking directly at something such as words, photos or the television. Your macula also gives you much of your ability to see colours. The eye is filled with a clear substance called the vitreous gel and light passes through the gel to focus on the macula. The rest of the retina gives you side vision (peripheral vision).

Coats’ disease and the eye

Coats’ disease affects the retinal blood supply, in particular the retinal capillaries. Retinal capillaries are important in supplying your retina with blood. Blood carries nutrients to the cells of your retina so that they work correctly. Your vision depends on the cells of the retina remaining healthy.

Coats’ disease causes retinal capillaries to develop incorrectly. They become wider (dilated) and twisted, which make them more noticeable when the inside of your eye is examined. The medical term for these changes is telangiectasia.

As well as the retinal capillaries becoming dilated, they also become weak and leaky. This causes some of the fluid from the blood to leak out of the vessels and into the retina. This fluid, known as exudate, builds up in the retina and causes it to become waterlogged (oedematous)

Where there are areas of exudates and telangiectasia, the retina will not be able to function correctly. This in turn will affect this area of vision.

Most children with Coats’ disease don’t have any symptoms – the eye does not look unusual, is not painful or red, and the child isn’t usually aware there is a problem.  Often children are diagnosed following an unusual finding at an optician’s appointment, after failing a school vision screening test, or when the eye has an odd appearance on photographs (usually a white/pale pupil rather than a red pupil when a flash photograph is taken).

Causes of Coats’ disease

The cause of Coats’ disease isn't yet known (this is medically known as idiopathic) but it doesn't appear to be hereditary (passed through families) or caused by any other health conditions.

Effects of Coats’ disease

How Coats’ disease affects vision will depend on where in the retina the leaking blood vessels grow. In the early stages of Coats’ disease peripheral vision is likely to be affected. Peripheral vision is also known as your side vision and describes what is seen at the side when you are looking straight ahead.

Coats’ disease may progress, and as more of a child's retina is affected, more of their vision will be affected. There is a small central area of your retina, known as the macula. The macula gives you your central and detailed vision. This is what you use when you look directly at something, for example when you read. If Coats’ disease affects the macula then your child's central vision will be affected.

In the advanced stages of Coats’ disease more vision will have been lost because more of the retina has been affected. When a large area of retina has become swollen by exudates it can cause the retina to detach from the back of the eye which will cause loss of sight.

The stages of Coats’ disease

Coats’ disease can be classified into different stages depending on how it is affecting the retinal capillaries and retina.

Stage 1: Telangiectasia only causing little change to the retina and vision.

Stage 2: Telangiectasia and exudation noted with increased effect on the retina and changes in vision.

Stage 3: Retinal detachment caused by large areas of exudation. The vision is likely to be very poor.

Stage 4: Complete detachment of the retina and the development of other complications, such as secondary glaucoma (raised eye pressure) which will be treated, although sight will be poor.

Stage 5: Usually at this stage the eye has no sight and no treatment is available to improve sight. In most cases the eye isn’t painful, but if it were treatment may be needed to prevent the pain or further damage to the eye.


An eye examination is the only way to tell if your child has an eye condition. Children can adapt very quickly to a change in their vision and there can be very few signs that they have any problems especially if only one eye is affected. All children should have their eyes screened when they start full time at school.

If you are concerned about your child's vision or their eyes it is important to have them checked by an optometrist (optician). They will be able to check any changes in the level of your child's vision and the health of their eyes. If the optometrist is concerned by anything they find during the eye examination, they will refer you to the eye clinic at the hospital.

At the eye clinic, your child's eyes will be checked by an eye specialist, known as an ophthalmologist. The ophthalmologist will put drops into your child's eyes which will make their pupils bigger. They will then shine a bright light into your child's eye to look at the retina. Putting in the eye drops means that the ophthalmologist has a better view when they are assessing their retina. Although the light used at the hospital is bright it will not cause any damage to the eye.

Sometimes the ophthalmologist may want to perform another test known as a fluorescein angiogram. This is where a dye is injected into a blood vessel in your child's arm. This dye travels through the blood stream to their eye. When the dye reaches their eye a series of photographs will be taken, these photographs will show the blood vessels of their retina filling with the dye. If any of these capillaries are leaking because of Coats’ disease the leaking will show up on the photographs.

These tests should let the ophthalmologist know if your child has Coats’ disease.


Coats’ disease can be treated to try and prevent further changes to your child's sight.

In the early stages of Coats’ disease there may be little or no effect to your child's vision. If this is the case the ophthalmologist may decide to monitor your child's eyes at regular appointments rather than do any treatment. In some cases Coats’ disease doesn't develop any further than stage 1.

In later stages, when the Coats’ disease has progressed and has had more of an affect on your child's vision, the ophthalmologist may decide to do some treatment.

The treatment which your child's ophthalmologist recommends depends on where and how much of their retina has been affected. The treatments used for Coats’ disease are laser photocoagulation and cryotherapy (using cold temperatures). The aim of both these treatments is to stop the retinal capillaries from leaking. Most children would have these treatments under a general anaesthetic.

In advanced stages of Coats’ disease, the retinal capillaries have leaked a lot and there will be large areas of exudates affecting your child's retina. These can cause the retina to detach from the back of the eye. Treatment is aimed at reattaching the retina and will vary depending upon how large the detachment is and how long the retina has been detached for.

Recent research for the treatment of Coats’ disease has looked at anti-VEGF drugs. These types of drugs can be used to prevent the development of new leaking blood vessels. These treatments are used regularly in adults for other eye conditions but their use in Coats’ disease is relatively new. Coats’ disease usually has to be treated on a very individualised basis and your ophthalmologist will be able to advise whether or not they would like to use anti-VEGF treatment for your child. At the moment this treatment is relatively new and is not available on the NHS, though your ophthalmologist may be able to arrange funding. A lot more research is needed before they are used routinely for everyone with Coats’ disease.


The effect of Coats’ disease on sight will vary from person to person. Generally the condition will gradually progress and affect more of the retina. For younger children, especially those under 3 years old, the changes to their retina tend to progress quickly, are difficult to control and are more likely to have a long term effect on visual development. In older children and young adults, Coats’ disease can have a much milder and slower effect on the retina. In many cases this progression may stop on its own accord and may not need any treatment.

When your child is diagnosed with Coats’ disease will have an effect on the prognosis for their vision. Being diagnosed early when the capillaries are only showing slight changes would mean that there are more treatments available to your child. Laser photocoagulation or cryotherapy are used in stopping Coats’ disease from getting worse. In some cases treatment can improve vision.

If your child has been diagnosed in the later stages of Coats’ disease, where large areas of the retina have already been affected, then laser photocoagulation or cryotherapy treatment may not be appropriate. If your child has had a retinal detachment, then there are different treatments available to help repair this. It is important that a retinal detachment is repaired as soon as possible, as this would help with how successful the treatment is.

Sometimes despite all treatment, the eye does not respond and may become blind. Typically the eye remains comfortable, but late complications such as cataract (cloudy lens) or glaucoma (raised pressure) may need treatment. Very rarely, if the eye remains painful if could be removed but this would be a last resort.

Most children with Coats’ disease do not have their eye removed.

Coping with sight problems

The amount of vision lost will vary between individuals. Coats’ disease usually affects one eye only (monocular vision) and children tend to adapt very well to using their better eye. This does not mean that they will be over using their better eye. It is unusual for children with good vision in one eye to need additional support in their education and they are not considered partially sighted.

Having monocular vision can affect your child's depth perception and hand-eye coordination. For some tasks your child may appear clumsy and uncoordinated at first, for example when they throw and catch a ball. This generally improves when your child gets older and adapts to being monocular.

Even with good vision in their better eye, your child doesn't have as much peripheral vision as someone with two eyes. With time they will adapt to this without realising by turning their head to see things in their peripheral vision. You could help your child by sitting or approaching your child on the same side as their good eye. This would make it easier for your child to see you.

These are difficulties your child may experience and you might find it useful to inform their nursery, school teachers or carers of these.

In the future your child would still be able to drive a private vehicle. As long as the vision in their remaining eye is unaffected by other eye conditions and they are able to achieve the visual requirements for driving. However monocular vision would mean you child couldn't hold a Heavy Good Vehicle or Public Service Vehicle licence. This may affect your child's career choice in the future. Some professions, such as being a pilot, policeman or some areas of the forces require a certain level of vision to be reached in each eye.


Having an eye condition diagnosed can be very upsetting. You may find that you are worried about the future and how you and your child will manage with a change in their 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.

Help to see things better

Support Organisations

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The RNIB Helpline can:

  • put you in touch with an RNIB specialist advice service such as welfare benefits and rights, education, employment, legal rights, emotional support, daily living help and residential care
  • send you free information and leaflets
  • give you details of support groups and services in your area.

Call us Monday to Friday 8:45am – 5:30pm on 0303 123 9999

Other sources of help

Look UK is an organisation which helps support families with children aged between 0-16 with vision problems. They have family support officers and help support families at home and in school. They can be reached at:

Look National Office
C/o Queen Alexandra College
49 Oak Court Road
B17 9TG

Tel: 0121 428 5038

National Blind Children’s Society (NBCS) can offer information, support and advice to parents and carers of children with sight loss or an eye condition.

Reading Road
Burghfield Common

Tel: 0845 372 7332
Family Support: 0800 781 1444

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