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 your 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 your retina.

Coats' disease usually occurs in children or teenagers under the age of 18 but most often before the age of 10. It affects boys more than girls, and 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 lines the inside of your eye. Your retina converts the light into electrical signals that travel along the optic nerve to our brain. The brain interprets these signals so we can "see" the world around us. 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 your retina called the macula, which is about the size of a pinhead. This highly specialised part of your 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. The macula also gives you much of your ability to see colours. The rest of your retina gives you side vision (peripheral vision). The eye is filled with a clear substance called the vitreous gel. Light passes through the gel to focus on your macula.

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. The cells of your retina need to remain healthy as your vision depends on this.

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 your vessels and into your retina. This fluid, known as exudate, builds up in your retina and causes it to become waterlogged (oedematous).

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

Most children with Coats' disease don’t have any symptoms – the eye does not look unusual, is not painful or red, and your child will not usually be aware that 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 like 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 may affect your child’s vision will depend on where in the retina the leaking blood vessels grow. In the early stages of Coats’ disease peripheral (side) vision is more likely to be affected. Peripheral vision describes what you see at the side when you are looking straight ahead.

Coats’ disease may progress and as more of your 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 their 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 it can cause the retina to detach from the back of the eye which can cause loss of sight.

The stages of Coats’ disease

Coats’ disease has 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 with increased effect on the retina and changes in vision.

Stage 3: Retinal detachment caused by large areas of exudation. This is when the vision is likely to be poor.

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

Stage 5: Usually at this stage an 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’s 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 your child 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. It’s normal for your child to feel that the light is too bright and that it’s uncomfortable, but it’s reassuring to know that it will not cause any damage to your child’s eye.

Sometimes the ophthalmologist may want to perform another test known as a Fluorescein Angiogram. A dye will be injected into a blood vessel in your child's arm, which travels through their blood stream to their eye. When the dye reaches their eye a series of photographs will be taken which will show the blood vessels of their retina filling with the dye. The ophthalmologist will be able to see if any of these capillaries are leaking because of Coats’ disease from these 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 children 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 to help prevent further changes to your child’s sight.

The treatment which your child's ophthalmologist may recommend depends on where and how much of their retina has been affected. The treatments used for Coats’ disease are laser photocoagulation and cryotherapy (laser 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 more advanced stages of Coats’ disease, the retinal capillaries will 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. The treatment will be aimed at reattaching the retina and will vary depending upon how large the detachment is and how long the retina has been detached for.

The recent research for the treatment of Coats’ disease has looked at the possible use of anti-VEGF drugs, which 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 is 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 may need to be done before they can be used routinely for everyone with Coats’ disease.

In the long term

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 more 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.

The effect that Coats’ disease will have on your child’s sight will depend on the age your child is when it’s first diagnosed. Being diagnosed early when the capillaries are only showing slight changes would mean that there are more treatments available to your child, like laser photocoagulation or cryotherapy. 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 suitable.

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. It’s reassuring to know that 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 can 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 your child couldn't hold a Heavy Good Vehicle or Public Service Vehicle licence. Some professions, such as being a pilot, policeman or some areas of the forces require a certain level of vision to be reached in both eyes. Keeping this in mind can help you and your child plan their career choice for the future.


It’s completely natural to be upset when your child has been diagnosed with Coats’ disease and it’s normal to find yourself worrying about the future and how your child will manage with a change in their vision.

It can sometimes be helpful to talk over some of these feelings with someone outside your circle of friends or family. At RNIB, we can help with our telephone Helpline and our Emotional Support Service. You may also find your GP or social worker can help you find a counsellor if you feel this might help you.


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