Eye Info

Childhood squint

Summary: Designed to help you understand more about your eye condition, this guide has been written by our experienced eye health team.

How the eye works

We need light to see what is around us and to see colour. Light bounces off the objects we look at. These reflect different amounts of light which we see as different colours.

  • 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 bends 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 focussing of this light.
  • Our tears form a protective layer at the front of the eye and also help to direct the light coming into our eye. The iris, the coloured circle at the front of our eye, changes the size of the pupil which allows different amounts of light into our eye. The pupil is the dark hole in the middle of the coloured part of our eye. The pupil gets smaller in bright conditions to let less light in and gets bigger in dark conditions to let more light in.
  • The middle of our eye is filled with a jelly-like substance called the vitreous. The vitreous is clear and allows light to pass directly from the front to the back of our eye.
  • 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 optic nerve is made up of thousands of nerve fibres. These fibres pass the electrical signals along to our brain where they are processed into the image we are looking at.

Seeing can be likened to the process of taking pictures on a film with a camera which you then get developed. The retina is like a camera film which stores an image of what we are looking at. The image directed onto the retina is then sent along to the brain where it is processed, like developing a camera film. Therefore, we actually 'see' in our brain with the light information sent to it from our eyes. This whole process happens very quickly so that everything we see is in focus.

What is a childhood squint?

A squint a problem when the eyes stop working together as a pair and therefore do not look in the same direction. One eye may turn inwards (most common in children), outwards or even upwards or downwards.

The medical term for squint is 'Strabismus'

A squint that turns inwards is called a 'convergent squint' or 'esotropia' and one that turns outwards is termed a 'divergent squint' or 'exotropia'.

What causes squints?

Squints are common and may affect up to 5 per cent of all children. Most children develop squints because they are long-sighted (problems with close-to focusing) and therefore need glasses.

There are other causes of squints some of which are not well understood. Occasionally a squint may occur in an eye that has poor vision caused by a problem affecting other parts of the eye such as cataract or damage to the back of the eye.

Some squints run in families, so if a parent has had a squint or needed glasses from an early age, there is an increased chance that their child may also be affected.

In rare cases an eye condition such as cataract or retinal problem may cause a squint.

When do children usually start squinting?

Most children begin squinting between the ages of 18 months and four years. This is a time when they are developing the ability to use their eyes together.

Some children begin to squint before the age of one year. This is a less common problem. The eyes tend to turn in towards one another and the angle of the squint is very large.

When children are born, the eyes and brains do not work well together, and over the first few months children may appear to squint every now and again, but this is usually nothing to worry about.

How does long-sightedness cause a squint?

Children have the ability to see things close up by over-focussing. Children who need glasses for long-sightedness need to focus even harder both for near and far distance. This over-focussing means that the eyes turn in towards one another and they go on to develop a squint.

How do squints affect sight?

The ability of the eyes and the brain to work together develops throughout childhood up to the age of about 8 years but particularly within the first two years of life. If a child develops a squint, the eyes stop working together and they stop developing the ability to work together correctly. Often one eye is 'switched off' to stop the child suffering from double vision. This may lead to a lazy eye (medical term 'amblyopia'), meaning that the vision in the squinting eye doesn’t develop and permanent loss of sight in that eye can occur. Unfortunately this cannot be fixed in later life so it is very important that squints are picked up early and treated.

How are squints found in children?

A squint may be noticed by parents, relatives, friends or health care professionals such as the health visitor or the GP. In some cases the squint may not be obvious, and the Government recommends that children are screened at nursery between their 4th and 5th birthdays prior to school entry, to ensure that their vision is good and that their eyes work together. However this may not happen in some parts of the country, and if you are in any doubt about whether your child's vision has been checked, then ask your GP or your health visitor for a referral to the orthoptist service in your area.

How are squints treated?

There are number of ways in which squints can be treated, children often need more than one form of treatment.

Glasses

All children with squint need to be tested for glasses and the majority will be prescribed a pair that they will need to wear at all times, otherwise a lazy eye may develop. Many do not need other treatment. Properly prescribed glasses give clear vision in both eyes, although some children are reluctant to wear glasses and may need a lot of encouragement. They often say that they can see better without the glasses and this is because they have been working their eyes so hard to focus that they find it difficult to 'relax' into the glasses to let them do the focussing for them. This usually settles but needs continuous wear of glasses.

Patching (occlusion)

Children who have a lazy eye (amblyopia) often require the good eye to be covered or patched (occlusion). This is done to make the lazy eye work harder. Patching should always take place when glasses are worn (in those who need them). Some children with a slightly lazy eye do not need patching, as the lazy eye improves with spectacle correction alone.

Exercises

In some cases exercises to strengthen the ability of the eyes to work together can be useful. This type of treatment is usually helpful in older children and is commonly used in association with glasses and or surgery.

Surgery

A small number of children require an operation on the eye muscles in order to straighten the squint. This is usually needed if the squint is very pronounced and is not improved by the proper correction of glasses. Sometimes surgery is performed on very young children.

Surgery is usually performed under general anaesthetic as a day case procedure. The operation usually weakens and / or strengthens the muscles of the eye so that the eyes are better aligned. Surgery will not improve the vision in a lazy eye.

After the operation it is usually necessary to continue to use glasses. Surgery may be carried out to help the eyes work together or it may simply be used to make the eyes look straighter (but not work together as a pair).

Botulinum Toxin injection

Children less than a year old who develop a squint may be offered treatment with an injection. This injection weakens the muscles that pull the eyes towards each other. This injection is carried out under general anaesthetic. This is a relatively new treatment for this condition and the injection may need to be repeated.

Who looks after squint?

There are three main professionals that look after children with squints: Orthoptists, Ophthalmologists and Optometrists.

Orthoptists are the experts in squints, double vision and amblyopia. They are extremely skilled in testing vision in young children and diagnosing squints. They are the people that are seen most regularly about a squint. They prescribe patching therapy, and consider the best use of glasses and any exercises that may help. They will help to monitor a child’s progress and often work closely with the ophthalmologist to check that treatment is working.

Ophthalmologists are hospital based eye consultants. They perform any surgery that may be needed. They also test sight and prescribe glasses that may be needed.

Optometrists (opticians) are experts at testing vision and prescribing glasses. They are also qualified to detect eye conditions or problems and can refer someone on to an ophthalmologist or orthoptist if necessary.

What are the outcomes of having a squint?

Most children are picked up and treated early with glasses (and patches in some cases) do extremely well and achieve good vision in each eye in the long-term. This is particularly the case is the problem is picked up early.

If a squint is not picked up before the age of 7 or 8 then it can have a serious permanent effect in one eye (amblyopia) which cannot be made better in later life.

Are there any support groups for people with squints?

As far as we are aware there is no support group for people with squints. There is an organisation for people with sight in one eye which may be useful for people with a lazy eye (amblyopia), although it must be stressed that amblyopia does not cause any problems for children / adults who have it. They are totally 'adapted' to their lazy eye (which may retain a reasonable level of vision).

One Vision
Wardington Court
Welford Road
Northampton
NN2 8AG

Tel: 0845 108 3161 (local call cost)

British and Irish Orthoptic Society
Tavistock House North
Tavistock Square
London
WC1H 9HX

Tel: 0207 387 7992

Provides information for lay or professional persons including information leaflets in download format.

What's next?

Our Adapting to sight loss page gives information useful for people with a newly diagnosed sight problem.

If you need more information contact our Helpline on 0845 766 9999 or 020 7388 2525 / helpline@rnib.org.uk - calls are charged at local rates.

RNIB does not comment on every trend or development but, when a treatment becomes established / recognised, we revise our website material to include it.

Unfortunately, RNIB can only answer email enquiries from the UK. But you may find an organisation for people with poor sight in your country through our agencies database.

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Content author: eyehealth@rnib.org.uk

Last updated: 06/03/2008 15:41

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