Childhood squint (strabismus)
Squint is an eye condition, where the eyes do not look in the same direction. This means that one eye may not focus on an object someone is looking at. Whilst one eye looks forwards to focus on an object, the other eye turns either inwards, outwards, upwards or downwards. Most squints occur in young children. Sometimes when a child has a squint, the sight in the eye which squints may be weaker than the sight in the eye without the squint. Squints can also develop in adults but normally for different reasons than cause them in young children.
Strabismus is a more medical term for squint and you may hear it being used by eye care professionals.
This page will take a look at childhood squints.
How the eye works
Your eye is shaped like a round ball. At the front of your eye is a clear tissue called the cornea, which allows light to enter your eye. Light is focused through the pupil which is a hole in the centre of the iris, the coloured part of your eye. Behind your iris is your lens, which also focuses the light coming through the cornea. Both the cornea and the lens focus the light coming into your eye onto an area of the retina (back of your eye).
Your retina is made up of a number of layers but the most important for vision is the layer made up of cells called photoreceptors. Photoreceptors are cells which are sensitive to light.
When light reaches your retina, the photoreceptors react to the light by sending a small electrical charge through the optic nerve to your brain. The photoreceptors react differently to different light levels or lighting conditions and this changes the nature of the electrical signals. When your brain receives these electrical signals they make sense of them and this provides you with the pictures that we call sight.
Your eyes work together as a pair. When you look at an object your eyes will be pointing in the same direction and focusing at the same point. Your brain will receive similar but slightly different pictures from each eye and joins them together to allow you to have binocular vision. The slight difference between the two pictures seen with each eye allows you to have depth perception which helps you to judge how far away things are.
The movement of each eye is controlled by six muscles that pull your eye in specific directions. The muscles for one eye also work and coordinate with the muscles from your other eye. This allows both your eyes to coordinate their movement together. A squint can develop when your eye muscles do not work in a balanced way and your eyes do not move together correctly.
Development of vision
When you are born, your eyes and brain do not work well together. As you grow you use your eyes and brain to see the world and this builds up a connection between them. This connection between the eyes and the brain is known as the visual pathway.
The visual pathway develops throughout your childhood and up to the age of about 8 years old. During this time it is important that your eyes send clear and similar images to your brain. The eyes and brain use your visual experiences to improve their coordination and how well you can see.
Squints are common and studies suggest that somewhere between 2-3 per cent of children will have a squint.
A squint is where one of your eyes points in a different direction from the other eye. This can be particularly noticeable when a child is making an effort to focus directly on something; although for other children the squint becomes more noticeable when they are NOT focusing directly on a task.
Causes of childhood squint
There are many different types of squint and for some children there will not be a particular cause for their squint. However some of the more common causes of squint are:
Refractive errors are conditions where there is a problem with the focusing power of the eye. They are usually corrected by glasses. The most common types of refractive error are:
- Myopia (short-sightedness): causes things up close to be clear and those in the distance to be out of focus and blurry.
- Hypermetropia (long-sightedness): may cause things both up close and in the distance to be blurry. Hypermetropia also causes the eye to work harder to see things close up.
- Astigmatism: causes blurry vision up close and in the distance and is caused by the front of the eye not being quite spherical (rounded).
Hypermetropia (long-sightedness) and sometimes myopia (short-sightedness) in children may cause a squint to develop where the eye turns in (esotropia).
Children's eyes have a lot of focusing power. This allows them to make the things they look at clear in the distance and up close. If your child is long-sighted their eyes will need to focus harder to make both their distance and close up vision clear. Some children are able to do this by over focusing. This can cause their eyes to turn in towards one another (esotropia) and they may go on to develop a squint. Having glasses to correct their hypermetropia (long-sightedness) makes their focusing more relaxed and gives clearer vision. At the same time the glasses may also straighten their eyes and remove the squint.
Some squints run in families so if a parent has had a squint or needed glasses from an early age there may be an increased chance that their child may also be affected.
Other eye conditions such as cataract or damage to the retina can cause the eye to have poor vision. This may also cause a squint to develop in this eye.
Children that are born early (before 32 weeks) may be at more risk of developing a squint.
Children with conditions such as cerebral palsy and Down's syndrome may also be more prone to develop a squint.
Describing the types of squint
Whatever type of squint your child has, it may be described in different ways by the professionals looking after your child’s eyes. Some of the words you may hear will have particular meanings when used to describe the squint and the squint may be described depending on:
- When it can be seen - constant, if it is visible all the time and intermittent if it comes and goes.
- When it is first noticed - infantile if it develops within the first 6 months of life and acquired if it occurs later.
- If it is caused by refractive error - refractive if the squint is caused by refractive error and non-refractive if it isn't.
- How the eye turns - if the turn is inwards it is called a convergent squint or esotropia, if the turn is outwards it is called a divergent squint or exotropia, if the turn is upwards it is called a hypertropia, if the turn is downwards it is called a hypotropia.
- Whether particular muscles are involved - incomitant if the squint changes when looking in different directions and concomitant where the squint is the same when looking in every direction.
This means that your child's squint can be carefully categorised by the professionals involved and they may describe your child's squint using a number of these words, for example, an "intermittent convergent squint". Knowing the nature of a child's squint and labelling it as accurately as possible can help to decide how it is dealt with.
When your child is born their eyes and brains do not work well together. Over the first few months you may notice their eyes appear to squint or move separately from each other every now and again. This is normal and usually should get better by around 2 months and should be gone by the time your child reaches 4 months. If this isn't the case then you should speak to your GP or health visitor about a referral for a full assessment with your hospital eye department.
More commonly a squint will develop a little later in your child's life often between the ages of 18 months and 4 years old.
The effect of a squint on vision
If your child develops a squint it means each eye is looking in a different direction and their eyes are sending different pictures to the brain. Their brain finds it difficult to merge the two pictures into one clear image because the pictures are so different. This means their eyes have stopped working together and can cause double vision. As your child's visual system is still developing the brain can easily adapt to stop this double vision. The brain will begin to ignore the pictures coming from eye which has the squint and they will use only the vision from their better/straight eye.
Children can easily adapt to using one eye and it may not be obvious from how they are acting that they have any problems with their eyes and vision. This may only be detected by having your child's eye tested by an eye health professional.
Amblyopia is caused when the visual system doesn't develop correctly in one eye, causing the vision to be blurred in that eye even when a child is wearing the correct glasses they need. An eye which has amblyopia can be called an amblyopic eye or a lazy eye.
A child with a squint can develop amblyopia in the eye which has the turn. This is called strabismic amblyopia.
Some children may have amblyopia, but they may not have a squint. This is referred to as refractive amblyopia and is caused by one eye needing a very different (glasses) prescription compared to the other eye. This eye may be a lot more short-sighted (myopic), long-sighted (hypermetropic) and/or have a high astigmatism.
Amblyopia can lead to a permanent reduction in how well this eye can see. There are different ways to treat an amblyopic eye and treatment is more successful when vision is still developing before the age of 7 or 8.
Unfortunately amblyopia cannot be fixed in later life so it is very important that squints or refractive amblyopia are picked up early and treated.
A squint may be noticed by parents, relatives, friends or Health Care professionals such as the Health Visitor or the G.P. The government recommends that your child’s vision should be screened between their 4th and 5th birthdays, around the time they start school to ensure that their vision is good and that their eyes work together. This service is usually managed and sometimes carried out by professionals known as orthoptists who detect and help manage any treatment needed for squints. Unfortunately this screening 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 they you should ask at your child's school or nursery.
If you are concerned about your child's eyes before this check, because you have noticed a squint or other symptoms, then you should discuss this with an optometrist (optician), your GP or your Health Visitor and ask to be referred to an orthoptist.
Professionals involved in looking after squint
There are three main professionals who will look after your child's squint: Orthoptists, Ophthalmologists and Optometrists.
Orthoptists are usually based in the eye clinic at the hospital and are recommended to carry out or manage the children's screening service. They are experts in how the two eyes work together (known as binocular vision) and this includes squints, double vision and amblyopia. If your child is suspected to have one of these conditions, they are usually one of the first professionals they will see if they are referred to the hospital. Orthoptists are extremely skilled in testing vision in young children, diagnosing squints, prescribing patching therapy and any eye exercises that may help. Most of your appointments about your child's squint will be with an orthoptist.
Ophthalmologists are hospital based eye consultants. Their job is to diagnose eye conditions and perform any treatment or surgery that may be needed. If your child has been referred to the hospital for a squint, they may see an ophthalmologist to check the health of the eyes and make sure there is no underlying eye condition causing the squint.
Optometrists (Opticians) are experts at testing your vision and prescribing glasses. They are also qualified to detect eye conditions or problems, including squints and binocular problems. If your child is prescribed glasses to help treat their squint then you may see an optometrist on the high street or in the hospital to fit and supply them.
Your child's squint can be treated in a number of ways and often more than one treatment or a combination of treatments may be needed to get the best result for your child's vision. How your child's squint is treated will depend on the type of squint they have. Most treatment for squints is on-going and it usually involves regular visits and examinations at the hospital for a number of years.
Some of the most common ways that squint can be treated include:
- Occlusion therapy (patching)
It’s important for your child to have properly prescribed glasses to give them clear vision in both eyes. Usually the first step is for your child to be tested to see if they need glasses. Most children with a squint may be prescribed with a pair of glasses that they will need to wear all the time. It can be difficult to get children to wear glasses and if your child isn't keen to wear their glasses, a lot of encouragement will help. It’s not unusual for your child to say that they can see better without them at first. This is because they have been working their eyes so hard to focus without glasses that they find it difficult for their eye to “relax” into the glasses and let the glasses do the focusing for them. This usually settles once your child is wearing their glasses all the time.
You may notice when your child wears their glasses that their squint becomes less noticeable or disappears completely. This type of squint is known as an accommodative squint. When your child takes their glasses off you will notice that their squint can be seen again. This is because the glasses need to be worn to correct the squint. Many children may only need to wear glasses to treat their squint.
Occlusion therapy (Patching)
Occlusion therapy is used to improve the vision in a lazy eye. You may be asked to cover your child's good eye with a patch. Your child then uses their weaker eye to see and it helps to make this eye work harder. If your child wears glasses, patching should always take place when glasses are worn. Some children with a slightly lazy eye do not need patching as the weaker eye may improve with glasses correction alone. Your orthoptist will let you know how often, for how long and when will be the best time for your child to wear their patch. This may be during school hours so it can be important to explain to your child's teacher how and when the patch should be worn.
Sometimes when patching is successful and has been stopped there is a chance that your child's sight may get a little worse. Because of this risk they may still need to be carefully monitored by their orthoptist or optometrist even though they don't need to wear their patch anymore.
It is possible to use eye drops as an alternative to a patch. Atropine drops will blur vision in your child's good eye enough so that the child will start to use the other eye, just like when wearing a patch. Using drops like this doesn't work for all children and you would need to discuss this option with your orthoptist or ophthalmologist to see if it is possible.
In some cases exercises can be useful to strengthen the ability of the eyes to work together. This type of treatment is usually helpful in older children and is commonly used together with glasses and/or surgery.
A number of children may 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.
Squint surgery is usually performed under general anaesthetic which means your child will be asleep (unconscious) and unable to feel any pain. Normally the operation is a day case procedure. This means your child may not have to stay in hospital overnight.
The operation usually weakens or strengthens the muscles of the eye so that the eyes are better aligned. Surgery will not improve the vision in a lazy eye and for most children, glasses may still need to be worn after the surgery.
There are different reasons why squint surgery may be carried out. The surgery may help the eyes develop and work together and to stop a lazy eye from developing or it may be used to make the eyes look straighter (but not work together as a pair). It’s not uncommon for more than one operation to be necessary. This does not mean that something has gone wrong but that fine-tuning may be needed to obtain the best results.
There is no age limit on surgery, it may be performed on children under the age of 1 and also on those aged 16 and over. However, in older children and adults, the operation will not help with the eyes working together as a pair but may be more for cosmetic reasons.
Botulinum Toxin Injection (Botox)
Some children may be offered treatment with a botox injection. This injection weakens the muscles that pull the eyes towards each other and in children is carried out under general anaesthetic. It is only considered for certain types of squint, it can be carried out together with squint surgery or on its own. The effect is temporary but may be effective for some squints.
The outcomes for children with squint
It can be reassuring to know that the treatments for squint and the amblyopia it may cause are generally very effective if the squint is detected and treated early. In these cases, most children will have good vision in each eye in the long-term.
If a squint or amblyopia is not picked up before the age of 7 or 8 then it can have a permanent effect on the vision in one eye. The level of vision in this eye will vary between individuals and some may retain a reasonable level of sight. Most people who have had a squint or lazy eye since childhood that wasn’t successfully treated are totally adapted to their vision and it doesn’t cause them any problems day to day.
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. 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 and both eyes working together. Keeping this in mind can help you and your child plan their career choice for the future. You can ask your orthoptist for more information about certain jobs and whether your child may be affected by this.
Sometimes adults who have had squint surgery as a child may need to have further surgery later in life to straighten the eyes again.
Currently there is no treatment to correct amblyopia in adulthood.
It’s completely natural to be worried when your child is diagnosed with a squint, particularly if you haven’t noticed any problems with their eyes. It can be reassuring to know that prompt diagnosis and assessment of a squint usually means that it can be dealt with so that it doesn’t cause long term changes to vision.
Most children with squints have a good level of vision and both eyes working together once they have had treatment.
Children whose treatment isn’t as successful may have poor sight in one eye. This may not cause them any problems throughout their life as many people adjust very well to poor vision in one eye only. However it’s important that someone with good vision in only one eye should have regular eye examinations with an optometrist to make sure that the eye they rely on is healthy. An optometrist will be able to give you advice on how often your child should have their eyes tested.
As far as we are aware there is no support group for children and families affected by squint.
There is an organisation for people with sight in one eye which may be useful for people with amblyopia (lazy eye), although most people will not experience any day to day problems if they have had poor sight in one eye since childhood.
Tel: 0845 108 3161 (local call cost)
The British and Irish Orthoptic Society (BIOS) provides information for lay or professional persons including information leaflets in download format.
British and Irish Orthoptic Society
Tavistock House North
Tel: 0207 387 7992
This information was written in collaboration with BIOS.
105 Judd Street
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