A squint (strabismus) is a condition where the eyes point in different directions.
Squints are common and affect around one in 20 children. They usually develop before five years of age, but can appear later.
Signs and symptoms of a squint
One of your child's eyes may turn inwards, outwards, upwards or downwards, while the other eye looks forward. Squints may not be constant, and a minor squint isn't always obvious.
A squint can cause blurred or double vision, but children may not realise there's a problem.
Left untreated, lazy eye (amblyopia) can develop. This is when the brain starts to ignore signals coming from the eye with the squint.
When to see a doctor
It's quite normal for the eyes of newborn babies to "cross" occasionally, particularly when they're tired. However, speak to your GP if you notice this happening to your child after three months of age.
If your child looks at you with one eye closed or with their head turned to one side, it may mean they're experiencing double vision and could be a sign they have a squint. If this happens repeatedly, take your child to see your GP as soon as possible.
They may refer you to a specialist called an orthoptist, for tests. Many squints are detected during routine eye checks carried out at certain stages in your child's development.
Why do squints happen?
The exact cause of a squint isn't always known. Some babies are born with a squint (congenital squint) and some develop it later (acquired squint).
Acquired squints are often caused by the eye attempting to overcome a vision problem – known as refractive errors. Types of refractive errors include:
short-sightedness (myopia) – the ability to see distant objects is reduced
long-sightedness (hyperopia) – the ability to see close-up objects is reduced
astigmatism – where the cornea at the front of the eye is unevenly curved, which causes blurred vision
In rare cases, a squint may be the result of:
childhood illnesses – such as measles
some genetic conditions – such as Down's syndrome or cerebral palsy
hydrocephalus – caused by a build-up of fluid in the brain
other eye problems affecting the muscles or the retina (the layer of light-sensitive nerve cells at the back of the eye)
A child's risk of having a squint is increased if there's a family history of eye problems, if they're born prematurely or with a low birth weight.
How are squints treated?
To be most successful and avoid long-term problems, most squints should be treated as soon as possible. Treatment is most effective in very young children.
Several types of treatment are available for squints, including:
Glasses – worn constantly to correct vision problems (refractive errors). Children are usually given plastic lenses instead of glass.
Eye exercises – in some cases, special eye exercises may help the eyes to work together.
Botulinum toxin injections into one of the eye muscles – the injection weakens the muscle, allowing the eyes to realign for around three months. The eyes may stay in position or may need further treatment. Children will usually be given a sedative before the injection.
Botulinum toxin injections can cause temporary side effects, such as:
a droopy eyelid (ptosis)
the eye "drifting" slightly, so it appears as if one eye is looking up
some bleeding over the white part of the eye
If your child has a lazy eye, they may need to wear a patch over their "good" eye to encourage the eye with the squint to work harder (occlusion).
If other treatments aren't successful, surgery will probably be required. This involves moving the muscles that control the movement of the eye to improve their alignment and help the eyes work together.
Risks from surgery are rare, although sometimes more than one operation will be needed.
Recovering from surgery
It can take several weeks to fully recover from corrective squint surgery.
The eye may feel painful or itchy for a short time afterwards, and you may have temporary double vision.
Diagnosing a squint
Squints are often detected in children during routine eye checks.
These are usually carried out:
at birth or by the time your baby is 14 days old
at around six to eight weeks of age
before your child starts primary school or during their first year
However, if any of these checks don't happen or if you're concerned about your child's vision, speak to your GP. After an initial assessment, you may be referred to an eye specialist.
Three types of eyecare professionals may be involved in caring for a squint:
optometrists – who carry out sight tests, prescribe glasses, and can also detect eye conditions
orthoptists – who arespecially trained to assess problems relating to eye movements and how the eyes work together
ophthalmologists – whospecialise in eye conditions, their treatments and carry out any necessary surgery
Different tests can be used to help diagnose a squint and assess the level of vision. These will vary according to your age, but may include:
looking at a light
matching letters and pictures
reading a letter chart
looking at visual targets at different distances, first with one eye covered and then the other
Other tests may also be needed to determine whether glasses are needed.
The retina and the optic nerve will also be examined to make sure there are no other problems.
In most cases, eye drops will be used to widen the pupils before the eyes are examined. This makes it easier for the ophthalmologist to study the back of the eyes.
Sight tests are free for children under 16 years of age. Find opticians in your local area.
Having surgery for a squint
If other treatments are unsuccessful, surgery may be needed to correct a squint.
Surgery can be used to:
improve the alignment of the eyes (and therefore their appearance)
help the eyes work together
Surgery involves moving the muscles attached to the outside of the eye to a new position. It may be necessary to operate on both eyes to balance them, even if the squint is only in one eye.
The operation is carried out under general anaesthetic and usually takes less than an hour to perform. It's often carried out as a day case, so your child can go home the same day.
You may be able to accompany your child to the operating theatre and stay with them until they've been given the anaesthetic. A nurse will be with your child throughout the procedure.
During the operation, your child's eye will be kept open using an instrument called a lid speculum. The ophthalmologist (eyecare specialist) will detach one part of the muscle connected to your child's eye and will either move it backwards to weaken the pulling effect, or shorten it to increase the pulling effect. Once the correction has been made, the muscles will be sewn back into place using dissolvable stitches.
Risks of surgery
As with any kind of operation, there's a risk of problems after surgery to fix a squint. Ask your ophthalmologist to discuss any possible risks of surgery with you before the operation.
Risks of eye surgery include:
further surgery being needed – which is sometimes needed if the squint is severe
the eye remaining red for a long time after the operation – this is rare, but may be caused by scar tissue forming on the surface of the eye
double vision may occur after the operation – this usually resolves itself after a week or so
the squint may recur, or the operation may need to be repeated for another reason
in rare cases, the inside of the eye can be damaged during surgery
an infection may develop after the operation – this is possible with any type of surgery
One study that looked at squint surgery for adults estimated that around one in five people may need more than one operation to treat their squint successfully. Double vision occurred in less than one in 100 cases. This usually either improves with time, or it can be treated with further surgery, for example.
In children, it's more common to need another operation to correct the squint, particularly if the first operation was carried out when the child was very young. Some studies have found that around six out of 10 children who have squint surgery at about one year of age need to have another operation at some point.
Other complications in children are usually rare, but you should ask your ophthalmologist for more information.
Recovering from surgery
It can take several weeks to fully recover from corrective eye surgery. After surgery, the eye is likely to be sore for a few days. The pain can be treated using simple painkillers, such as paracetamol. Children under 16 years of age shouldn't be given aspirin. If the pain doesn't improve, speak to your eyecare specialist or visit your GP.
Following eye surgery, a pad may be put over the affected eye, which is usually removed before being discharged from hospital. There is no need to wear a patch or bandage at home and you can return to daily activities, such as reading, as soon as you feel able to. The aim is to get the eyes working normally as quickly as possible.
Your care team can give you more specific advice about returning home after an eye operation, but some general tips include:
drink water at regular intervals
the stitches can take up to six weeks to dissolve and it may feel like there's a bit of grit in the eye, or the eye may be itchy – try not to rub it
avoid washing your hair for a few days and try not to get any soap or shampoo in the eye
your child shouldn't play in sand or use face paint for two weeks after the operation
regular follow-up visits with an eyecare specialist will be required
if glasses were needed before the operation, they will probably still need to be worn
Returning to school or work
Your child should be able to return to school or nursery about a week after surgery. If you've had surgery, you should also be able to return to work after about a week.
After surgery, avoid playing sports for around two weeks. You may need to avoid contact sports, such as rugby, for up to a month. Swimming should be avoided for at least a month after the operation.
If you've had surgery to correct a squint and you drive, ask your surgeon when you can drive again. You shouldn't drive if you have double vision.