Squint (strabismus)

Squint (also known as strabismus) is a condition that arises because of an incorrect balance of the muscles that move the eye, faulty nerve signals to the eye muscles and focusing faults (usually long sight). If these are out of balance, the eye may turn in (converge), turn out (diverge) or sometimes turn up or down, preventing the eyes from working properly together.

Squint can occur at any age. A baby can be born with a squint or develop one soon after birth. Around five to eight per cent of children are affected by a squint or a squint-related condition, which means one or two in every group of 30 children.

If you notice your child appears to have a squint after they are six weeks old, you should have their eyes tested by an optometrist as soon as possible. Many children with squints have poor vision in the affected eye. If treatment is needed, the sooner it is started the better the results.

The video below should be viewed in conjunction with the text beneath it and preferably watched while your optometrist discusses it with you.

Get Adobe Flash player

  • Normally, the two eyes point in the same direction.
  • A “squint” or “strabismus” occurs when the two eyes are misaligned.
  • This can happen in either eye and the misalignment can be in any direction.
  • A squint may occur for a number of reasons.
  • Sometimes, one or more of the muscles that move the eyes is in the wrong place.
  • Sometimes the muscles do not work as they should.
  • A longstanding squint does not usually affect vision
  • … although the squinting eye may be “lazy”.
  • A recent squint can result in double vision and should be fully investigated.

Types of squint

There are several types of squint. The causes of squint are not always known, but some children are more likely to develop it than others. Among the possible causes are:

Congenital squint
Sometimes a baby is born with a squint, although it may not be obvious for a few weeks. In about half of such cases, there is a family history of squint or the need for glasses. The eye muscles are usually at fault. If squint is suspected, it is important that the baby be referred for accurate assessment at the earliest opportunity. Sometimes a baby has what is known as ‘pseudo squint’ which is related to the shape of the face, but a baby with a true squint will not grow out of it.

Long-sight (hypermetropia)
Long-sightedness can sometimes lead to a squint developing as the eyes ‘over-focus’ in order to see clearly. In an attempt to avoid double vision, the brain may automatically respond by ‘switching off’ the image from one eye and turning the eye to avoid using it. If left untreated, a ‘lazy eye’ (amblyopia) may result. The most common age for this type of squint to start is between 10 months and two years, but it can occur up to the age of five years. It is usually first noticed when a baby is looking at a toy, or at a later age when a child is concentrating on close work, such as a jigsaw or reading.

Childhood illnesses
Squint may develop following an illness such as measles or chickenpox. This may mean that a tendency to squint has been present but, prior to the illness, the child was able to keep his or her eye straight.

Nerve damage
In some cases a difficult delivery of a baby or illness damaging a nerve can lead to a squint.

How can I tell if my child has a squint?

People often think that they can tell if a child has a squint if the eyes look unusual or the two eyes look different. This is not necessarily a squint. Symptoms of squint are often difficult to detect, especially in younger children. Older children may complain of eyesight problems such as double vision. If it is suspected that a child has a squint, your health visitor, child health clinic, GP or school doctor/nurse should be asked about a referral to an optometrist, ophthalmologist or hospital eye clinic for assessment.

Isn’t a squint just a cosmetic problem?

Certainly the appearance can lead to problems for the child, but a squint is not merely a cosmetic problem. If left untreated, it can lead to a permanent visual defect in the squinting eye. Treating squint would be cosmetically desirable and glasses or surgery can give good results in many cases.

What can be done about squint?

Treating squint varies accordingly to the type of squint. An operation is not always needed. The main forms of treatment are:

  • Glasses – to correct any sight problems, especially long-sight.
  • Occlusion – patching the good eye to encourage the weaker eye to be used. This is usually done under the supervision of an orthoptist.
  • Eye drops – certain types of squint can be treated with the use of special eye drops.
  • Surgery – this is used with congenital squints, together with other forms of treatment in older children, if needed. Surgery can be performed as early as a few months of age.