Squint (Strabismus) in Children

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A child with a squint may stop using the affected eye to see with. This can lead to visual loss called amblyopia, which can become permanent unless treated early in childhood. This treatment usually involves patching the good eye, to force the use of the affected eye. Sometimes surgery is needed to correct the appearance of a squint.


This leaflet only deals with childhood squints.

The movement of each eye is controlled by six muscles that pull the eye in specific directions. The lateral rectus muscle pulls the eye outwards. The medial rectus muscle pulls the eye inwards. The superior rectus muscle is mainly responsible for upwards movements, whilst the inferior rectus muscle mostly pulls the eye downwards. Finally, the superior and inferior oblique muscles help to stabilise the eye movements - particularly for looking downwards and inwards, or for upward and outward movements.




Yes, squints can be divided into different categories:

  • By the direction of the squinting (turning) eye:
    • An eye that turns inwards is called an esotropia.
    • An eye that turns outwards is called an exotropia.
    • An eye that turns upwards is called a hypertropia.
    • An eye that turns downwards is called a hypotropia.
  • By the cause:

About 5 in 100 children aged 5 years have a squint. It is quite common to notice a brief squint in children when they are tired or daydreaming. Babies sometimes cross their eyes - it is quite normal for this to happen occasionally, especially when they are tired.

Some squints are much more obvious than others. You might notice your child has an eye that does not look straight ahead. Another sign of squint is that your child might close one eye when looking at you, or turn his or her head on one side.

Congenital squints of unknown cause

Congenital squint means that the child is born with a squint, or it develops within the first six months of life. In most cases, the eye muscles are not balanced but the reason for this is not known.


Squint related to refractive errors

Refractive errors include: short sight (myopia), long sight (hypermetropia) and astigmatism. This leads to problems with focusing. These are all conditions that are due to poor focusing of light through the lens in the eye. An astigmatism is a vision problem where the surface of the eye (the cornea) or the lens, is more oval-shaped, rather than round. When the child with a refractive error tries to focus to see clearly, an eye may turn. This type of squint tends to develop in children who are 2 years or older, in particular in children with long sight. The squint is most commonly inward looking (an esotropia).

Other causes

Most children with a squint have one of the above types of squint and are otherwise healthy. However, in some cases, a squint is one feature of a more generalised genetic or brain condition. Squints can occur in some children with cerebral palsy, Noonan's syndrome, Down's syndrome, hydrocephalus, brain injury or tumour, a rare type of eye cancer (called retinoblastoma) and several other conditions.


Amblyopia is sometimes called a 'lazy' eye. It is a condition where the vision in an eye is poor and it is caused by lack of use of the eye in early childhood. The visual loss from amblyopia cannot be corrected by wearing glasses. However, it is usually treatable (see below).

If amblyopia is not treated before the age of about 7-8 years, the visual impairment usually remains permanent.


If, for any reason, a young child cannot use one or both eyes normally then vision is not learnt properly. This results in impaired vision (poor visual acuity) called amblyopia. The amblyopia develops in addition to whatever else is affecting the eye. In effect, amblyopia is a problem with the development of vision in the brain, rather than a problem within the eye itself. Even if the other eye problem is treated, the visual impairment from amblyopia usually remains permanent unless it is treated early enough.

A squint is the most common cause of amblyopia. In many cases of squint, one eye remains the one that sees (the dominant focusing eye). The other, turned eye (the squinting one) is not used to focusing and the brain ignores the signals from this eye. The turned eye then fails to develop the normal visual pathways in childhood and amblyopia develops in this eye. See separate leaflet called Amblyopia for more details.

How the squint looks

A squint can be a cosmetic problem. Many older children and adults who did not have their squint treated as a child have reduced self-esteem because of the way their squint looks to other people.

Impaired binocular vision



It is important to diagnose a squint (and amblyopia) as early as possible. Routine checks to detect eye problems in babies and children are usually done at the newborn examination and at the 6- to 8-week review. There is also a routine preschool or school-entry vision check.

Some newborn babies have a mild intermittent squint that soon goes, reducing by 2 months of age and gone by 4 months of age. However, fixed squints are usually permanent unless treated. So, as a guide:

  • A squint seen in a newborn baby is likely to resolve if it is intermittent (comes and goes), reducing by 2 months of age and gone by 4 months of age.

Any baby or child with a suspected squint is usually referred to an orthoptist. An orthoptist is a health professional who is specially trained to assess and manage children with squint and 'lazy' eye (amblyopia). If necessary, an orthoptist will refer a child to an eye surgeon (ophthalmologist) for further assessment and treatment.

Various tests can be done to check a child's vision. Sight tests can even be done for babies. Tests to find a squint can involve covering and uncovering each eye in turn. This often shows which eye has the squint and how it moves. The pupils of the eye can be checked with a torch, to check they become smaller (constrict) with light and widen (dilate) when the light is removed. An ophthalmoscope is a special torch used to examine the back of the eye (the retina). Very occasionally, if another cause of squint is suspected (other than a congenital squint or one related to refractive errors), a scan of the eye or the brain may be needed.

Treatment typically involves the following:

  • Treating amblyopia (visual loss) if this is present.
  • Surgery is often needed to correct the appearance of the squint itself and may help to restore binocular vision in some cases.

Treating 'lazy' eye (amblyopia)







Correcting refractive errors





Botulinum toxin


For 'lazy' eye (amblyopia), if it develops


For improving the appearance of the eyes



Original Author:
Dr Tim Kenny
Current Version:
Peer Reviewer:
Dr Colin Tidy
Document ID:
4335 (v42)
Last Checked:
Next Review:
The Information Standard - certified member
Now read about Strabismus (Squint)

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