Congenital squints
The cause of a squint is not always known. Squints sometimes run in families and a baby can be born with the condition. This is called a congenital squint.
Squints are also sometimes the result of childhood illnesses, or other sight-related problems, such as refractive errors.
Refractive errors
Squints are sometimes caused by the eye’s inability to focus the light that passes through the lens. This is known as a refractive error. Types of refractive errors include:
- short-sightedness (myopia) - a sight problem that affects your ability to see distant objects
- long-sightedness (hyperopia) - a sight problem that affects your ability to see close-up objects
- astigmatism - where the cornea at the front of the eye is unevenly curved, which causes blurred vision
If a child has a refractive error, their eye may turn inwards as it attempts to focus. Squints that are caused by refractive errors usually develop in children who are two years of age or over. They tend to be most common in children who are long-sighted.
Other causes
Although most squints are congenital (inherited from a family member) or caused by refractive errors, they can occasionally be the result of:
- childhood illnesses, for example viral infections such as measles
- some genetic conditions, such as Noonan syndrome
- a brain condition, such as hydrocephalus, where there is a build-up of fluid in the brain
- eye problems, such as abnormal development of the muscles that move the eye, or a problem with the retina (the layer of light-sensitive nerve cells at the back of the eye)
Risk factors
Some factors that may increase the risk of a child having a squint include:
- having a family history of squints or lazy eye (amblyopia)
- having a condition that affects the nervous system, such as cerebral palsy
- being born early (prematurely) or with a low birth weight
