A squint, also known as strabismus, is a condition where eyes are misaligned because of an incorrect balance of the muscles that control them. One eye can turn inwards (Esotropia), outwards (Exotropia) or upwards (Hyper or Hypotropia), while the other eye looks forward.
Squints can be constant or intermittent (only apparent at certain times, for example when tired).
The cause, severity and direction of a squint varies from person to person. It's usually spotted in childhood, sometimes within weeks of a baby being born, and affects 5-8% of children (one or two in every 30).
How does a squint affect vision?
This depends on the type of squint and the age of your child. In a young child a squint can lead to the development of a lazy eye. To avoid double vision, the brain ignores the signals from the eye with a squint, and only ‘sees’ images from the normal eye. As the squinting eye is not being used, it will eventually become ‘lazy’.
In an older child, a squint may give double vision but not produce a lazy eye. This is because their vision will be fully developed. Occasionally, children may experience headaches or blurred vision while their squint is being controlled.
If the vision in the squinting eye is poor, a child may have to wear a patch over the other eye to encourage the vision to develop.
Can adults develop a squint?
Squints that have been corrected as a child can sometimes reappear in adulthood. It's unusual to develop a squint as an adult, but if you do it may result in double vision because, having been trained to collect images from both eyes, the adult brain is much less able to suppress the image from the weaker eye. If a new squint develops in an adult, you always need a thorough investigation to find the cause.