A squint is a condition where one eye turns inwards, outwards, upwards or downwards while the other eye looks forwards. The misalignment of the eye is caused by an incorrect balance of the eye muscles. The medical name is strabismus.
Squints are common and affect about one in 20 children. They usually develop during the first three years of life, but can appear later. A squint is often spotted in early childhood, sometimes within weeks of a baby being born.
Types of squint
There are four different types of squint. They are classified according to the direction in which the eye turns.
- Esotropia: the eye turns inwards.
- Exotropia: the eye turns outwards.
- Hypertropia: the eye turns upwards.
- Hypotropia: the eye turns downwards.
Hypertropia and hypotropia are less common than esotropia and exotropia.
Squints can also be:
- constant, apparent at all times, or
- intermittent, only apparent at certain times.
The cause, severity and direction of a squint vary from person to person.
How does a squint affect vision?
It is very important that a squint is picked up and treated as early as possible to avoid vision problems developing. If a squint is identified when a child is young, there is a good chance it will be successfully treated.
In young children, a squint can mean binocular vision fails to develop (see the box, left). This may result in a ‘lazy eye’ (amblyopia). To avoid double vision, the child’s brain ignores the signals from the eye with the squint and only recognises images from the normal eye. As the squinting eye is not being used, it eventually becomes ‘lazy’.
In older children, a squint may cause double vision but not result in a lazy eye. This is because their vision has fully developed and their brain is unable to ignore signals from the eye with the squint.
If the vision in a child’s squinting eye is poor, they may have to wear a patch over their other eye to encourage the vision in the squinting eye to develop.
Can adults develop a squint?
Occasionally, squints that have been corrected during childhood reappear in adulthood. Squints that affect adults may cause double vision as the brain has been trained to collect images from both eyes.
If you develop a new squint, visit your GP as soon as possible. They may refer you to an ophthalmologist (an eye care specialist) who will carry out an examination to identify the cause.
Squints may cause a cosmetic problem in adults whose squint was not treated when they were young. In such cases, the appearance of a squint my lead to low self esteem.
