A squint is a condition where one eye is out of alignment, i.e. one eye looks straight ahead whilst the other points in, outwards, up or down. If the eye that normally turns is forced to look straight ahead (e.g. by covering the straight eye), then the other eye will turn. Squints may be constant (obvious all the time) or intermittent (only seen from time to time). Most squints develop before 3 years of age, but sometimes they develop later.

Squints can affect the eyesight in childhood, as the brain will begin to ignore a squinting eye causing the sight in it to be worse that in the other eye. This is what most people mean by a ‘lazy eye’ (Amblyopia).

In older children and adults, a new squint, or one that is getting worse may cause double vision (Diplopia) or, less frequently, headaches and ‘eye strain’.