A squint, or strabismus, is a condition in which the eyes do not align properly. One eye turns inwards, upwards, downwards, or outwards, while the other one focuses at one spot.
It can happen all the time or intermittently.
This usually occurs because the muscles that control the movement of the eye and the eyelid, the extraocular muscles, are not working together.
As a result, both eyes are unable to look at the same spot at the same time.
It can also happen because a disorder in the brain means that the eyes cannot correctly coordinate.
Strabismus also makes binocular vision impossible, so it is harder for the person to appreciate depth perception.
It is estimated to affect around 4 percent of the population in the United States.
Types of strabismus
There are several different types of strabismus, including a lazy eye.
There are different types of strabismus. They can be described by the cause or by the way the eye turns.
The following terms describe strabismus by the positions of the eye:
Hypertropia is when the eye turns upwards
Hypotropia is when the eye turns downwards
Esotropia is when the eye turns inwards
Exotropia is when the eye turns outwards
An early diagnosis of strabismus will enable more effective treatment. In the past, it was thought that after a “critical period”, strabismus could not be treated.
While treatment up to the age of 6 years is believed to be most effective, strabismus can be treated at any time.
Strabismus can lead to double vision if it returns in adulthood.
Untreated, it can lead to amblyopia, or “lazy eye,” in which the brain starts ignoring input from one of the eyes.
The brain ignores one of the eyes to avoid double vision.
If there is poor vision in the affected eye, a child may benefit from wearing a patch over the other eye to encourage the vision to develop.
Sometimes a squint that was treated successfully in childhood returns later in adulthood.
This may lead to double vision in the adult because, by that time, the brain has been trained to gather data from both eyes, so it cannot ignore one of them.