What Is a Squint?
A squint, or strabismus, is the name given to a condition in which both eyes do not point in the same direction. Whilst one eye looks straight ahead, the other eye turns to point inwards, outwards, upwards or downwards. The movements of each eyeball depend upon the action of six muscles, four of which are straight and two slanting. Defects in these may produce a squint.
Long-sightedness in children often produces an inward squint, especially if the child is looking at something close at hand. Short-sightedness may produce an outward squint. Paralysis is the usual cause of a squint which appears after the years of childhood. This is caused by some disease affecting the brain or the nerves of the eye muscles.
If one eye has better vision than the other the good eye may be used much more than the other, which may begin to function less and less well. Treatment for squinting must begin as early as possible with the wearing of glasses, which may have one dark lens over the good eye to stop it being used.
This prevents the bad eye from becoming worse. Special exercises, called orthoptic exercises, which help to strengthen the eye muscles, are given and, in some cases, an operation is necessary to strengthen a weak eye-muscle or to weaken an over-strong one.
Squints are common and affect about 1 in 20 children. You might even spot that your baby has a squint. Most squints develop before preschool age, usually by the time a child is 3 years old. Sometimes squints develop in older children, or in adults.
Squints can be divided into different categories:
.By the direction of the squinting (turning) eye:
.An eye that turns inwards is called an esotropia.
.An eye that turns outwards is called an exotropia.
.An eye that turns upwards is called a hypertropia.
.An eye that turns downwards is called a hypotropia.
.Whether the squint is present all the time (constant), or comes and goes (intermittent).
.Whether the affected eye turns when the eyes are open and being used (manifest squint) or whether the eye turns only when it is covered or shut (latent squint) but looks fine when the eyes are open.
.Whether the severity (angle) of the squint is the same in all directions or not:
.A concomitant squint means that the angle (degree) of the squint is always the same in every direction that you look. That is, the two eyes move well, all the muscles are working but the two eyes are always out of alignment by the same amount, no matter which way you look.
.An incomitant squint means that the angle of squint can vary. For example, when you look to the left, there may be no squint and the eyes are aligned. However, when you look to the right, one eye may not move as far and the eyes are then not aligned.
.By age of onset. Most squints develop at some time in the first three years of life. Some develop in older children and adults. Squints that develop in children usually have different causes to those that develop in adults.
.By the cause:
.In many cases of childhood squint, the reason why a squint develops is not known.
.In some cases of childhood squint (and most cases of adult squint), the squint occurs because of a disorder of the eye, the eye muscles, the brain or the nerves.