Squint and Paedriatic
What is Squint?
Technically know as Strabismus, Squint is a condition where the two eyes are misaligned.
That is both eyes do not appear to be looking in the same direction. One eye may
be looking at an object and the other eye may be turned in or out or up or down.
A squint may be constant (always apparent) or intermittent (seen only at times -
usually when tired). Squints are more commonly seen in children. The condition affects
2% of children under 3 years and 3% of children and young adults.
It may be seen always in one eye or it may alternate and appear to shift from one
eye to the other. For example the Right eye which is straight to start with, turns
in as the Left eye looks straight or visa versa.
Types of Squint:
- Squints are classified depending on direction of the squinting eye
- Convergent squint or esotropia when one eye is turning in
- Divergent squint or exotropia when the eye is turning out
- Vertical squint (Hypertropia / Hypotropia) when one eye is pointing upwards/downward
The precise cause of squint is unclear in a large proportion of childhood squints.
It is understood that the condition may be due to mis-functioning of the brain in
moving the eye muscles synchronously. There is no defect in the eye muscles themselves.
The other causes leading to a squint can be refractive errors like hypermetropia
(long-sightedness), myopia (short-sightedness), astigmatism or unequal refractive
error in both eyes.
Brain trauma and certain brain tumours may also cause the eye to turn in. If a child
develops a sudden in-turning of the eye associated with nystagmus (involuntary eye
movements), an urgent assessment is required as it suggests a build up of intracranial
pressure or a possible tumour.
Abnormality of the eye muscles or in their nerve supply as in:
EARLY DIAGNOSIS: If the proper visual impulses are not transmitted to the
brain in the first few months after birth, which is the critical period of visual
development, amblyopia will develop and there will be loss of 3D (binocular) vision.
Non surgical treatment:
Prisms: These are specialised glasses used to treat double vision of sudden
onset. They can be used as a temporary measure and are later incorporated into the
usual spectacles. They can also improve the appearance of a squint in some patients
where surgery is not an option.
Non surgical treatment: These are specialised glasses used to treat double
vision of sudden onset. They can be used as a temporary measure and are later incorporated
into the usual spectacles. They can also improve the appearance of a squint in some
patients where surgery is not an option.
Treatment done by Prisms
BOTOX: In adults and occasionally in children, Botulinium toxin may be the
first line of treatment. The toxin is injected into the muscle at the surface of
the eye. It temporarily paralyses the muscle in the direction of the squint and
balances the forces producing the misalignment. It causes an overcorrection initially
and the eye may move in the direction opposite to the squint in the first few weeks.
The eye will gradually straighten and then return to its original position. Repeat
injections are usually required to maintain the corrected position of the eye.
To achieve surgical correction, the eye muscles in one or both eyes (depending on
the degree and direction of the squint), are tightened or loosened. The muscles
are shortened and reattached to the eye to tighten or moved further back which has
the effect of loosening. If the eye is turning in (convergent squint), the muscle
which pulls the eye in (the medial rectus) is moved back and the outer muscle (the
lateral rectus) is tightened to straighten the eye. The amount of surgery is based
on normograms that are tables which have been developed based on results of muscle
surgery in thousands of patients.