What is squint (strabismus)?
This is a condition of abnormal deviation of alignment of one eye
in relation to the other. It is normal for newborn babies to have eyes that cross or wander sometimes, especially when they are tired. However, if the child's eyes cross or one eye wanders to the side after 3 months of age, even if it happens only once in a while then a consultation with a doctor is necessary. Also, if the child often looks with one eye closed, or with his head turned to one side, it is necessary to inform the doctor.
Why is strabismus a problem?
Normal vision needs both eyes to look in the same direction at the same time. When a child has a crossed or wandering eye, he gets a different picture from each eye. The child's brain blocks out the picture from the weaker eye. If this eye is not fixed when a child is young, the child's brain will always ignore the pictures from the weak eye. This kind of vision loss is called amblyopia. This is the most serious problem caused by crossed or wandering eyes.
What are the causes and risks?
Strabismus is caused by a lack of coordination between the eyes, causing the eyes to point in different directions. The eyes do not focus simultaneously on a single point.
Most cases of strabismus in children are of unknown cause. More than half are present at or shortly after birth (congenital strabismus). Strabismus in children is frequently associated with amblyopia, or lazy eye. Children with esotropia, or eyes turning in, are often farsighted. Strabismus in children may also occur in cerebral palsy, or in children who have diminished vision from any other cause.
Acquired strabismus in adults may result from injuries to the orbit or brain, including closed head injuries and strokes. Persons with diabetes often have loss of circulation to muscle which turns the eye outward, causing an acquired paralytic strabismus. Loss of vision in one eye from any cause will usually cause the eye to gradually turn outward (exotropia).
A family history of the disease is a risk factor. Farsightedness may be a contributing factor. Any other disease causing visual loss may result in strabismus as a complication.
What are the symptoms?
- Eyes that appear crossed
- Eyes that do not align in the same direction
- Uncoordinated eye movements
- Double vision
- Vision in only one eye with loss of depth perception
How is it diagnosed?
The doctor will first determine if the child truly has strabismus. The wide fold of skin next to the bridge of the nose in children may give the false appearance of esotropia. If the child has strabismus, a workup will be done to determine the cause of the strabismus.
The physical examination will include a detailed examination of the eyes. The patient may be asked to look through a series of prisms to determine the extent of eye divergence. The eye muscles will be tested to determine the strength of the extraocular muscles.
- Standard ophthalmic examination
- Visual acuity
- Retinal examination
- Neurological examination
What is the treatment?
Initially, strategies to strengthen the weakened muscles and thereby realign the eyes are attempted. Glasses may be prescribed. Eye muscle exercises may be prescribed. If amblyopia is present, patching of the preferred eye may be done to force the child to use the amblyopic eye.
Some children need an operation to straighten their eyes. The operation is usually not done until the weak eye has got stronger by being used more. The surgery is fairly simple, but it does not always make the eyes exactly straight. Sometimes it has to be done again later on.
How long does the treatment last?
Since the most important part of treating strabismus is to make the weak eye to work harder, it is very important that one follows the directions for eye patching or eye drops that is suggested by the doctor. Usually the treatment goes on for many months, or even a few years. Sometimes less patching (or fewer eye drops) will be needed as time goes by. This treatment usually helps make the weak eye as strong as the good eye.
When the child is about 7 or 8 years old, the vision in the weak eye will be as good as it can get with treatment. The earlier the treatment starts, the easier it is to fix the problem.
What is the prognosis?
With an early diagnosis, the defect can usually be corrected. With delayed treatment, vision loss in one eye may be permanent.