What is Strabismus?
Strabismus or eye turn, is when the eyes are not aligned or pointing at the same thing.
How does Strabismus affect how you see?
The brain does not like this because it sees two objects occupying the same point in space… so it learns very quickly to turn off the image coming from the turned eye. The eye still sees but the brain does not pay attention to what the eye is looking at! This is called suppression and if it occurs long enough then the eye that’s being turned off won’t develop normal eyesight (it develops Amblyopia or lazy eye), eye movement skills and/or eye processing (perception) abilities.
Signs and symptoms of a child developing an eye turn?
The first thing to understand is that the eye turn does not worry the child. They are not in any pain or discomfort, they can see clearly (out of the straight eye) and as far as they are concerned they don’t have a problem and can’t see what all the fuss is about!
Usually an acquired eye turn starts to occur after the first 6 months of a child’s life. The turn might only be noticed at first when the child is tied or upset. A child rarely “grows out of it” and invariably a little intermittent eye turn will develop into a constant larger eye turn (Esotropia) by the time the child is 3 to 4 years old.
If the eye turn is an outwards turn (Divergent Exotropia) the child may also close one eye in bright sunlight.
Why did my child develop an eye turn?
- Congenital Strabismus: Only a very small percentage of children are actually born with an eye turn. Some develop an eye turn very soon after birth (in the first 2 to 4 months). The actual underlying cause is not fully understood. Surgery is usually required for this type of eye turn in the first 12-24 months of life.
- Acquired Strabismus: About 7% of children between the ages of 6 and 17 years develop an eye turn. Of these 47% have a family history of an eye turns.
These turns can develop due to a:
- Significant refractive error in one or both eyes: A large degree of long-sightedness in one or both eyes can cause an inward eye turn. Whenever we drive our focusing system it stimulates the eyes to converge (turn in). Normally we can control this convergence and maintain normal eye alignment except when very tired or if we have a large amount of long-sightedness to also overcome. Often this type of turn is first noticed when the child is becoming more involved in prolonged close work around the age of 2 to 4 years.
- High accommodative convergence ratio: Some individuals have an excessive stimulation to converge the eyes whenever the eyes try to focus up close. This is called a high Accommodative Convergence Ratio. Even with relatively low degrees of long sightedness or little near work demand the eyes get excessive stimulation to converge. Eventually the brain learns to leave one eye in and turn it off to alleviate the stress and demand of trying to keep the eyes turned out.
Treatment of Strabismus
Spectacles to train the eyes straight?
Spectacles (or contact lenses) can compensate for the long sightedness and reduce the stimulation to converge the eyes.
In 80% of cases spectacle lenses combined with visual therapy will achieve a functional cure.
Spectacles must be worn constantly to achieve this and may need to be in a bifocal or multifocal design to achieve the fastest results.
Visual Therapy for Strabismus?
Visual training isn’t just about doing exercises on eye muscles. The eye muscles are not the problem in an acquired eye turn.
Visual training is about teaching the brain how to straighten the eyes and developing the mechanism by which it can maintain the eyes straight.
Depending on how long the eyes have been turned it can take 6 to 18 months before normal stable binocular vision is fully established.
Surgery for Acquired Strabismus?
In most cases it is not a matter of operating on an eye muscle to pull the eye straight. This may well give a cosmetic improvement but fails to address the underlying cause of the acquired eye turn and hence can fail to develop normal binocular vision. (i.e. Functional Cure.)
Surgery is most successful in treating congenital turns, turns due to muscle palsy and in cases where therapy has not produced a good cosmetic outcome.
The earlier an eye turn is detected and treated the better the chances are of achieving a full functional cure.