What is Strabismus?
Strabismus (eye turn) is a visual problem where the eyes are not aligned properly causing the eyes to point in different directions.
Understanding the condition
The first thing to understand is that the eye turn does not worry your 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 can’t see what all the fuss is about. This is because when one eye is not looking at the same thing that the other eye is looking at the brain learns to turn it off so as not to see two of everything. This is called suppression and if it occurs long enough then the eye that’s being turned off won’t develop normal eyesight, eye movement skills and eye processing (perception) abilities.
Why did my child develop an eye turn?
Genetic Factors: About 7% of children between the ages of 6 and 17 years have an eye turn. Of these 47% have a family history of an eye turns.
Types of eye turn
- 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 mths of life.
1. 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.
2. Due to a 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.
Training the eye
Spectacles to train the eyes straight:
- Spectacles (or contact lenses) 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 training isn’t just about doing exercises on eye muscles.
- Visual training is also 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.
- 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 turn and hence will 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.
- Surgery is generally not successful at achieving a functional cure for Acquired eye turns.