Strabismus & Amblyopia
Understanding the Problem
The first thing to remember is that the turn doesn't worry your child very much. They are not in any pain or discomfort and as far as they are concerned they can't see what all the fuss is about. This is because when the eye is turned the brain does not pay any attention to it so your child isn't seeing double.
Sometimes when a turn is first developing the child will get intermittent times of double vision but the brain learns very quickly to turn one of the pictures off. This is called suppression and if it occurs long enough then the eye that's being turned off won't function as well in terms of eyesight.
When the eyesight becomes poor this is called a "lazy eye" (amblyopia) and this will have to be treated before we can get the brain to pay attention to that eye. Lazy eyes are quite common in young children. About 5% of children need treatment for a lazy eye.
It's important for you understand that your child's eye turn is not your fault. It's nothing you did to your child that made their eye turn
So Your Child Has A Turned Eye
It is perfectly natural as a parent to feel anxious and a little upset by the fact that your child has a turned eye. One of your concerns will be that your child doesn't look nice with a turned eye.
You may have noticed that your child doesn't perform certain visual and eye-hand tasks as well as expected because of the eye turn.
You may also be getting lots of so called "helpful" advice from your friends and relatives as to what you should be doing about the turned eye
Why Did This Happen?
There are a number of reasons why an eye may turn. As a result the treatment for each varies. The most common reasons are:
A very small percentage of children develop an eye turn very soon after birth (in the first 3 to 6 months). Usually this type of turn is an inward eye turn. The cause of this turn is a problem with the way the eye muscles are controlled by the brain. Usually these cases require an operation in order to straighten the eye.
Most children develop a turned eye after age 12 months. The majority of these are the result of longsightedness. Simply stated, the child has a focus problem, which causes the secondary eye alignment problem that you can see. When your child focuses on an object, in order to see it clearly, there needs to be stimulation of the muscles around the eye, to pull the eyes in. Eventually the brain learns to adapt to this by leaving one eye in constantly and “turning it off”. This eye turn is more likely to be noticed as the child becomes more involved in close work (ages 2 to 4 years). This is because close work requires a greater focus effort to keep things clear hence the greater pull inwards of the eyes. The turn may also be precipitated by illness or fatigue again due to the fact that there is an increased effort involved in keeping the world clear under these situations. There can also be a genetic predisposition for this to occur. This type of eye turn is treated with spectacles.
Some individuals seem to have an excessive stimulation of the inner muscles that pull the eyes inwards when the eyes try to focus. This can occur even with relatively low degrees of long-sightedness. Eventually the brain learns to leave one eye in and “turns it off” to alleviate the effort of coping with the misalignment.
Some children have a combination of the two latter conditions above. Either way it is important that you understand that rarely is an eye turn due primarily to a muscle problem.
This is when the eyes point in two different directions. One eye may look straight ahead while the other can be turned in, out, up, or down. This can casue double vision, but the brain tries to fix this by ignoring the image from the eye that is not looking straight. This can keep that eye from developing properly.
This is reduced vision in one eye compared to the other. Less commonly there are forms of amblyopia that involve both eyes. Amblyopia is the most common cause of visual impairment among children. Recent research has shown that amblyopia is a disorder of the brain’s ability to use both eyes together as a team.
Amblyopia is an active process due to suppression, or the brain actively ignoring the information coming from one eye. In addition to poor visual acuity, people with amblyopia are more prone to have difficulties with depth perception, eye movements related to reading, and visual decision making while driving.
There are a number of options for treating your child's turned eye.
No single approach is better than the others. The approach depends on what type of eye turn your child has. We may need to use two or even all three to get the best result.
Eyeglasses or contact lenses (proper lenses can help reduce stress so that the under-used eye can start to work more efficiently)
Patching or penalization of the better-seeing eye
Binocular vision activities
A program of vision therapy may help improve the visual abilities of the eye with amblyopia including accommodation (focusing), fixation, saccades, pursuits (eye tracking) and spatial skills (eye-hand coordination). A program of vision therapy may also reduce the frequency of patching since the goal of amblyopia therapy is to improve eye coordination, improve stereopsis (depth perception) and reduce suppression.
Hess RF, et al. Binocular vision in amblyopia: structure, suppression and plasticity. Ophthalmic Physiol Opt. 2014 Mar;34(2):146-62
S Grant, MJ Moseley. Research review of eye-hand coordination, walking, driving, and reading skills of children and adults with amblyopia. Strabismus, 2011; 19(3) 119-129
Mansouri B, et al. Binocular training reduces amblyopic visual acuity impairment. Strabismus. 2014 Mar;22(1):1-6