Each eye has seven muscles, six on the outside of the eyeball and one on the inside. The outside muscles move the eye. The inside muscle keeps things clear. Occasionally, Strabismus is caused by a "damaged" outside eye muscle. Usually, however, an eye deviates because the BRAIN fails to coordinate the twelve out-side-of-the-eyeball muscles to correctly position the two eyes.
The reason for this lack of coordination is, as yet, unknown. Sometimes the condition runs in families. Sometimes a child has many other developmental problems such as poor speech or deficient eye-hand and eye-body coordination and the strabismus seems to be another symptom of this general coordination problem.
The Cosmetic Problem
Strabismus causes a cosmetic problem. Children on the playground make fun of the child whose eyes look different. Adults with strabismus can have difficulty during social situations as others struggle to figure out at which eye to look. This cosmetic disfigurement caused by strabismus is the main reason that brings such patients into the doctor's office. Consider the following success story for instance:
Before vision therapy my left eye was stuck over . . . [near my nose] and because of that I was very embarrassed and had low self-esteem. My right eye was very tired and both eyes were red all the time. Since therapy both eyes are straight and clear. I am no longer embarrassed and am happy to interact with other people because I don't have to worry about what my eye is doing or what they are thinking about my eye.
The Seeing Problem
Strabismus affects more than the way we look. It also affects the way we see. When eyes are straight, each eye sends a picture to the brain. The brain combines these two pictures into a three dimensional image, thus creating "depth perception."
When an eye first crosses, the pictures from the two eyes no longer match and the world doubles and runs together. At this point, the person with a turned eye may run into things, knock over drinking glasses, etc. In time though, if the eye is allowed to continue crossing, the child usually learns to ignore or "suppress" the information from the deviated eye. As a result, the child no longer suffers from double vision. At the same time, however, depth perception is lost. And, if the same eye is always turned in, the eye can become so ignored that it goes partially blind. This partial blindness is called "amblyopia."
Treatment of Strabismus
Studies show that children typically do not "outgrow" strabismus. To avoid loss of sight in the turned eye, or loss of depth perception, active treatment is therefore necessary. The most common treatments follow.
If the strabismus is unilateral (meaning that the same eye always turns in) the "good" eye may be patched to make the "bad" eye work and avoid blindness. While such patching preserves sight, it does little to develop depth perception.
As mentioned above, inside each eyeball there is a single muscle used to keep things clear. If our eyes are normal, when we look far away we relax these insidel muscles to see clearly. When we look up close we flex these inside eye muscles to see clearly.
When a person is far-sighted (sees better far away than up close) the inside muscles have to flex when the person looks far away and have to flex even more when the person looks closer. As these muscles flex they tell the brain: "We're working hard so we must be looking up close." In response, the brain automatically crosses the eyes. Wearing glasses to correct for the farsightedness may allow the eyes to straighten.
In these cases in which glasses are needed to align the eyes, the good news is that oftentimes between the ages of nine and sixteen, children become less farsighted. As a result, the glasses are no longer needed to keep the eyes straight. When the child is younger, however, these glasses (or contact lenses) must be worn. Of those children whose eye's appear straight when first wearing glasses, about half will need additional treatments to keep their eyes from deviating again in the future.
Eye-muscle-surgery is used to alter the outside eye muscles to compensate for the difficulty with eye-brain coordination. For a number of patients, such surgery may be a necessary part of treatment. The surgery itself, however, is frequently cosmetic in nature. It makes the eyes look straight but may not lead to the information from the two eyes being blended properly in the brain. Without this blending, there is nothing to maintain the eyes in proper alignment and additional surgeries may be needed.
Optometric Vision Therapy
Vision therapy works by teaching the brain to blend the information from the two eyes. Frequently this process can align eyes without surgery. Once the eyes are aligned, the other six "Visual Abilities" are also worked to ensure the straight eyes work with the rest of the body to maximize performance during school, sports, and work.
If you or your child has an "intermittent" eye turn (the eyes are turned part of the time and straight part of the time) vision therapy can align the eyes in more than eight out of ten cases. In other words the success rate is greater than 80%. If the eyes are always turned, the doctor will have to look at a number of other factors to determine what the chances are to align the eyes non-surgically.
More importantly, when aligned eyes and depth perception are combined with the other visual abilities, the patient will both "look" better and "see" better, and the eyes will stay straight once the treatment is completed. Consider this success story written by a young lady who had already received cosmetic eye-muscle surgery as a child:
"I began therapy in January of my senior year in highschool. Before than I had always struggled in school. I was not a bad student, but there was plenty of room left for improvement. Today is my last day of Vision Therapy, and of highschool, and thanks to the therapy I've made all A's and one B this quarter and exempted 4 out of 5 exams. When I was little, I used to read anything I could get my hands on, but when I had reading and studying to do for school I quickly quit my reading for fun. Now I am able to do both because my eyes don't quit on me. My hand-eye coordination and my sports have also improved. More than anything, I've noticed that my right eye no longer turns in. People used to be able to tell when I was tired because my eye would always become lazy and turn in, but not anymore!"