Eye Movement Disorders
Strabismus
Most of us are fortunate because our eyes started to work as a team very early in infancy and have continued to work together ever since. We are able to focus each eye on whatever we look at, regardless of the direction, and our brain combines the picture or image from each eye into the mental picture we actually see in three dimensions.
About two percent of every 100 children are not as fortunate. For a variety of reasons, their eyes do not work as a team. Both eyes are not directed or focused at the same object. This condition is called "strabismus."
The child with strabismus rarely complains. In most cases, it is the appearance of the eye that first catches the parent's attention. A child should be examined by an ophthalmologist whenever the eyes appear not to be working together.
There are three basic kinds of strabismus: esotropia, exotropia and hypertropia, depending on which direction the eyes are deviated.
Amblyopia
Amblyopia (lazy eye) is another frequent condition, occurring in about three or four of every 100 children. When a child is born with normal eyes, he or she has the potential for good vision in both eyes, but must learn to see with each of them. If for some reason, the child prefers to use one eye more than the other, the preferred eye learns to see well but the other suffers from lack of use. It does not learn to see as well, even with glasses. The non-preferred eye is said to be lazy or have amblyopia.
One of the common causes for lazy eye is strabismus. When the child's eyes are pointed in different directions, the child has to use one eye at a time to avoid seeing double. If he or she uses one eye more than the other, the other eye becomes lazy.
Children without strabismus can also develop a lazy eye. Even though their eyes are straight, one eye is preferred more than the other. This non-preferred eye becomes lazy and does not learn to see.
Amblyopia does not bother the child because there are no symptoms. It is found only by checking the vision in each eye. This can be done fairly accurately in any child three years or older. For this reason, all children should have their vision tested by age four.
The treatment for amblyopia involves forcing the lazy eye to be used more often. Usually this is accomplished by patching the preferred, or good eye. This may have to be continued for several months until each eye sees equally well. Fortunately, it is usually successful in restoring good sight. Sometimes the patching must be continued intermittently until age nine. If the lazy eye is out of focus, eyeglasses may be required, in addition to patching the good eye, to obtain the best sight.
Eye Movement in Children
Many children enter the world with less than 100 percent of their expected visual capacity, a deficiency that is not always obvious to parents or medical professionals. One sign of possible eye problems, however, is eye movement. Eye movements tell a lot about vision, even if a child is pre-verbal. How well a child follows faces or large objects is a clue to his or her visual abilities. Another indication of a possible disorder is unusual jiggling of a child's eye(s), called nystagmus. These eye movements can be constant or intermittent. They can be horizontal, vertical, oblique, torsional (circular) or combinations of the above. Thus, the study of eye movement can provide important information regarding sight.
Nystagmus
Nystagmus is a condition where the eyes make repetitive movements. The eyes can jerk exclusively in one direction, or make back and forth movements. With nystagmus, the eye can look jittery and can affect both eyes or just one eye.
For additional information on nystagmus, you may obtain printed copies of "Idiopathic Infantile Nystagmus: Diagnosis and Treatment," (J AAPOS 1997;1:67-82) and "Nystagmus: Questions and Answers" (J Ophthalmic Nursing & Technology 1998;17(5):183-87) by contacting the Foerderer Center for the Study of Eye Movement Disorders in Children at (215) 928-3003.
