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.  This vulnerable period of visual development ends around age eight or nine.

One common cause 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. The 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 temporarily blurring the preferred, or good, eye. This can be accomplished with patching or drops.  This treatment may have to be continued for several months until each eye sees equally well. Fortunately when caught at an early age, 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 require, in addition to patching the good eye to obtain the best sight.