Strabismus involves deviation of the alignment of one eye in relation to the other. This is sometimes called Crossed Eyes, Esotropia, Exotropia, Squint, or Walleye. Caused by a lack of coordination between the eyes, the eyes look in different directions and do not focus together on a single point. In most cases of strabismus in children, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth (congenital strabismus).
In children, when the two eyes fail to focus on the same image, the brain may learn to ignore the input from one eye. If this is allowed to continue, the eye that the brain ignores will never see well. This loss of vision is called Amblyopia and it is frequently associated with strabismus.