107

Strabismus is a disorder in which both eyes do not line up in the same direction. Therefore, they do not look at the same object at the same time. The most common form of strabismus is known as “crossed eyes.” The oculomotor muscles around each eye allow for both eyes to focus on the same object. When someone has strabismus, these muscles do not work together which causes the eyes to look in different directions. When this occurs, two different images are sent to the brain—one from each eye. This confuses the brain. In children, the brain may learn to ignore or suppress the image from the weaker eye. If the strabismus is not treated by training or surgery, the eye that the brain ignores will never see well and the brain will rely solely on the image from the stronger eye. This loss of vision in one eye is called amblyopia. In most children with strabismus, the cause is unknown and the problem is present at or shortly after birth.

Amblyopia, also called lazy eye, is a type of poor vision that happens in just one eye. It can result from strabismus or anisometropia. Amblyopia develops when there’s a breakdown in how the brain and the eye work together, and the brain can’t recognize the sight from one eye. Normally, the brain uses nerve signals from both eyes to see. But if an eye condition makes vision in one eye worse, the brain may try to work around it. It starts to “turn off” signals from the weaker eye and rely solely on signals from the stronger eye. This creates monocular visions instead of binocular. Amblyopia starts in childhood, and it’s the most common cause of vision loss in kids. However, early treatment works well and usually prevents long-term vision problems. If caught and treated early, stereo vision can develop normally (Fig.10.8.1).