Amblyopia (lazy eye) is the decrease of vision in one or both eyes due to abnormal vision development during childhood. The vision process involves both the eyes and the brain. Amblyopia is the failure of the vision-sensing portions of the brain to develop normally, which results in blurry vision. It is one of the leading causes of vision loss in children.

Amblyopia is generally the result of poor early visual development. It usually occurs before the age of 8. Infants born prematurely or with low birth weight are at a greater risk for developing the condition.

An estimated 2 to 4 percent of children have amblyopia. The chance of amblyopia developing during adulthood is very small.

Amblyopia usually results from a failure to use both eyes together. It can be caused by the presence of crossed eyes (strabismus), unequal farsightedness or nearsightedness (refractive error), or a physical obstruction of vision like cataracts.

If there is a large enough difference in the degree of nearsightedness, farsightedness or astigmatism between the two eyes, or if the eyes are crossed, the brain learns to ignore one eye in favor of the other.

Normally, the images each eye sends to the brain are identical. When they differ too much, the brain learns to ignore the poor image sent by one eye and "sees" only with the good eye.

LThe vision of the eye that is ignored becomes weaker from lack of use.

The amblyopic eye is not blind in the sense that it is entirely without sight.

Amblyopia affects only the central vision of the affected eye. Peripheral (side) awareness will remain the same.

Amblyopia usually has few symptoms. People with amblyopia may also have crossed eyes or a large difference in the refractive error between their two eyes. A child with amblyopia may noticeably favor one eye and have a tendency to bump into objects on one side.

A comprehensive eye examination can determine the presence of amblyopia. The earlier it is diagnosed, the greater the chance for a successful treatment.

When amblyopia occurs only in one eye, the good eye takes over and the individual is generally unaware of the condition. That is why it is important to have your child's vision examined at about six months, at age three and again before he or she enters school.

Corrective lenses, contact lenses, prisms, occluders and vision therapy are often used to treat amblyopia.

Corrective lenses, contact lenses, prisms, occluders and vision therapy are often used to treat amblyopia.

Vision in the amblyopic eye may continue to decrease if left untreated. The brain simply pays less and less attention to the images sent by the amblyopic eye. Eventually, the condition stabilizes, and the eye is virtually unused. It is very difficult to effectively treat amblyopia at this point.

Early detection and treatment of amblyopia and significantly unequal refractive errors can reduce the chances of one eye becoming amblyopic.

Amblyopia can limit the occupational and leisure activities you can do. Activities requiring good depth perception may be difficult or impossible to perform. In addition, if your good eye becomes injured or develops vision problems, you may have difficulty maintaining your normal activities.