What is amblyopia?

Amblyopia is reduced vision that occurs when an eye does not develop normal sight during early childhood. It is also called a lazy eye.

How does it occur?

Normally, a newborn baby's vision is blurred. It improves as the baby gets older and uses her eyes. Both eyes work together (called binocular vision) and send images to the brain. The brain blends the two images into a single, clear picture. If for some reason the images are different, or if one image is blurry, the brain ignores the image from one eye to avoid confusion. This may mean that normal vision does not develop in the eye that the brain ignores. After some time, this condition may become permanent.

The images from the eyes may be different because of:

• Strabismus (also called crossed eyes). If your brain were to try to use the pictures coming from 2 eyes that are not aligned the same way, you would see double. To make sense of the confusing images, the brain ignores the image coming from one eye.
• Vision disorders. One eye may be more nearsighted, farsighted, or astigmatic than the other eye. These 3 vision problems keep the eye from focusing correctly. The brain uses the image from the eye that sees better. The other eye may stop developing.
• Diseases. Childhood cataracts and eyelid problems that prevent the eye from opening all the way can keep a young child's eyes from developing normally.

If this problem is detected and treated when the child is young, both eyes may develop normal vision and work together. After the age of 8 years, the visual system is usually fully developed. Treatment of children younger than 6 years is more effective than treatment of older children. However, even older children may benefit from treatment. Treatment should begin as soon as the condition is detected.

What are the symptoms?

Babies often do not show any symptoms of amblyopia. However, they may have trouble following an object with their eyes or may have crossed eyes. Toddlers may favor one eye. They may become fussy when one eye is covered but not the other. Older children may complain of eye pain, watery eyes, or headaches. If you suspect that there is anything abnormal about your child's eyes at any age, see a doctor. Most of the time, amblyopia is detected during a vision exam at school or by a pediatrician.

How is it diagnosed?

A pediatrician, primary care doctor, or preschool staff member may suggest that a child needs a complete eye exam. An eye doctor can diagnose amblyopia by watching how a baby or child follows objects with his eyes or by watching his movements when one eye is covered.

How is it treated?

Treatment in children usually begins by patching the eye that has better vision. Patching forces the brain to use the "lazy" eye. Some doctors prescribe eyedrops to blur the "good" eye instead of putting a patch on it. The eye doctor also treats the problem that led to the amblyopia. Glasses can help correct nearsightedness, farsightedness, or astigmatism. Crossed eyes may require eye muscle surgery, glasses, or both.

If amblyopia is detected early and treated properly, a child can develop normal binocular vision. If treatment does not take place early, glasses may provide good vision. However, the lazy eye may never see as well as the stronger eye and the eyes may not work together.

Most people can work and play well with one lazy eye. For example, Babe Ruth had amblyopia. However, airline pilots and interstate truck drivers, for example, are required by law to have good vision in both eyes.