Amblyopia

What is amblyopia?

Amblyopia is reduced vision that occurs when an eye does not develop normal sight during early childhood. It is also called 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, the brain ignores the image from one eye to avoid double vision. This may mean that normal vision does not develop in that eye.

The images from the eyes may be different because of:

• Strabismus, or "crossed eyes". If your brain were to try to use the pictures coming from two eyes that were not aligned the same way, you would see a jumble of images. 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 three vision problems keep the eye from focusing correctly. The brain uses the image from the stronger eye. 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 age 10 the visual system is usually fully developed. Treatment in children younger than 6 years old is more effective than in older children. 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 react strongly to having one eye 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.

In an older person, amblyopia is often suspected when no prescription of eyeglasses can correct reduced vision.

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.

If an adult's vision cannot be corrected to 20/20 with glasses and if a thorough exam reveals no other cause for impaired vision, he or she probably has amblyopia.

How is it treated?

Treatment in children usually begins by patching the stronger eye. 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. Strabismus may require eye muscle surgery, glasses, or both.

Unfortunately, there is no treatment for amblyopia in adults.

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 vision in the lazy eye may never be as good as that in the stronger eye.

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.