When one eye develops good vision while the other does not, the eye with the poorer vision is called amblyopic. Usually, only one eye is affected by amblyopia, but it is possible for both eyes to be "lazy." This condition is called bilateral amblyopia.

The condition is common; approximately two or three out of every 100 people has amblyopia. The best time to correct amblyopia is during infancy or early childhood.

Kids at poolAmblyopia in children and adults

Newborn infants are able to see, but as they use their eyes during the first months of life, their vision improves. During early childhood years, their visual system changes quickly and their sight continues to develop.

In order to have normal vision, it is important that both eyes develop equal vision. If a child has amblyopia and cannot use his or her eyes normally, vision does not develop properly and may even decrease. After the first nine years of life, the visual system is normally fully developed and usually cannot be changed.

If amblyopia treatment is not begun as early as possible, several problems can develop that can seriously affect vision from childhood into adulthood:

  • the amblyopic eye may develop a serious and permanent visual defect;
  • depth perception (seeing in three dimensions) may be lost, because good vision in both eyes is needed;
  • if the stronger eye becomes diseased or injured, it can mean a lifetime of poor vision.

People with amblyopia in one eye are more than twice as likely to lose vision in the healthy eye from trauma. If the vision in one eye should be lost later in life from an accident or illness, it is essential that the other eye have normal vision.

Another important reason to make sure amblyopia is detected and treated as early as possible in childhood: people who have good vision in only one eye may find they are limited in the kinds of jobs they can perform.

Your ophthalmologist can teach you how amblyopia can be treated, and can help you and your child successfully carry out this treatment.

What is refractive (or anisometropic) amblyopia?

Refraction is when the eye focuses light onto the retina to form a visual image. A refractive error occurs when the light is not properly focused in the eye and vision is blurry. When a child has refractive, or anisometropic, amblyopia, it means he or she has a different amount of refractive error in each eye. When this is the case, the brain will use the better-seeing eye and essentially "turn off" vision from the weaker eye. At first, eyeglasses may help by correcting the refractive error in both eyes, allowing them to work equally together. Then the amblyopia may be further treated to help improve vision and depth perception.

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Reviewed by Dr. Denise Satterfield on Sept. 1, 2013

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