What is Lazy Eye?

A Guide to Amblyopia

Treating lazy eye
Treating lazy eye. National Eye Institute, National Institutes of Health

Lazy eye, or amblyopia, is an eye problem that sometimes occurs in growing children. In a child with lazy eye, the right and left eyes have different qualities of vision. One eye may produce weak or distorted images compared to the other eye. Over time, the brain learns to ignore the images sent by the weaker eye and only accept images from the stronger eye. In other words, the weak eye never learns to "see."

Lazy eye is often associated with crossed eyes, and usually develops before the age of 6. It is estimated that three percent of children under six have some form of amblyopia.

What causes lazy eye?

Any interference with clear vision in either eye during the critical period (birth to 6 years of age) can result in amblyopia. The most common causes of amblyopia are strabismus, problems related to nearsightedness or farsightedness, and structural problems.
  • Strabismus (crossed eyes): Children with crossed eyes often have double vision when they use both eyes at the same time. A child may try to correct this by focusing with one eye more than the other.
  • Problems related to severe nearsightedness or farsightedness: When a child is nearsighted or farsighted, the problem may affect each eye in a different way. For instance, one eye may have normal vision, but the other is blurred. The brain will eventually choose to ignore the images sent from the eye with the poorer vision.
  • Structural problems: A growing child's vision is sometimes blocked by a structural problem of the eye or eyelid such as a congenital cataract, a drooping eyelid, or a scar on the cornea.

Symptoms of lazy eye

Lazy eye usually causes no symptoms. A child may often favor one eye or have a tendency to bump into objects on one side.
Parents sometimes suspect a problem because their child looks cross-eyed, squints or tilts his or her head in awkward ways. Lazy eye is usually detected during vision screenings, before or after starting school. A screening exam will show better vision out of one of the eyes.

Diagnosis of lazy eye

An eye doctor can detect lazy eye during a comprehensive eye exam. Early diagnosis increases the chance for a complete recovery. This is one reason why the American Optometric Association recommends that children have a comprehensive optometric examination by the age of 6 months and again at age 3. Lazy eye will not go away on its own. If not diagnosed until the pre-teen, teen or adult years, treatment takes longer and is often less effective.

Treatment of lazy eye

Treating lazy eye has two goals: to produce clear vision in both eyes and to strengthen the weaker eye. The most common treatment is to patch the child's stronger eye for a certain amount of time each day, forcing the weaker eye to work harder.
Treating lazy eye may also include a combination of prescription lenses, prisms, and vision therapy.

Lazy eye and strabismus are not the same condition

Many people mistakenly believe that a person who has a crossed or turned eye (strabismus) has a "lazy eye," but amblyopia and strabismus are not the same condition. This confusion may be caused by the fact that strabismus can cause amblyopia. Amblyopia without a large degree of eye turning (strabismus) usually cannot be noticed by a parent or by a pediatrician. Only an eye doctor can detect this type of amblyopia during a comprehensive eye examination. This is why early infant and pre-school eye examinations are so important.

Things to watch for

If you notice any of the following symptoms, make an appointment with an eye doctor for your child to have a comprehensive eye examination:
  • Eyes that appear to be crossed
  • Holding the head in awkward positions while looking at distant objects
  • Frequent squinting
  • Constantly closing or covering one eye

What you need to know about lazy eye

If lazy eye is not detected and treated early in life, loss of vision and depth perception can occur. However, it is possible to improve lazy eye at any age with proper treatment. Infants and pre-school children need comprehensive vision screenings. An eye exam by a pediatrician or a school nurse is usually not adequate for the detection of amblyopia.

Source: American Optometric Association. Lazy Eye. 10 Jul 2007.

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