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Amblyopia in children: Overview

Last Update: September 24, 2014; Next update: 2017.

Introduction

Normally, the brain processes the information coming in from both eyes equally. This is needed for the best possible vision.

In some children, however, one eye is favored by the brain because it provides a better image. If this happens, the other eye is neglected from childhood on, and it does not get the chance to fully develop. This is known as amblyopia or "lazy eye." Amblyopia, the medical term for lazy eye, is taken from ancient Greek and means "dull vision."

Symptoms

If your child has a wandering eye or you think he or she may have an eye problem, it is important to have it checked out by an eye doctor. Difficulties recognizing objects might be a sign of amblyopia too. For example, if your child has to hold toys or other objects very close to their eyes or tilts their head to one side to see them better.

Causes

Amblyopia develops when the brain keeps receiving different information from both eyes and cannot form a single image. The most common cause is strabismus (also referred to as a "squint" or "crossed eyes"). If a child has strabismus, one eye will look straight ahead while the other looks up, down or to the side.

If the eyes send two different images to the brain, the brain cannot combine these images to form one single view, resulting in double vision. The brain may start ignoring the images sent by the weaker eye to improve overall vision.

Most children who have strabismus have amblyopia: Somewhere around 60 to 70% of children with strabismus are affected by it. Only about 2% of children who do not have strabismus have amblyopia.

Another common cause of amblyopia is refractive errors (focusing problems). There are 3 different kinds of refractive error:

  • Near-sightedness (or short-sightedness): where the eye can only focus clearly on objects that are close
  • Far-sightedness: where the eye can only focus clearly on objects that are far away
  • Astigmatism: Everything the affected eye sees looks blurry because the lens or the cornea is deformed.

Refractive errors are more likely to cause amblyopia when they affect each eye differently. One eye might not be affected while the other one is, or one eye could be far-sighted while the other one is near-sighted, for example.

Some eye conditions may cause amblyopia in rare cases – such as cataracts, a droopy eyelid (called ptosis) or an eye without a lens (aphakia).

Prevalence

Amblyopia is a common eye problem in childhood. In Germany, it is estimated that about 4 to 6% of children are affected. It usually does not develop after the age of 7 or 8.

Diagnosis

There are several tests that can be used to diagnose amblyopia in children:

  • The doctor can use eye charts to see how good your child’s vision is. The exact kind of test will depend on several factors, including your child’s age. There are special tests for babies and toddlers.
  • A test can also be done to see whether your child’s eyes are aligned properly. A slight squint is not always visible to the naked eye.
  • A physical check-up can be done to see whether the poor eyesight is caused by something else, like a cataract.
  • The exact refractive power of your child’s eyes can be determined using a special instrument called a retinoscope. This involves shining light into the eye and seeing how the light reflects off the retina at the back of the eye. By holding different corrective lenses in front of the light, it is possible to determine exactly how well the eye can focus.
  • Once the refractive power has been determined, a further eye test can be done using an eye chart. This time the child wears glasses that correct any focusing problems he or she may have.

These tests are generally safe. Eye drops are often used before a retinoscopy examination to dilate (open) the pupils and they can sometimes cause a burning sensation in the eyes or skin irritation.

Screening

Experts agree that most of our vision develops by age five. They recommend that amblyopia be detected and treated as early as possible to prevent both life-long impaired vision as well as problems in social development.

Based on these recommendations, an additional screening test specially designed to detect amblyopia was introduced in Germany in 2008 for all preschool children with statutory insurance. In Germany, screening programs for children have names made up of "U" and a number related to the order in which they are given. U7a is the name of this test: it is intended for children about to turn three (between the ages of 24 and 36 months).

Treatment

Wearing glasses is not an immediate fix for amblyopia. But there are different ways to help the affected eye catch up with its partner, or at least help make sure that the problem does not get worse over time. Treatment might only be needed for a few weeks, but sometimes it needs to continue for quite a long time to get the best results.

Sources

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