An Overview of Amblyopia, or Lazy Eye

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Amblyopia, or lazy eye, is a condition in which one eye is weaker than the other. Because of an abnormal development of vision in infancy or childhood, vision is decreased in one or both eyes. Amblyopia is the leading cause of vision loss in children.

During vision development, some of the nerve pathways between the brain and the eye aren't stimulated properly, teaching the brain to see only blurry images with the affected eye. This causes the brain to favor one eye, due to poor visual ability in the other eye. Amblyopia is typically treated in young children, upon detection. With prompt, proper treatment, vision can usually be improved.

Symptoms

Symptoms of amblyopia are not always obvious. Most children with amblyopia do not complain about vision difficulties because they do not realize something is wrong. The following symptoms may indicate a possible problem:

  • Decreased vision in one or both eyes
  • Misaligned eyes (one eye turned inward)
  • Head tilting
  • Squinting
  • Poor depth perception       

With amblyopia, vision may be good in one eye and reduced in the other. A child may adapt and tend to use the better eye while ignoring the weaker eye. Therefore, the weaker eye is not used and becomes "lazy."

However, sometimes a parent or teacher might notice certain symptoms of a vision problem. The child may appear to have crossed eyes or may tend to squint when trying to focus. The child may also tilt his head in order to see objects more clearly. Some kids may also show signs of poor depth perception, making it difficult for them to judge distances.

Vision screenings are strongly recommended in young children, as vision problems can be detected early enough for successful treatment. Pediatricians perform regular vision checks on newborns and young children in order to identify problems that may be fixed in order to prevent amblyopia from developing. Sometimes a pediatrician will recommend a complete eye examination by an optometrist or ophthalmologist.

Causes

Ablyopia develops when one eye has much better focus than the other. Vision begins to develop shortly after birth. During vision development, vision centers in the brain are formed. If for any reason an infant is unable to use her eyes correctly, the vision centers may not develop properly and vision may be decreased.

Several things can interfere with normal brain–eye connections such as a major difference in the focusing power of each eye. Large differences between the two eyes in farsightedness, for example, can lead to the development of amblyopia. The brain chooses to use the eye with the clearest image and ignores the other eye. This neglect causes the vision in the other eye to worsen.

Misalignment of the eyes can also cause amblyopia. If the eyes are crossed, for example, the brain will tend to favor the most aligned eye, causing the worse aligned eye to become weaker.

When the eyes are misaligned, the child may have double vision. In order to not see double, the brain chooses to ignore one of the images. This is called suppression. Also, amblyopia can develop if something causes vision to be blocked or blurry. For example, a cataract (cloudy lens) or scarring caused by an injury might lead the brain to favor the clearer eye, leading to decreased vision in the blurry eye.

Milestones in Infant Vision Development

Diagnosis

The earlier amblyopia is diagnosed, the better the chances are to avoid permanent vision loss. Sometimes, a child will have no obvious signs of a vision problem. Early detection and treatment of amblyopia are important for normal vision development.

The American Academy of Ophthalmology suggests that children should have their vision tested by a professional before their 4th birthday. Infants should be checked by an ophthalmologist if there is a family history of childhood cataracts, misaligned eyes, or other vision problems.

An ophthalmologist checks a baby's or young child's vision by covering one of the eyes and watching how well they can follow a moving object. The doctor may also cover one of the child's eyes and watch how the child reacts. If the child tries to look above or below the patch, attempts to pull it off, or begins to cry, the covered eye may have amblyopia.

For proper diagnosis, the ophthalmologist will conduct a complete medical eye exam on the child. Other eye problems may be detected that could be affecting their vision.

What to Expect at a Baby's Eye Exam

Treatment

Treatment usually consists of covering the good eye and forcing the child to use the weaker eye. Forcing the brain to use the weaker eye makes it stronger.

Treatment should be started as soon as possible, preferably under the age of 6. Early treatment while the child is young will help improve developing connections between the brain and the eye.

Treatment will be based on the cause of the amblyopia and options may include the following:

Patching

This is the most common treatment for amblyopia. Patching the good eye forces the brain to start using the weaker eye. If the patch is worn for a few hours every day, the weaker eye will eventually become stronger. This will force the brain to use the image from the lazy eye, eventually making the weaker eye stronger. Vision improvement could take a few months to several years, depending on the severity of amblyopia and the diligence of patching the eye.

Glasses

Glasses are used when amblyopia is caused by severe refractive errors. Glasses will allow the brain to use the eyes together and eventually develop normal vision. Glasses must be worn all day, except during bathing, swimming, or sleeping.

Eye drops

Sometimes, a doctor may prescribe eye drops that blur vision instead of patching the good eye. Atropine eye drops blur the child's vision in the good eye, forcing the brain to use the weaker eye.

Surgery

Eye muscle surgery is sometimes an option if other treatments fail to improve vision. Surgery is often performed if the amblyopia is caused by a cataract. This type of surgery involves loosening or tightening the eye muscles.

A Word From Verywell

It is very important to treat amblyopia at a young age. If amblyopia is detected early and promptly treated, a child has a good chance of regaining normal vision. However, treating an older child for amblyopia is much more difficult. Follow your doctor's treatment advice carefully for the best outcome.

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Article Sources
  • Boyd, Kierstan. "Amblyopia: What Is Lazy Eye?" EyeSmart, American Academy of Ophthalmology (AAO) 1 Sept 2017.