Amblyopia

What Is Amblyopia?

Amblyopia (am-blee-OH-pee-uh) — or "lazy eye" — is a condition in which the eye and brain don't work together as they should. Kids who have it will develop good vision in one eye and poor vision in the other.

Kids often get used to this vision problem, and might not mention it to parents. As a result, their amblyopia might not be diagnosed for months or even years, while parents chalk up poor grades or clumsiness to a child not being academically or athletically gifted.

But sometimes the solution is as easy as visiting the eye doctor. Treatment for amblyopia can correct the way the eye and brain work together and strengthen vision. Early treatment is important — waiting or not getting a proper diagnosis could lead to permanent vision loss later.

What Happens in Amblyopia?

From birth until about age 8, a child's eyes and brain form vital connections. Anything that blocks or blurs vision in one or both eyes can slow down or prevent these connections.

If that happens, the brain might not fully recognize the images seen by one or both eyes. Then, the brain begins to ignore the images seen by the otherwise healthy eye, and the eye becomes weaker, losing vision strength (acuity). This eye is then referred to as "amblyopic."

What Causes Amblyopia?

A number of things can interfere with normal brain–eye connections and lead to amblyopia.

One of the most common problems is strabismus. In this condition, one or both eyes wander in ("cross-eyed"), out, up, or down. When eyes don't line up together, the straight or straighter eye becomes more dominant. The vision strength of the straight eye stays normal because the eye and its connection to the brain are working normally. The misaligned or weaker eye, though, doesn't focus properly and the brain ignores its signal, eventually leading to amblyopia.

Not all kids with amblyopia will have crossed or wandering eyes — in fact many have eyes that are perfectly straight. If so, amblyopia might be due to an anatomical or structural problem that interferes with or blocks vision, such as a droopy eyelid or a cataract.

Other causes of amblyopia are severe far-sightedness (hyperopia), near-sightedness (myopia), or astigmatism (a form of blurry vision). These problems make vision blurry, and it's these blurry images that are sent to the brain. Over time, the brain begins to ignore these images, resulting in amblyopia in one or both eyes.

Sometimes, having different vision strengths in each eye — known as anisometropia — can cause amblyopia. When one eye sees more clearly than the other, the brain ignores the blurry eye.

Genetics play a role, too. Amblyopia tends to run in families. It's also more common in children born prematurely or those with developmental delays.

What Are the Signs & Symptoms of Amblyopia?

Most children with amblyopia won't complain of vision problems. Over time, they become used to having good vision in one eye and poor vision in the other.

Often, a parent or teacher might realize that a child is struggling with a vision problem — maybe noticing crossed eyes, frequent squinting, or tilting the head to see better. Some kids have poor depth perception and trouble seeing in three dimensions.

Regular vision screenings by health care providers are an important part of finding any problems in kids.

How Is Amblyopia Treated?

Treatment for amblyopia involves forcing the brain to pay attention to the images of the amblyopic or weaker eye so vision in that eye gets stronger. This is done with glasses, eye patches, eye drops, surgery, or a combination of these:

• Glasses. Glasses are prescribed when amblyopia is caused by severe refractive errors and/or anisometropia (when one eye sees more clearly than the other). Glasses help send clear, focused images to the brain, which teach it to "switch on" the weaker eye. This allows the brain to use the eyes together and develop normal vision.
• Eye patches. In many cases, kids with amblyopia must wear an eye patch over the stronger or unaffected eye. The patch is worn for 2–6 hours a day while the child is awake for several months or years, depending on the condition. There are two types of eye patches: one works like a band-aid and is placed directly over the eye; the other, designed for kids who wear glasses, is a cloth patch that fits securely over one lens.
  
  Making sure a child wears the eye patch can be a challenge. But kids usually adapt well, and the patch simply becomes part of their day. In the meantime, distraction with a new or exciting toy, a trip to the park, or just playing outside can help kids forget they're wearing an eye patch.
• Atropine drops. Sometimes, despite parents' best efforts, some kids won't wear their eye patch. In these cases, atropine drops may be used. Just as a patch blocks the vision in the unaffected or straight eye, atropine drops will temporarily blur out the vision in the strong eye, forcing the brain to recognize the images seen by the weaker eye.
• Surgery. If strabismus is causing amblyopia and treatment with glasses, patches, or drops doesn't improve the alignment of the eyes, eye muscle surgery might be an option. Surgery also might be done if amblyopia is caused by a droopy eyelid or a cataract.
  
  Surgery involves loosening or tightening the muscles causing the eye to wander. This type of surgery usually doesn't require an overnight hospital stay.

What Else Should I Know?

Kids reach "visual maturity" by about 8 years old; after that, vision problems can be harder to treat. The earlier amblyopia is diagnosed and treated, the better the chances to improve vision and avoid permanent vision loss.

Eye Exams for Kids

Sometimes there are no signs of a vision problem. So it's important for kids to have yearly vision screenings. These exams should begin in the toddler and preschool years so that problems are caught before a child reaches visual maturity.

Most screenings are done at the pediatrician's office or at school by the school nurse. If problems are found, your child will be referred to a pediatric ophthalmologist for further evaluation and treatment.

Talk with your doctor if you have any questions about your child's vision.