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Am Fam Physician. 1999;60(3):918

See related article on the eye in childhood.

What is amblyopia?

Amblyopia (say this: am-blee-oh-pee-ah) is an eye problem that causes poor vision in children. The problem starts when the pathways of vision in the brain don't develop, or grow, strong enough. Pathways are a little like roads—they carry vision messages from eye to brain. Amblyopia is also called “lazy eye.”

What causes amblyopia?

All babies are born with poor eyesight. As babies grow, their eyesight gets better. Good eyesight needs a clear, focused image that is the same in both eyes. If the image isn't clear in one eye, or if the image isn't the same in both eyes, the vision pathways won't develop right. In fact, the pathways may actually get worse.

Anything that happens to blur the vision or cause the eyes to be crossed during childhood may cause amblyopia. For example, the image might be different in both eyes if the child has strabismus. Strabismus (also called “crossed eyes”) causes the eyes to not focus the same. Children who need glasses to see better, or have cataracts, a droopy eyelid, or crossed or wandering eyes may also get amblyopia. About 5% of children have amblyopia.

How is amblyopia treated?

Because there are several causes of amblyopia, the treatment must match the problem. Glasses fix some problems. Surgery may be needed for cataracts, droopy eyelids or crossed eyes. After the cause of the amblyopia is found, the child will need to use the weaker eye most of the time, so it will get stronger. To make the child use the weaker eye, a patch can be put over the stronger eye. Sometimes, eye drops or special glasses are used to blur the vision in the stronger eye. This makes the weaker eye become “stronger.” Patches may be used all day or part of the day, depending on the child's age and vision.

The treatment usually lasts until vision is normal, or until vision stops getting better. For most children, this takes several weeks. A few children need to use eye patches until they are eight to 10 years old.

Why is early treatment important?

The vision pathways in the brain must become strong early, when children are very young. The first few years of life are the most important for eyesight. After a child is eight to 10, the brain's vision system is all grown up—it's complete. It can't develop anymore. If the amblyopia hasn't been treated by this age, the child will have poor vision for life. It won't be possible to fix it with glasses, patching or any other treatment.

There's a small chance that using an eye patch for too long can hurt the strong eye. For this reason, children who are wearing eye patches should see their doctor often during the treatment.

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