Eye Disorders: Amblyopia

Amblyopia means poor vision in an eye that did not develop (or is not developing) normal sight during childhood. A child (or adult) with amblyopia will have poor vision in one or both eyes. Amblyopia affects about 2-3 out of every 100 children. Most of the time it is treatable if caught early enough, usually prior to age 8 or so. In adults amblyopia is usually permanent. When amblyopia is diagnosed, it is import to ensure there is no neurological disease present that could also cause blurry vision.

How does normal vision develop?
Newborns and children learn to see by using their eyes. If a clear image is available to an eye, normal vision will almost always develop over the first years of a child's life. If vision develops normally in both eyes, normal binocular vision is able to develop, which will allow depth perception. If a child has normal vision by age 8, they will likely not develop amblyopia.

What goes wrong to cause amblyopia?
In general, amblyopia has three major causes.
   1. Strabismus (misaligned eyes). The child can only look out of one eye. The other crossed eye "turns off" to avoid double vision. Examples of strabismus include esotropia and exotropia.
   2. Refractive errors (need for glasses). If there is a need for glasses in one or both eyes, the child is not seeing clearly, so normal vision can't develop. This is hard for parents to detect, because the child will not complain, and will look normal. Examples could include nearsightedness (myopia), farsightedness (hyperopia), or astigmatism.
   3. Something inside the eye blocking the vision, like a cataract or inflammation. This is also very hard for parents to detect, because the child appears to function normally with one eye.

How is amblyopia treated?
In general two steps are required. First, the underlying cause needs to be treated so the eye can see clearly (for example, glasses). Second, the amblyopic eye needs to be strengthened (for example, with patching or atropine eye drops. Treatment for amblyopia caught early is usually successful. Initial therapy can last months to years depending on the situation. Strabismus surgery, which is surgery to correct misaligned eyes, may also be necessary. There is a risk of relapse, so the child needs to be monitored closely through about age 8.

More information on amblyopia can be found at the National Eye Institute's website.