Amblyopia is a condition that occurs in children when one eye has poorer vision than the other. If amblyopia is left untreated, a child's vision will not develop correctly. The child's brain, as it matures, will start "ignoring" the image coming from the bad eye. This causes vision in the affected eye to become even worse as the child becomes a teenager. Because amblyopia can result in permanent vision loss in one eye, it is important to have a child with amblyopia regularly tested by an eye doctor.
What Causes Amblyopia?
Amblyopia is usually starts when one eye has much better focus than the other eye. For example, one eye might be very nearsighted or have a lot of astigmatism , while the other does not. When the child's brain is confronted with both a blurry image and a clear image, it will begin to ignore the blurry image. If this goes on for months or years, the vision in the eye that sees the blurry image will start to deteriorate even further. Another possible result of the brain ignoring the poorly functioning eye is a change in the alignment of the eyes, with the poorly seeing eye turning inwards or outwards. This is why amblyopia is sometimes called "lazy eye."
Another form of lazy eye that can cause amblyopia is called strabismus. Strabismus or ocular misalignment prevents the eyes from focusing together on an image. This can cause double vision. In order to combat this, the child's brain generally chooses to ignore the image from the deviated eye, causing the vision in that eye to eventually deteriorate.
Other children cannot see well in one eye because there something blocks light from getting through. This could be due, among other causes, to a cataract or a small amount of blood or other material in the back of the eye.
How Is Amblyopia Diagnosed?
Your child's pediatrician or the vision program at school will check three aspects of your child's eye health:
- That your child's eyes let light all the way through
- That both eyes see equally well
- That the eyes are moving normally.
How Is Amblyopia Treated?
The most common treatment for amblyopia is to force the brain to start using the "bad" eye by putting a patch over the "good" eye. At first, the child will have a hard time seeing with just the weaker eye. However, it is very important that your child wear the patch diligently because this will eventually improve vision. It can take weeks, months, or even a year for an eye patch to improve vision.
As the child keeps using only the eye with amblyopia, his or her vision will continue to improve. After the doctor determines that vision is back to normal, your child will not have to wear the patch. In cases of mild amblyopia, the doctor might recommend using an eye drop called atropine in the "good" eye instead of a patch. Atropine makes it impossible for that eye to focus close-up, forcing the "bad" eye to do most of the work while the child is playing with toys, eating, drawing or reading.
If there is something blocking light from getting into the eye, the doctor might recommend surgery to remove the blockage. If strabismus is preventing the eyes from moving together correctly, your doctor might recommend surgery on the muscles of the eye. And if the focus of one eye is very different from the other, eyeglasses or contact lenses might be necessary.
Your doctor will discuss with you what treatment is most appropriate for your child.
What Is the Outlook for Children With Amblyopia?
If existing underlying problems are treated and the amblyopia is detected and treated early, most children will regain normal vision. Amblyopia becomes much more difficult to treat after about 6 years of age. Also, if there is too much vision lost in the eye with amblyopia, it might be impossible to get it all back.
It is important that you follow your doctor's advice about treatment. This can be very difficult, because many children do not want to wear an eye patch every day. But with the establishment of atropine as an alternative method of treatment, success is now possible in a larger proportion of children with amblyopia.
Reviewed by the doctors at The Cleveland Clinic Cole Eye Institute.
Edited by Charlotte E. Grayson, MD, WebMD, October 2004.