What is Amblyopia?
A common vision problem in children is amblyopia, or ”lazy eye.” It is so common that it is the reason for more vision loss in children than all other causes put together. Amblyopia is a decrease in the child’s vision that can happen even when there is no problem with the structure of the eye.
The decrease in vision results when one or both eyes send a blurry image to the brain. The brain then “learns” to only see blurry with that eye, even when glasses are used. Only children can get amblyopia. If it is not treated, it can cause permanent loss of vision.
Types of Amblyopia
There are several different types and causes of amblyopia: Strabismic amblyopia, deprivation amblyopia, and refractive amblyopia. The end result of all forms of amblyopia is reduced vision in the affected eye(s).
Strabismic amblyopia develops when the eyes are not straight. One eye may turn in, out, up, or down. When this happens, the brain “turns off” the eye that is not straight and the vision subsequently drops in that eye.
Deprivation amblyopia develops when cataracts or similar conditions “deprive” young children’s eyes of visual experience. If not treated very early, these children can have very poor vision. Sometimes this kind of amblyopia can affect both eyes.
Refractive amblyopia happens when there is a large or unequal amount of refractive error (glasses strength) in a child’s eyes. Usually, the brain will”turn off” the eye that has more farsightedness or more astigmatism. Parents and pediatricians may not think there is a problem because the child’s eyes may stay straight.
Also, the “good” eye has normal vision. For these reasons, this kind of amblyopia in children may not be found until the child has a vision test. This kind of amblyopia can affect one or both eyes and can be helped if the problem is found early.
Causes & Symptoms
Amblyopia occurs when the brain and eyes do not work together properly. In persons with amblyopia, the brain favors one eye.
The preferred eye has normal vision, but because the brain ignores the other eye, a person’s vision ability does not develop normally. Between ages 5 and 10, the brain stops growing and the condition becomes permanent.
Strabismus is the most common cause of amblyopia, and there is often a family history of this condition.
Other causes include:
- Astigmatism in both eyes
- Childhood cataracts
- Eyes that turn in or out
- Eyes that do not appear to work together
- Inability to judge depth correctly
Treatment & Prognosis
Amblyopia is usually easily diagnosed with a complete examination of the eyes. Special tests are usually not required.
One of the most important treatments of amblyopia is correcting the refractive error with consistent use of glasses and/or contact lenses.
Other mainstays of amblyopia treatment are to enable as clear an image as possible (for example, by removing a cataract), and forcing the child to use the nondominant eye (via patching or eye drops to blur the better-seeing eye). Sometimes, drops are used to blur the vision of the normal eye instead of putting a patch on it.
The underlying condition will also require treatment. For the treatment of crossed eyes, see: Strabismus
Children whose vision cannot be expected to fully recover should wear glasses with protective lenses of polycarbonate, as should all children with only one good eye caused by any disorder. Polycarbonate glasses shatter and scratch-resistant.
Children who receive treatment before age 5 usually have a near-complete recovery of normal vision. Delaying treatment can result in permanent vision problems. After age 10, only a partial recovery of vision can be expected.
Possible complications include eye muscle problems that may require several surgeries and permanent vision loss in the affected eye.