Amblyopia (Lazy Eye)

In some children sight does not continue to develop properly in one eye even though that eye is structurally normal. The condition is called amblyopia (am-blee-oh-pee-uh) or “lazy eye,” because the eye seems to have lost the desire to see.

What Causes Lazy Eye

Each eye sends a slightly different visual image to the brain.  Normally, the images are similar enough to allow them to be combines into a single image by the brain.  If the two images are too different from one another, the brain cannot combine them and the result is double vision.  Young children are able to avoid double vision by suppressing (actively ignoring) the image from one eye.  Eventually the eye that suppresses images loses its ability to see clearly.

Why are there two images

The most common conditions that can cause the eyes to send different visual images to the brain are strabismus (misaligned eyes; one looks straight ahead while the other turns in, out, up or down) and anisometropia (ann-eye-so-meh-troh-pee-uh) which means that the two eyes have very different optical powers (for example, one may be normal and the other very farsighted or have extreme astigmatism).

Even if you can tell that your child has one of these conditions along with poor vision, you still have no way, on your own, of knowing whether one eye is “lazy”.

Treatment and Prognosis

Treatment must begin before school age to give the amblyopic eye the best chance of regaining normal vision.  After the age on nine, the possibility of reversal is passed and amblyopia will remain for life.

If the cause of the lazy eye is an optical one, it will be treated first.  Prescription eyeglasses may be necessary (eyeglasses can be worn by infants as young as a few months old).  Although vision may improve somewhat with the glasses, it will continue to be poorer than in the normal eye.

If the eyes are misaligned, surgery may be necessary to straighten them.  Surgical success is enhanced when the vision in both eyes is normal so surgery will be delayed until the amblyopia has been treated.

One the basic cause of amblyopia has been identified and treated, a vigorous program of “patching” (covering the good eye is necessary so that the child will use the amblyopic eye.   It will take a lot of urging and patience since you will be forcing the child to use and eye that sees poorly.  (The patching does not correct any eye misalignment or eliminate the need for prescription eye glasses.)  When the patch is on the “good straight” eye, the amblyopic eye straightens to the normal position for focusing.  Most parents do not realize that the “good” eye under the patch then deviates.  Also, penalization with dilating drops to blur the image in the better eye can be used in some patients.