Helping the Weaker Eye

Although babies can see from the moment they are born, they can do little more than distinguish light from dark and make out shapes. Over time, their vision develops, and by about 6 months they’re able to identify and distinguish between objects. (It isn’t until at least 7 years old, however, that vision reaches what is considered to be normal vision.)

Normal visual development requires that the brain receive equally clear, focused images from both eyes simultaneously. When images from one eye are out of focus, the brain responds by ignoring, or “turning off,” that eye. A cataract that clouds the lens in one eye, for example, can cause the brain to do this; a significant refractive error (the sight in one eye is better than in the other eye) can as well. The same thing occurs if the eyes send two mismatched images to the brain, even if both images are clearly focused--such as when the eyes are misaligned.

Although this strategy is effective in producing a clear, focused image, the eye that is ignored grows weak with disuse and can go on to develop permanent loss of vision.

To prevent that from occurring, the underlying cause of the problem must be treated. For example, glasses may be required to correct a refractive error; an eye patch can strengthen a weakened eye (by covering the strong eye, the brain is forced to pay attention to the weak one); and surgery can remove a cataract or correct misalignment.