The most common cause of vision loss in childhood is a condition called amblyopia. It can affect one or both eyes, causing vision to be decreased, fussy, or even completely lost.
In a child affected with amblyopia, one eye does not see as well as the other eye, causing the image that is transmitted from the eye, along the optic nerve to the brain, to be abnormal and different from the image from the other eye. As it is difficult for the brain to interpret two different images, it tells the optic nerve to stop sending messages. In effect, the brain tells the healthy nerve to shut itself off. Over time, the nerve does not develop and the damage becomes permanent. The child is left with a loss of vision in the affected eye forever.
There are many causes of amblyopia, but the most common is strabismus. Strabismus is a misalignment of the muscles of the eye that prevents the eyes from lining up correctly. Strabismus can be very obvious, appearing as a crossed eye or as an unnatural turn out of one eye, or it can be very subtle. Strabismus runs in families. Strabismus can be corrected, a process that usually starts with prescribing eyeglasses. Occasionally, a surgical procedure to correct an ocular muscle is necessary. Other causes of amblyopia include congenital cataracts, farsightedness, nearsightedness, and astigmatism.
When found early, amblyopia can be treated. Often in children, this is accomplished by patching the stronger eye for hours each day. Patching the normal eye forces the weaker eye to be used, increasing the visual images that are transmitted through the optic nerve to the brain. According to the National Institutes of Health, when amblyopia treatment is begun prior to age five, most children will recover near-normal vision. While patching seems like an impossible task in a toddler, children usually tolerate it very well and learn to leave the patch undisturbed for the prescribed amount of time.
Children should have their eyes evaluated at each well-child visit. Any concerns should be brought to their doctor’s attention and a family history of strabismus or amblyopia discussed. A simple ophthalmologic exam can diagnose both strabismus and amblyopia and is easily accomplished even in a small child by an experienced ophthalmologist. Some pediatricians are now using a computerized screening device in their office to better screen children for amblyopia, allowing children with subtle findings to be diagnosed and referred to as an ophthalmologist even earlier than in the past.
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