Research Suggests that "Lazy Eye" in Adults May Be Treatable
Amblyopia, or "lazy eye," is characterized by poor vision in one eye that is not the result of a structural abnormality. This problem cannot be corrected with glasses or contact lenses, as it is not a problem with the eye itself, but rather with how the brain interprets input from that eye. Lazy eye is very common, affecting about six million people in the United States.
Amblyopia occurs when vision is impaired in one eye during early childhood (birth to age six). When one eye sees clearly and the other does not, the brain learns to ignore the images from the impaired eye, resulting in a permanent vision decrease in that eye.
The most common cause of amblyopia is strabismus, or deviating eyes. When one of a child's eyes turns inward, outward, up, or down, the eyes cannot be aimed at an object properly, resulting in double-vision. To prevent this double-vision, the brain will begin to suppress images from one eye.
Other causes of lazy eye include anisometropia (where one eye is more nearsighted or
farsighted than the other) and blockage of the eye, such as from trauma, lid problems, or cataracts.
To treat amblyopia, vision in the good eye is obscured, forcing the brain to use images from the weaker eye. This is usually accomplished with an eye patch, though in some cases, atropine drops are used instead. The drops dilate the eye, blurring vision. This may be advantageous with children who insist on removing the patch, however this treament can have side effects, such as light sensitivity (from the constant dilation).
For some children, vision therapy or glasses may also be needed.
Treatment for Older Children
For many years, doctors believed that treatment was only possible in young children, that after a certain point in development, the brain structure was permanent and could no longer be retrained. Recent studies have disproved this and shown that treatment is effective in older children as well. Traditional therapy has been proven effective up to age 17, however treatment should be sought as early as possible for the quickest recovery and best possible results.
New Hope for Adult Sufferers
New research has shown that the adult brain has more plasticity than previously thought. Doctors have found that repetitive transcranial magnetic stimulation (rTMS) can temporarily improve contrast sensitivity in adult amblyopia patients. Fifteen minutes of rTMS therapy resulted in improved vision for at least 30 minutes. They are optimistic that repeated doses may result in longer-lasting improvement or make the brain more receptive to vision therapy.
The researchers are unsure exactly how rTMS works, though it is believed to affect the balance of excitation and inhibition in the brain. The treatment is already used to aid recovery after a stroke and its effects on depression are being studied.
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