Justin Williams, 6, is a healthy, energetic boy who likes to watch cartoons, ride his bike, play on the computer and horse around with his two brothers, ages 8 and 15 months. But the treatment he receives for an eye condition keeps him from enjoying these activities – or much of anything – up to eight hours a day.

In fact, he recently was in the car with his folks when his dad suddenly hit the brake, apparently – to Justin, anyway – for no reason. His mom, Jessica Williams, of Kalispell, Mont., recalls Justin shouting from the back seat, "What are you waiting for, Dad? Go!" "When I told him there were tons of cars in front of us, he shrugged his shoulders and said, 'I don't see any cars,'" Williams says.

Justin was diagnosed with amblyopia, or "lazy eye," the most common cause of visual impairment in childhood, according to the National Eye Institute (NEI), an arm of the U.S. Department of Health and Human Services' National Institutes of Health.

Up to 5 percent – five out of 100 – of American babies and young children develop lazy eye. "[It] is a condition of poor vision in an otherwise healthy eye because the brain has learned to favor the other eye" due to crossed or wandering eyes or those with severe nearsightedness or farsightedness, the NEI reports. If left untreated, amblyopia can result in vision loss in the "lazy" eye. But it can be treated, often very successfully. The key lies in early detection and consistent treatment.

There was no indication prior to his first, yet routine, eye exam that Justin had any vision problems. His mother says he performed just fine in school, as well as on the playground.

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