Too much screen time may be damaging children’s eyesight

There is new evidence that spending too much time using digital devices could hurt children's eyesight. A study published in the journal PLOS One finds school-aged children who spent seven hours or more a week using computers or mobile video games tripled their risk for myopia, or nearsightedness.

Rates of myopia have increased worldwide in recent years. In the United States and Europe, nearly half of young adults have the condition -- double the prevalence of 50 years ago. Rates are even higher in Asia.

One reason for this is the increasing amount of time kids are spending in front of screens.

"The reason why that's a problem is not so much that the device is sending some magic signal to the eye that's damaging it, it's that when you're on those devices you tend to be inside and not outdoors in the sunlight," Dr. Christopher Starr, an ophthamologist at Weill Cornell Medical Center in New York City, told "CBS This Morning." 

Sunlight plays an important role in protecting vision, as it triggers dopamine, a neurotransmitter which keeps the eye from getting too elongated during childhood.

"So as the eye is maturing, if it stretches too long it becomes more and more nearsighted. So the dopamine actually prevents that," Starr explained.

Some estimates show that children between the ages of 2 and 8 spend an average of two to three hours a day on screens.

So far, the only antidote believed to protect children's eyes is for them to spend less time on screens.

"It's really about limiting the time and encouraging them to get outside in the sun," Starr said. "No screen protector is going to make any real difference."

And while sitting too close to the television won't damage eyesight -- that's an old wives' tale -- it may be a warning sign that your child is suffering from myopia.

Other signs include squinting and loss of attention.

"If they used to be very interested in reading or drawing and all of a sudden they're not interested or if they're reading and keep losing their place, those are signs that there might be a vision problem," Starr said.

In fact, sometimes children may be misdiagnosed with learning disabilities such as ADHD or dyslexia, when it's really a vision problem that's hampering them in school.

"Learning is 80 percent visual, if you think about the way we traditionally learn, looking at boards, reading, homework," Starr said. "You need good vision to learn."