Dec. 16, 2009 — -- Don't look now, but you could be, right at this instant, contributing to a growing problem in America: nearsightedness.
A new study conducted by the National Eye Institute shows that the rate of nearsightedness, or myopia, in Americans has increased from 25 percent in the 1970s to a staggering 41 percent this year.
The study didn't examine the causes of such an increase, but experts told "Good Morning America" the reasons could include genetics or poor outdoor lighting. Another possible reason could be an increase in "near work"-like reading, surfing the Web or texting.
"Nearsightedness work can really affect the development of young eyes," said Dr. Roy Chuck, chairman of ophthalmology at Montefoire Medical Center in New York. "If that is exclusively the kind of work that you are doing, it is equally important to be outside playing, stimulating your far vision."
Though the study's author, Susan Vitale of the National Eye Institute, said more research is necessary, she added that identifying the problem was important.
"It was really good to be able to confirm this was going on," Vitale said. "While myopia is pretty easily treated, when a lot of people -- 40 or 50 million people -- it ends up costing the U.S. about $2 to $3 billion annually. So it's an important problem if it's on the increase."
Dr. Richard Besser, ABC News' Senior Health and Medical Editor, said myopia is genetic.
"If your parents were nearsighted there is a good change that you're going to develop nearsightedness," Besser said.