Students in Shanghai spend about three hours a day using electronic devices, and experts there believe that could be what's causing more than half of them to become nearsighted.
In a report by the Shanghai Evening Post cited on the web site China Daily, results from a survey done by Chinese health officials show that almost 60 percent of students in primary and middle school are nearsighted.
Eye doctors in the United States aren't surprised to learn there could be that many students with myopia, or nearsightedness. While studies have shown that the onset of myopia is higher in Asia, experts say that more and more kids worldwide are becoming nearsighted. There's debate over the exact cause and whether it's really due to excessive use of computers and other gadgets with electronic screens.
"In fact, published National Institutes of Health data for the past 30 years find that the incidence of myopia in the U.S. has almost doubled from 24 percent to 42 percent," said Dr. Roy S. Chuck, professor at the Albert Einstein College of Medicine in the Bronx, N.Y.
"Historically, farsightedness was more common than nearsightedness, and that trend has reversed," said Dr. Robert Maloney of Maloney Vision Institute in Los Angeles. "This is a worldwide problem in the developed world, not just a Chinese problem. For example, 90 percent of Singaporean 18-year-olds are nearsighted, and the numbers in Japan are not far off."
As for the reasons behind the widespread increase in myopia across the world, experts say the science is inconclusive.
"The cause is unknown. There were a number of studies done several decades ago that looked at the relation between near work -- like studying and video games -- and nearsightedness, and there wasn't much correlation," Maloney said. "A more recent well-done study published several years ago suggested such a correlation. Bottom line is that we don't know for sure if the video games are causing this."
But, he said, "the onset of myopia in Singaporean 18 year olds preceded the widespread use of video games."
"Although there is no direct definitive evidence, there does exist highly suggestive laboratory and clinical data, and it just makes sense," said Chuck.
A 2008 study published in Opthalmology, the journal of the American Academy of Opthalmology, found showed an association between time spent engaged in outdoor activities and lower rates of nearsightedness among 12-year-old Australian children.
Researchers in that study, led by Dr. Kathryn A. Rose of the University of Sydney in Australia, believe the intensity of outdoor light could play a role, and wrote, "this protective effect suggests that a public health measure aimed at preventing development of myopia could be based on increasing the engagement of children in outdoor activity."
Video Games and Computers May Not Be Entirely to Blame
There could also be other factors contributing to rising myopic rates.
"What we know is that there is a high genetic component to high myopia and that myopia is higher in many Asian countries compared to Western. We also know that myopia is more common in people with higher socioeconomic status and more years of education," said Dr. Jay S. Pepose, director of the Pepose Vision Institute in St. Louis and professor of clinical ophthalmology at Washington University School of Medicine.
Maloney added that more exposure to light because of increased use of electricity is another possible cause.
While experts can't say for sure that too much television or computer time are leading to vision problems in children, they think it's a good idea to curb usage anyway.
"What I always suggest is the proper balance of near and distance vision tasks, that is, get your kids outdoors and experiencing the big world around them," said Chuck.