ROBERT SIEGEL, HOST:
If you walk the streets of China today, you quickly notice something - most young people wear glasses. In Shanghai for instance, 86 percent of high school students suffer from myopia, or nearsightedness. The American Academy of Ophthalmology published a new study on the topic today. But researchers are still trying to figure out what's driving the epidemic. NPR's Frank Langfitt reports from Shanghai.
FRANK LANGFITT, BYLINE: Chinese parents have a lot to worry about when it comes to their children's health - air pollution, unsafe food. A Shanghai woman named Wang says she fears her 4-year-old daughter will develop myopia. After all, her 10-year-old nephew already suffers from it.
WANG: (Through interpreter) I'm worried. Of course I'm worried. Sometimes when parents don't have time to play with their children, they'll throw a cell phone or an iPad to the kids to let them play. Kids would become totally absorbed in these games. And I think this is very damaging to their eyes.
LANGFITT: That's one theory. Research shows myopia in general is linked to urbanization, higher incomes and education, and has risen quickly in much of East Asia. He Mingguang is a Chinese ophthalmologist and leading myopia researcher. He says studies suggest China's crushing homework load is putting too much strain on kids' eyes. He describes a 10-year-old's typical week night.
HE MINGGUANG: For most of the kids - if they're in an urban setting - after supper, like, 7 p.m. Then they should work on homework and writing until 11:30 to 12.
LANGFITT: He, who now works at the University of Melbourne, says changing habits here is hard because Chinese society is so competitive. School kids are forced to spend countless hours studying for the country's do-or-die college entrance exam, the dreaded gaokao.
MINGGUANG: In the perspective of a lot of Chinese parents, they think if you fail the university gaokao, then their children won't have good careers.
LANGFITT: Another study, which focused on young Chinese students in Singapore and Sydney, suggests more time outdoors in the sun might help. Students surveyed in both countries spent similar amounts of time studying, but 29 percent of the Singaporean students had myopia, compared with just 3 percent in Sydney. Ian Morgan, a biological researcher, co-authored the 2008 study.
IAN MORGAN: The big difference was the Chinese children in Australia were outdoors a lot more than their sort of matched peers in Singapore. And this was the only thing that fitted with the huge difference in prevalence.
LANGFITT: Morgan thinks sunlight may stimulate the release of dopamine from the retina and inhibit the elongation of the eye that results in myopia. Many Chinese children with myopia don't wear glasses and just struggle. Not because of the cost - a decent pair of glasses costs just five bucks here - but because some Chinese distrust spectacles. Nathan Congdon, a professor at Zhongshan Ophthalmic Center in the southern city of Guangzhou explains.
NATHAN CONGDON: Parents, teachers and even some rural doctors think that wearing glasses will harm kids' eyes.
LANGFITT: Congdon's working to change that with more education so more children here will at least be able to read a blackboard. Frank Langfitt, NPR News, Shanghai.