Poor vision more common in richer families
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A STUDY involving 20,000 children in China says that those in poorer families were far less likely to be nearsighted than their wealthier counterparts.
Myopia, was twice as prevalent in the middle-income province of Shaanxi in China鈥檚 northwest 鈥 where students have greater access to books 鈥 compared to the poorer neighboring province of Gansu, according to research published in Ophthalmology, the journal of the American Academy of Ophthalmology.
Researchers said the findings were based on one of the largest population-based studies ever conducted on nearsightedness in children.
The team included Chinese government agencies and universities and experts from Stanford University in California. They tested the vision of fourth and fifth grade students, those in the 9 to 11-year-old range.
More than 9,400 students were in Shaanxi, and more than 10,100 in Gansu, the second poorest province in China.
Nearly 23 percent of youths in Shaanxi had clinically significant myopia, almost twice that of Gansu, which had a 12.7 percent prevalence rate of myopia.
鈥淟iving in the middle-class area was associated with a 69 percent increased risk for nearsightedness, even after adjusting for other risk factors, such as time spent reading, outdoor activity and whether the student鈥檚 parents wore glasses,鈥 said the study.
Doing well at math, which requires intensive focus on a written page, was among the factors linked to higher incidence of myopia.
Girls were also more likely than boys to be nearsighted.
One idea researchers had is that the poorer schools鈥 use of blackboards as a teaching tool may have had some protective effect against myopia, but this association disappeared when researchers controlled for other factors such as family history and outdoor play.
鈥淲e鈥檙e still on the hunt for a plausible explanation and think the results merit more study into whether using blackboards versus books may be partially responsible for protecting eyes against nearsightedness, and what other factors may play a role,鈥 said lead investigator Professor Nathan Congdon of the Zhongshan Ophthalmic Center at Sun Yat-sen University in south China鈥檚 Guangzhou, .
鈥淲hat鈥檚 important is that we figure out how lower-income Chinese students have avoided nearsightedness so we can use those same strategies to prevent more childhood myopia cases across Asia and perhaps even the world.鈥
Myopia has been rising rapidly in some developed parts of East Asia, where the prevalence of myopia has reached 80 to 90 percent of the population.
Studies in Asia and Denmark have shown that nearsightedness is less common in children who spend more time outdoors and are exposed to more natural daylight.
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