Lower-income students in China found to have better vision than middle-
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In one of the largest population-based studies ever conducted on
nearsightedness in children, researchers have discovered that lower-
income students in China have better vision than their middle-class
counterparts. Data show that nearsightedness, also called myopia, is
twice as prevalent in the middle-income province of Shaanxi compared to
the poorer neighboring province of Gansu. The study was published online
in Ophthalmology, the journal of the American Academy of Ophthalmology.
In certain developed parts of East Asia, nearsightedness is
skyrocketing, with the prevalence of myopia now at an estimated 80 to 90
percent of the population.1 In areas of the world where families cannot
afford eyeglasses, poor vision from nearsightedness is a serious
disability that can affect a person's ability to learn and work.
Globally, 13 million children worldwide - about half of them in China -
are visually impaired because of poor sight not corrected by glasses or
other means, according to the World Health Organization. With those
factors in mind, research teams have been scrambling to find an answer
to the Asian "school myopia" crisis.
To manage this public health issue, multiple Chinese government agencies
and universities, together with experts from Stanford University, have
undertaken several large studies on childhood myopia. In 2012, they
examined vision in nearly 20,000 fourth- and fifth-grade students: 9,489
students in Shaanxi, a middle-income province, and 10,137 students in
Gansu, the second poorest province in China. The findings include the
The prevalence of clinically significant myopia2 in the middle-
income province of Shaanxi is almost 23 percent, nearly twice that of
the lower-income province of Gansu, which has a 12.7 percent prevalence
rate of myopia.
Living 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's parents wore glasses.
Higher math scores were associated with increased myopia in all
Nearsightedness was less prevalent in males overall.
The research team also looked at whether the use of blackboards, as
opposed to textbooks, played a role in staving off myopia. Students in
the lower-income area rely more on blackboards to learn in the classroom
as they may have difficulty affording books, while students in the
middle-income areas used blackboards less often. Researchers found that
using blackboards had a "protective effect" against nearsightedness when
examined as a variable alone, possibly because blackboards do not
require the kind of close-up focusing that may increase myopia. However,
when adjusting for other factors, they found no statistically
significant differences between lower-income and middle-class students
that might explain higher myopia prevalence in richer areas.
"We're 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," said the project's lead
investigator Professor Nathan Congdon, M.D., MPH, of the Zhongshan
Ophthalmic Center at Sun Yat-sen University in Guangzhou, China. "What's
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."
Previous studies have found that people who had higher levels of
education and years spent in school were more likely to be nearsighted.3
Many researchers also postulate that exposure to certain kinds of light,
particularly indoor versus outdoor light, may be responsible for the
uptick in myopia. Recent studies of children and young adults in Denmark
and across Asia show that more time outdoors and exposure to daylight is
associated with less nearsightedness.4
For more information on myopia, visit the American Academy of
Ophthalmology's public education website www.geteyesmart.org
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