Note: The last time I had my driver's license renewed, for the first
time in decades I was able to pass the vision test without wearing
glasses. The clerk asked, "Are you wearing contacts?" I said, "No."
She then asked, "Have you had that surgery?" I said, "No I have just
been eating mostly fruits and vegetables for a long while."
My vision definitely deteriorates when I venture away from the
produce
aisle in the grocery store or am eating mostly restaurant food. And
improves when I eat a diet largely centered around fruits and
vegetables and a few grains.
Tim
Nearsightedness Increasing in U.S.
By Nathan Seppa, Science News
December 15, 2009 |
This broad survey showed that 25 percent of those examined in the
early 1970s were deemed to be nearsighted, compared with 42 percent
examined three decades later, the researchers report in the December
Archives of Ophthalmology. That’s an increase of 66 percent.
Myopia severity also increased, with moderate nearsightedness
doubling
between the two time periods and severe cases, although uncommon,
also
rising sharply. Mild myopia cases increased slightly, from about 13
percent to 18 percent. This group included some people who did not
need corrective lenses, says study coauthor Susan Vitale, an
epidemiologist at the National Eye Institute in Bethesda, Md.
Among blacks, the overall myopia rate was lower than in whites but
still jumped from 13 to 34 percent over the three-decade span.
When analyzing the more recent eye-exam data, the scientists used
only
diagnoses that were made with the same technology used in the 1970s —
mainly standard eye tests and trial lenses. Including diagnoses made
with more advanced technology that has become available only recently
might have biased the comparison, Vitale says.
The cause of nearsightedness is poorly understood. Past research has
linked added risk to both a genetic predisposition to nearsightedness
and to excessive amounts of near work, the kind of tasks that require
peering at written words or small objects.
"Some people would say near work is a reasonable explanation," Vitale
says, particularly with the advent of video games and other
electronic
devices. Children also spend less time outdoors than they once did,
she says. And some researchers contend that more outdoor time means
seeing in better light, focusing farther.
The nature of near work has changed dramatically in the past 30
years,
says Jane Gwiazda, a psychologist at the New England College of
Optometry in Boston who researches vision problems. But while near
work probably accounts for some of the myopia increase, it’s been
difficult to pinpoint the specific detrimental aspect of near work
that’s to blame because the nature of such close work varies. Some
people take frequent breaks or have better lighting than others.
"There are lots of factors there," Gwiazda says.
Meanwhile, compelling data link a lack of outdoor time with increased
myopia risk, she says, with questionnaire-based surveys finding that
children with myopia spend less time outdoors. "Some people think
that
more distance viewing sends a signal to the eye to stop growing," she
says. Nearsighted eyes tend to be elongated. Natural light might also
stimulate dopamine production, which is known to inhibit eye growth,
she says, and extra vitamin D from the sun might contribute to
regulating eye growth.
As for hereditary factors, research shows some added risk for
children
born to nearsighted parents. "It might be that somehow the population
has changed and that there are more people floating around that have
more genetic risk," Vitale says.
Editor’s note: This post was updated to include comment from a
researcher not involved with the study.
http://www.wired.com/wiredscience/20...ss-increasing/...
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