How Do People Get Nearsighted?
Hereditary or genetic mechanism plays
an important role of causing the vision problem. However, there's evidence that one major environmental
contributor is close-up work.
Researchers have observed that an increased literacy rate in a
population is often followed by a dramatic rise in the rate of myopia, says
Karla S. Zadnik of Ohio State University's College of Optometry in Columbus.
When we do close-up work, such as
reading, using computers, watching TV, the eye muscles that work with cornea
and lens become intense, and the eyeball elongates to make the image form
exactly on the retina. If this
situation lasts for too long, the eye muscles cannot relax any more, and the
misshaping becomes permanent, and we get Myopia.
Do parents who became myopic because of
heavy reading create an environment that encourages their kids to follow suit,
she asks. Or do kids inherit a genetic propensity for myopia, and reading
triggers it?
Here is a recent article from London:
http://news.yahoo.com/news?tmpl=story&u=/nm/20040707/hl_nm/health_myopia_dc_1
Wed. Jul 7, 2004
LONDON (Reuters) - A rise in myopia, or
nearsightedness, in east Asia is due to lifestyle changes and not genetics, a
science magazine said on Wednesday.
Genetic variations that make people more susceptible
to myopia were thought to be the cause of the increase in the vision problem in
countries such as Singapore and Japan where cases have risen sharply.
But Ian Morgan, of the Australian National
University in Canberra, said there is no evidence to support the genetic theory
and added that the rise in myopia is due to lifestyle changes, particularly
hours spent indoors reading or in front of a computer or television.
"Children now spend much of their time focusing
on close objects, such as books or computers," New Scientist magazine
said. "To compensate, the eyeball is thought to grow longer. That way less
effort is needed to focus up close, but the elongated eye can no longer focus
on distant objects."
People with myopia have difficulty seeing objects at
a distance, or reading signs but can do close-up tasks and read.
The magazine said the rate of myopia in India is
about 10 percent but that 70 percent of 18-year-old men of Indian origin in
Singapore have myopia.
Morgan and Kathryn Rose, of the University of Sydney,
also cited a study in Israel which found that 80 percent of teenage boys
studying in religious schools that emphasized reading texts had myopia,
compared to 30 percent in state schools.
"As
kids spend more time indoors, on computers or watching telly, we are going to
become just as myopic," said Morgan.
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