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:

Lifestyle Blamed for Rise in Myopia in East Asia

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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