Yael: I've heard people say that reading a lot causes near-sightedness. Is there any truth      to that?

Don: That's a good question. The exact causes of near-sightedness, or myopia, have      been debated by scientists for a long time. Some are convinced that the condition is      hereditary, while others point to environmental factors as the culprit.

Y: So, it's a nature vs. nurture question, eh?

D: That's right. On the one hand, some researchers insist that this condition is all in the      genes, and that you have mom and dad to thank for those glasses. A study      conducted by scientists in the United Kingdom measured the eyeball size of four-      hundred sets of twins. Using mathematical modeling techniques, they found that      eighty-nine percent of refractive vision problems like myopia can be attributed to      genetic factors.

Y: Wow, that's pretty convincing.

D: On the other hand, there's also evidence that rates of literacy and myopia are linked,      so that when more people in a given population are able to read, the number that      become nearsighted also goes up. One famous study of the Eskimos in Alaska found      that myopia increased considerably when their children began attending school and      doing a lot more reading.

Y: So, should I cut down on my reading to save my eyes?

D: No, that won't be necessary. While close-up work like reading seems to play some      role in the development of myopia, the most significant factor continues to be      heredity. If your parents are nearsighted, you probably will be, too.  

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