Research by Australian scientists has shown that spending two or three hours a day outdoors dramatically reduces a child's risk of becoming short-sighted. This, they claim, is because sunlight triggers the release of chemicals that prevent distortion of the eyeball and cause myopia.

Advocates of the more old-fashioned, Hairy Palm Theory of diminished eyesight will simply see it as proof that little Australian boys are too shy to masturbate outdoors.

http://www.timesonline.co.uk/tol/comment/columnists/giles_coren/article5484660.ece

(Scroll 2/3 of way down in the article linked.)