Babies born in the winter or fall have better long-range eyesight and less chance of requiring thick corrective glasses, says Tel Aviv University's Dr. Yossi Mandel. His fascinating study, published in Ophthalmology, found that babies born in June and July had a 24 percent greater chance of becoming severely myopic than those born in December and January. The study was based on data obtained from 300,000 Israelis aged between 16 and 23.
Study co-author, Prof. Michael Belkin of Tel Aviv University's Goldschleger Eye Research Institute, speculates that the finding likely relates to a long-term effect of early-life exposure to natural light that increases the chances of a child becoming short-sighted. "I am speaking about those people who would have to wear very thick glasses, if they did not use contact lenses or laser surgery for the removal of spectacles."
Separate research conducted on chickens suggests that the body has a mechanism that causes the eyeball to lengthen (short-sighted eyes are longer than normal) when it is exposed to prolonged illumination. This mechanism is associated with melatonin, a pigment secreted by the pineal gland, though scientists are not sure exactly how it operates. "We know that sunlight affects the pineal gland and we have indications that melatonin, through other compounds, is involved in regulating eye length," says Belkin. "More sun equals less melatonin, equals a longer eye which is short sighted."
Belkin doesn't identify any specific evolutionary benefit for extreme myopia in summer babies. "People with longer eyes who lived in the period prior to the invention of eyeglasses were severely disadvantaged and restricted to a few professions or doomed to death." But nowadays, shortsightedness has its advantages, Belkin says, pointing out a strong correlation between myopia and intelligence. "It is not a myth at all that people who wear pop-bottle glasses are smarter. They tend to be," he concluded.
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Source: Tel Aviv University
