Babies born in the summer are more

Babies born in the summer are more likely to become shortsighted in their later lives,a study has shown.As many as a quarter of all cases of shortsightedness are caused by too much exposure to the sunlight in the first weeks of their lives,say eye experts.They are advising that all babies should be put on sunglasses by their parents during the first weeks.Scientists have already found that over-exposure to the sunlight causes shortsightedness in animals.Researchers,who compared the months in which babies were born with whether they needed glasses later on,say the principle also applies to humans.A study of almost 300,000 young adults showed that those born in June and July had more chances of becoming severely shortsighted than those born in December or January.Research leader Professor Michael Belkin,of Tel Aviv University,said it was because prolonged exposure to the sunlight causes eyeballs to lengthen—causing shortsightedness.Therefore the more sunlight a newborn baby is exposed to,the more its eyeballs lengthen and the worse its shortsightedness will be.The mechanism which lengthens the eyeballs is associated with levels of melatonin(褪黑激素),a pigment(色素)which protects the skin against harmful rays of the sun.In newborn babies not enough melatonin is released as protection,which means they are more vulnerableto sunburn and changes of the eyeball shape.Sight expert Professor Daniel O’Leary,of Anglia Ruskin University in Cambridge,said,“At the moment we don’t know the precise cause of why exposure to the sunlight affects sight,but the evidence seems to prove that it is one of the reasons for people becoming shortsighted.”