Babies born in summer are more likely to becomeshort-sighted in late life,a study has shown.
As many as a quarter of all cases of shortsightedness are caused by too great an exposure to sunlightin the first weeks of life,say eye experts.
They are advising all parents to put sunglasseson their babies during the first weeks.
Scientists had already established that overexposure to sunlight caused short-sightedness inanimals.
Researchers who compared the months in whichbabies were born with whether they needed glasseslater on say the principle also applies to humans.
A study of almost 300 000 young adults-thelargest of its kind-showed that those born in June orJuly had a 25 percent greater chance of becomingseverely short-sighted than those born in December orJanuary.
Research leader Professor Michael Belkin,of TelAviv University,said it was because prolongedillumination(光照) causes the eyeball to lengthen,causing short-sightedness.
Hence the more light a newborn is exposed to,the more the eyeball lengthens and the worse theshort-sightedness will be.
The mechanism which lengthens the eyeball isassociated with levels of melatonin,apigment which protects the skin againstharmful rays of the sun.
In young babies not enough metatonin is releasedas protection,meaning they are more vulnerable tosunburn and changes to eyeball shape.
Sight expert Professor Daniel O'Leary,of AngliaRuskin University in Cambridge,said," At themoment we don't know the precise cause of why lightexposure affects sight,hut the evidence proves that itis one of the reasons for people becoming short-sighted. "