Exposure to sunlight may increase the risk of developing cataracts, scientists have found.

Cataracts are the leading cause of blindness world-wide.

Researchers studied 2,584 residents of the French town of Sete.

They found people who were exposed to high levels of sunlight, or solar radiation, were up to four times more likely to develop cataracts.

The researchers, led by Dr Cecile Delcourt, from the Institut National de la Sante et de la Recherche Medicale (INSERM), said: "It seems that sunlight exposure throughout a lifetime may be important to cataract formation."

The greater the dose of solar radiation, the higher the chance of developing a cataract.

A cataract is a cloudy or opaque area in the normally transparent lens of the eye.

As the opacity thickens, it prevents light rays from passing through the lens and focusing on the retina, the light sensitive tissue lining the back of the eye.

Childhood exposure

It is thought that the ultra-violet component of solar radiation may speed up the clouding of the lens.

Dr Delcourt told BBC News Online: "We have little data concerning the ways to reduce the sunlight-related risk of cataract.

"However, I would advise mostly avoiding sunlight exposure at midday, wearing a hat and sunglasses.

"I would also like to stress the fact that, in ours and previous studies, the effect of sunlight seems to be cumulative.

"Exposure during childhood is at least as important as exposure during adulthood."

Mr Jonathan Dowler, a consultant ophthalmic surgeon at Moorfields Eye Hospital, said previous research had also linked cataract formation to light exposure.

He said: "This research offers the prospect of simple preventative measures.

"This is particularly important in an increasingly elderly population."

The research is published in Archives of Ophthalmology.