Sydney, Oct 9 (IANS): Nearly one billion people could be at risk of blindness by the middle of the century if an emerging short-sightedness (myopia) epidemic is ignored, said researchers.

Half the world's population (around five billion) will be myopic by 2050, they predict, with up to one-fifth of them (one billion) in the high myopia category and at a significantly increased risk of blindness.

Currently, it is estimated that over two billion people in the world suffer from myopia.

"We are calling on the world to protect the eye health of every child and adult and meet this major public health challenge of our time," said professor Kovin Naidoo from the Brien Holden Vision Institute, Australia.

Myopia has become particularly prevalent in East Asia where in urban areas of Singapore, China, Taiwan, Hong Kong, Japan and South Korea the prevalence is 80-90 percent among school students.

In Western countries like the US, the rate has risen markedly in adults in the last 30 years, from 25 percent in the early 1970s to 42 percent in 2004.

"Myopia is not curable or reversible, but there are promising interventions using optical and behavioural approaches that can help slow the progression and prevent people becoming highly myopic," Naidoo said.

"Parents should encourage their children to spend time outdoors for at least two hours each day," he advised.

"They should also ensure children don't spend too much time on electronic devices, such as tablets, mobile phones, electronic games, television and other activities which requires them to focus close up for long periods," he added.