Scientists say lack of access to sunlight has led to a significant rise in myopia (short- sightedness) among children in east Asian cities.
Researchers from the Australian National University found that up to 90% of school leavers in urban areas are short-sighted.
The BBC reports that they say the problem is being caused by students working very hard in school and missing out on outdoor light.
They told the Lancet that up to one in five of these students could experience severe visual impairment and even blindness.
According to Professor Ian Morgan, from the Australian National University, told the BBC that 20% - 30% was once the average among people in South East Asia.
Cultural factors also seem to play a part. Across many parts of South East Asia, children often have a lunchtime nap. According to Professor Morgan they are missing out on prime light to prevent myopia.
''Children suffer from a double whammy in South East Asia,'' said Professor Morgan.
''As a result of massive educational pressures and the construction of a child's day, the amount of time they spend outside in bright light is minimised.''
