Young people spending hours staring at screens means half the world may need glasses within 30 years.
Phone devices and computer screens are to blame for the rising risk of short-sightedness among children and young adults, say scientists.
Researchers have found high levels of looking at a phone or tablet is linked with around a 30 percent higher risk of short-sightedness, also known as myopia.
But when it is combined with excessive computer use, that risk rose to around 80 percent.
Researchers fear that this could mean that by 2050, half the world or five billion people could be short-sighted.
The authors examined more than 3,000 studies investigating smart device exposure and myopia in children and young adults aged1 between three months old and 33 years old.
In 2019, the World Health Organization recommended children under two should not have any screen time and children aged two to five should have no more than one hour a day of sedentary screen time.
But in the same year, a CensusWide survey of 2,000 British families found children were spending an average of 23 hours a week staring at screens.
Numerous studies have also suggested that number has vastly increased during the Covid-19 pandemic.
Professor Bourne of Ophthalmology in the Vision and Eye Research Institute at Anglia Ruskin University said: "Around half the global population is expected to have myopia by 2050, so it is a health concern that is escalating2 quickly.
"Our study is the most comprehensive yet on this issue and shows a potential link between screen time and myopia in young people.
"This research comes at a time when our children have been spending more time than ever looking at screens for long periods, due to school closures, and it is clear that urgent research is needed to further understand how exposure to digital devices can affect our eyes and vision.
The study was published in The Lancet Digital Health.