Half of the world’s population could be short-sighted by 2050, research shows. That's an increase of more than a third on today's number. The reason why? According to researchers, our addiction to smartphones and tablets is playing a major role.

Examining global incidences of myopia over a 20-year period between 1995 and 2015, US researchers used the data to project the prevalence of the condition in the coming decades.

It is predicted that 4.8 billion people - or 49.8% of the world’s population - will require glasses by 2050.

The study, published in Ophthalmology, found myopia likely to be more prevalent in developed economies.

The problem is most acute in East Asia, South East Asia and Asia-Pacific, where by 2050 around two thirds of the populations of these regions will be short-sighted.

Not far behind were North America, with 58.4%, Western Europe with 56.2% and Australasia with 55.1%.

Screen time

While the research acknowledges that there is some genetic predisposition to short-sightedness, it claims that genetics alone cannot explain myopia’s upward trend.

Instead, the study claims that the increase is driven by lifestyle changes such as “the excessive use of near electronic devices”.

And the study’s findings on regional myopia rates seem to correlate with data on smartphone ownership.

Image: Pew Research Center

As the map above illustrates, many of the countries with the highest levels of smartphone ownership – such as South Korea and Australia – fall within the regions likely to have the highest levels of short-sightedness in the coming decades.

Step outside

However, while there’s a correlation between increased use of screens and increased prevalence of myopia, it is unlikely that screens on their own are the problem.

The Ophthalmology study blames the increase in short-sightedness on “a combination of decreased time outdoors and increased near work activities”.

Other research shows that rather than screens themselves, it is a lack of sunlight that is causing the problem.

A study of 4,500 US children over 20 years by Ohio State University found no relationship between short-sightedness and time spent reading or closely staring at a screen.

However, it was found that children who spent more time outdoors were less likely to suffer from myopia.

Similarly, an Australian study of more than 4,000 children at Sydney primary and secondary schools for three years found that children who spent less time outside were at greater risk of developing myopia.

Image: Ian Morgan, Australian Natl Uni

It is not yet known exactly why time spent outdoors is so important in preventing the condition.

However, Ian Morgan of the Australian National University in Canberra has studied rates of short-sightedness across Asia and Australia, and claims it comes down to the way that light (or lack of it) affects development of the eyeball.

As early as a decade ago, Morgan was claiming that exposure to sunlight cuts myopia rates by encouraging the release of dopamine.

Dopamine is known to inhibit eye growth and myopia is a condition caused by excessive eye growth.

Subsequent studies seem to have borne out his theory: in one study of schools of Guangzhou, China, Morgan and his team found that schools where pupils spent more time outside had a 23% lower incidence of myopia.