Pandemic lockdowns may have damaged the eyesight of children, with young people nearly twice as likely to be short-sighted than before Covid, possibly because they spent less time outdoors and longer in front of a screen, researchers believe.

Scientists in Hong Kong found the estimated chance of developing myopia for a six-year-old rose from 17 per cent before the pandemic to 28 per cent.

Similarly for seven-year-olds, the risk increased from 16 per cent to 27 per cent and eight-year-olds from 15 per cent to 26 per cent.

Short-sightedness, or myopia, usually occurs when the eyes grow slightly too long, so that objects in the distance appear blurred.

Previous studies have found that playing outside as a child reduces the risk, which may be linked to light levels, or because being indoors increases the time spent gazing at near objects and not enough time looking across long distances.

Researchers from the Chinese University of Hong Kong studied 1,793 children and found that during the pandemic, they increased their screen time from 2.5 hours per day to about seven hours, while daily time spent outdoors reduced from one hour 15 minutes to roughly 24 minutes per day.

Children and young people’s activity levels

Densely populated Asian communities are particularly badly affected by myopia, but in Britain, the number of short-sighted children has doubled in the past 60 years, with 16 per cent of children now myopic by the time they reach the ages of 12 to 13, compared to seven per cent in the Sixties.

Children have been particularly badly affected by the pandemic, with schools closed in favour of online learning, while stay-at-home rules meant many children were unable to spend time outdoors.

Short-sightedness also put children at risk of developing complications that increase the risk of irreversible blindness later in life, the researchers said.

Although the study is observational, and so cannot definitely link the increased levels to the pandemic, the team said it had uncovered an “alarming” rise in myopia which needed to be addressed.

Dr Jason Yam, from the Chinese University of Hong Kong’s department of ophthalmology and visual sciences, said the data should “serve to warn eye care professionals, and also policy makers, educators and parents, that collective efforts are needed to prevent childhood myopia, a potential public health crisis as a result of Covid-19”.

How lockdown policies have impacted children

British experts said although it was hard to know whether the same results would apply in Britain, previous studies had shown that more time indoors did increase the risk.

Oliver Braddick, emeritus professor of psychology at the University of Oxford, said: “There is other evidence that outdoor activity in daylight has a protective effect against children developing myopia, which is consistent with the findings of this study.

“It should be noted that this study was carried out in an urbanised east Asian population, among whom myopia levels are generally higher than in groups of European ancestry. 

“It remains unclear whether there is any genetic component to this difference, or whether it is a result of cultural factors.”

The results were published in the British Journal of Ophthalmology.