More than one in three children and teenagers worldwide are shortsighted, according to the largest study of its kind, prompting calls to discourage screen time and increase physical activity. Shortsightedness, or myopia, is an eye condition where someone cannot see objects far away clearly. It is usually corrected with glasses or contact lenses.

Experts are unsure why it occurs but studies have shown that children who use computers or smart devices for long periods are at greater risk. Some say that spending more time outdoors can help. The most comprehensive global analysis to date reveals a dramatic increase in myopia over the last30 years, with the toll of myopia among children and teenagers set to top 740m cases by 2050.

Girls, and children or teenagers living in urban areas, are more likely to develop the condition, according to the analysis published in the British Journal of Ophthalmology . Myopia typically starts in early childhood and tends to worsen with age, according to the researchers led by Sun Yat-sen University in Guangzhou, China. The condition has emerged as a major public health concern, they added.

The most recent global review of its prevalence went up to 2015. To obtain a more up to date picture, to inform healthcare policy and preventive efforts, the researchers estimated the current and future prevalence of myopia up to 2050 among people aged between five and 19. They drew on all relevant research and government reports published to June 2023.

They inc.