Youngsters team up to construct houses in the Wiki Tribe theme park in Huzhou, Zhejiang province. (Photo: China Daily)

Schools that have resumed classes should hold at least two hours of outdoor activities to prevent or control myopia, Wang Bin, a senior official with the National Health Commission, said at a news conference on Sunday.

Wang said the eyesight of many children might have been affected since they stayed at home for such a long time because of the Covid-19 outbreak.

Exposure to sun can prevent children from becoming shortsighted, she said, adding more outdoor activities are needed to keep eyesight of those with myopia from deteriorating.

"Schools that have resumed classes should let students out of classroom during physical education classes and 30-minute breaks. Given the outbreak, children should maintain safe distance," she said.

Wang added that schools that have access to qualified medical institutions should operate vision screening for their students.