Researchers at the Chinese University of Hong Kong on Tuesday said parents and teachers have not been taking care of their children's eyesight, which has worsened during the pandemic.

The university surveyed about 19,000 primary and secondary students, and their parents and teachers, in June last year.

It found that more than half of the parents reported some deterioration in their children's eyesight, but few of them did anything about it.

Jason Yam, an associate professor at the university, said the worsening eyesight was a result of the children having too much screen time, but the situation is unlikely to improve even now face-to-face classes have resumed.

"Covid aggravates the situation. If we resume face-to-face learning, it is better than online learning. But the situation or the condition of myopia boom will not disappear for sure," he said.

"Parents are not fully aware that myopia can be potentially so serious that it can lead to sight-blinding complications in the future."

Researchers added that Hong Kong is among the cities with the highest prevalence of short-sightedness in the world.

They said students in higher grades are more likely to have vision complications, with 28 percent of primary three pupils affected by short-sightedness, and 66 percent of those in secondary three.

Another researcher, Clement Tham, said parents and teachers should encourage non-digital activities as they help suppress the progression of short-sightedness.

"They should encourage their children to do more outdoor daytime activities, aiming for at least two hours per day, or an accumulative of about 14 hours per week," Tham said.