There’s no way around it: Since the pandemic began, kids of all ages are spending lots more time looking at screens, particularly as many schools shifted from the classroom to the computer. A survey conducted by Ipsos and the Global Myopia Awareness Coalition found that 44 percent of U.S. children are using electronic devices for over four hours a day, more than double the rate before the pandemic.

Naturally, there are worries about the effects on physical activity, loneliness and sociological gaps. But in the United States, I think not enough people are considering another potential side effect of living through screens: eye damage.

Our eyes aren’t built to read on screens. Several aspects — such as viewing angles and screen glare — force our eyes to work harder than they do while studying a printed page. That strain, plus the extensive close-up work that online school requires, may lead to eye problems, some of which can last a lifetime.

As a scientist who has dedicated a lot of my career to studying the visual system and protecting the human eye, I am worried.

In the United States and other countries, monitoring eye health isn’t a major public health priority, particularly when in the grips of a pandemic. This isn’t the case in China, where I spend a lot of my time — there, eye health is more closely watched, particularly in children. And troubling trends are emerging: A January study of more than 120,000 children in China found that the rate of myopia (nearsightedness, or trouble seeing things at a distance) among children ages 6 to 8 increased markedly during a home confinement period, when schools closed from January through May because of covid-19, the disease caused by the coronavirus. Among 6-year-olds, the rate of myopia following lockdown was 21.5 percent; before covid-19, the highest yearly rate in that age group since 2015 was 5.7 percent.

These data aren’t surprising to me. Several aspects of screen reading make it taxing on our eyes. Although it’s unclear whether screen time itself is a risk factor for myopia, close-up work definitely is — and online school requires far more of this.

There also is the problem of viewing angles, since people may look at digital displays at unusual angles, such as while in bed, with a smartphone or laptop on their laps. The screen often offers less contrast between letters and the background than the printed page, and glare and reflections from the screen may also force the eyes to work harder. Reading on a screen can exacerbate existing eye problems, as eyeglass and contact lens prescriptions for page reading may not work as well.

I suspect that myopia rates are increasing in other countries that don’t monitor eye health as closely as China does. It’s a particular issue for elementary-school-aged children, whose eyes may be especially susceptible to developing myopia. Myopia is more than an inconvenience: It can be costly to correct (requiring regular eye exams and glasses or contact lenses), and people with severe nearsightedness are at higher risk for additional conditions such as retinal tears, cataracts and macular degeneration, which may threaten their eyesight altogether.

If uncorrected, myopia (or its cousin, farsightedness) can contribute to another eye problem directly related to screen time: computer vision syndrome, also known as digital eyestrain, marked by blurred vision, dry eyes and neck and shoulder pain. The more time you spend reading on a screen, the more at risk you are. Not surprisingly, the spike in screen time we have seen with covid-19 is accompanied by reports of more digital eyestrain around the world. One survey by researchers in India found that 50 percent of children taking online classes had digital eyestrain.

The good news: People can take easy steps to protect and heal their eyes. The 20-20-20 rule — looking at least 20 feet in the distance for 20 seconds every 20 minutes spent on the screen — is key, and should be included as part of the curriculum in online schooling. In China, the Education Ministry has said electronics can make up no more than 30 percent of teaching time, and students can’t spend more than 20 minutes each day on electronic homework.

But here is the best advice: Go outside.

An analysis of 27 studies suggests it is the combination of long screen time and less time outdoors that puts young children at greatest risk of myopia. One study of first-graders in China (average age of 6) found that those who were given 40 extra minutes of outdoor time at school were 9 percent less likely to develop myopia over the next three years.

Why? The outdoor environment provides bright and full-spectral light, rich spatial patterns across a wide range of scales, and sharp images of distant objects — all of which may protect the eyes from myopia.

So if you’re worried about the effect of covid-19 restrictions on children’s eyes, I say: Stop reading this, and send them outside.

Zhong-Lin Lu is chief scientist, associate provost for sciences and co-director of the NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, as well as professor of neural science and psychology and Global Network professor at NYU. This article was produced with Knowable Magazine, a journalistic publication covering science and its emerging frontiers.