Researchers examined data from 45 studies with more than 335,000 participants who were 9 years old on average. Participants either had eye exams or reported whether they were nearsighted. They also shared information about how many hours a day they spent using devices like smartphones, tablets, computers, or gaming consoles.
Overall, each extra hour of daily screen time was associated with a 21 percent higher risk of developing myopia, or nearsightedness, according to findings published in JAMA Network Open. And once people became nearsighted, screen time was tied to 54 percent higher odds that their myopia would get worse.
“There is an epidemic of myopia across the globe,” says Rahul Khurana, MD, a retina specialist at Northern California Retina Vitreous Associates, in Mountain View, and an associate clinical professor in ophthalmology at the University of California in San Francisco.
“Major contributors to this are increased near vision activities and reduced outdoor time,” says Dr. Khurana, who wasn’t involved in the new study. “Increasing smartphone use and near work with them is likely also contributing to this.”
Smartphones May Be Driving Higher Rates of Nearsightedness
Many of the studies included in the new analysis focused specifically on smartphones, although several also examined the impact on vision of other types of screen time, like playing video games, using a tablet, or working at a computer.
There doesn’t appear to be a meaningful connection between vision issues and less than an hour of daily screen time, according to the new study findings.
However, people who spent one hour a day on screens were 5 percent more likely to develop myopia than those with less daily screen time, the study found. And people with at least four hours of daily screen time were twice as likely to be nearsighted than individuals with less screen time.
The study wasn’t designed to prove whether or how screen time might directly cause vision problems. One limitation of the analysis is that it focused primarily on school age children and adolescents, a population that may not necessarily have the same digital habits as older teens or adults.
Television Time May Not Be as Risky
Another drawback of the study is that it doesn’t distinguish between different types of screens — such as smartphones that require focusing a short distance and televisions or gaming consoles that might be viewed from across a room, says Ian Morgan, PhD, a visiting fellow at Australian National University and a visiting professor at the Zhongshan Ophthalmic Center at Sun Yat-Sen University in Guangzhou, China.
“Previous studies have suggested that television use is not a risk factor for myopia,” says Dr. Morgan, who wasn’t involved in the new study. “This may be because viewing distances are generally longer — commonly around 2 meters [about 6 feet] or more.”
Higher Rates of Myopia Among Millennials
Two waves of technology — the arrival of the internet in the 1990s and the advent of smartphones in the 2000s — were both followed by surges in myopia as people dramatically increased how much time they spent looking close up at screens, Morgan says. Exacerbating vision problems, many people spent less time outdoors as they ramped up their use of computers and smartphones, Morgan adds.
“I suspect screen time that requires very close distance, like reading books or looking at smartphones puts you at highest risk,” Khurana says. “Previous studies have conclusively shown that near vision activities like reading books increase the risk of myopia, and I agree that smartphone use is in this category.”
There’s a pretty simple way to counter the risk of nearsightedness associated with screen time, however.
“Minimize near vision activities that are not necessary and maximize outdoor time,” Khurana says.
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