“We were meant to be outdoor creatures”: Experts say screens are only part of poor vision epidemic

It has long been thought that digging your nose in a book and spending too much time reading things up close could cause near-sightedness. When books were replaced with smartphones, it was easy to blame the screens instead. But as near-sightedness rates continued to rise across the world, researchers began to understand that it wasn’t just technology that was changing the way we see the world.

Near-sightedness, formally known as myopia, occurs when the eye elongates, causing light to focus in front of the retina instead of directly on it, producing blurry vision. Rates of myopia are increasing globally, with the World Health Organization estimating that half of the world’s population could have myopia by 2050 in what is already being called an epidemic. As of 2010, just 27% of the global population has myopia.

In addition to needing glasses or corrective lenses, people with myopia are at a higher risk of experiencing a detached retina if the retina has to stretch too far to accommodate the elongating eye. It also carries an increased risk for glaucoma, cataracts and myopic maculopathy, in which the center of the retina deteriorates. Poor vision can also have downstream effects on language, memory, and attention as we age.

Although genetics play an important role in determining whether someone will develop myopia, the increasing prevalence is happening too quickly for genetics to be the sole cause — meaning the rise of near-sightedness must also be caused by something in the environment, said Dr. Katherine Weise, a pediatric optometrist at the University of Alabama at Birmingham.

“There are environmental factors that seem to be contributing to this,” Weise told Salon in a phone interview. “So if we can figure out those environmental factors, we can mitigate the growth of myopia by reducing them.”

In the U.S., 25% of the population was near-sighted in the 1970s, and that rose to 41% in the early 2000s, according to data from the National Health and Nutrition Examination Survey. Although there is not more recent comprehensive federal data in the U.S. to compare trends, studies from around the world indicate that those rates have continued to rise, with China reporting a steady increase in myopia over the past decade. In Taiwan, up to 90% of young people have myopia.

Because electronic devices were not widespread when myopia started to increase, it is thought that the myopia epidemic could be caused by children spending less time outside, where a wide range of wavelengths of light can interact with their eyes and promote healthy growth, said Dr. Safal Khanal, an optometrist and researcher at the University of Alabama at Birmingham.

“It seems like the mechanism that is controlling the growth of the eye requires feedback from a very broad range of wavelengths,” Khanal told Salon in a phone interview. “If somehow that feedback is broken, for example, if kids are exposed to only a certain kind of wavelength, then that can mess up your refractive development.”

In one 2021 study published in JAMA Ophthalmology, children’s vision significantly declined toward myopia during school closures in 2020 — when children were at home and on screens more — compared to the rate at which their vision was changing in prior years. 

But time indoors and spending time on devices have been difficult to tease apart in research, and it could also be that technology is playing a role in the increased rates of myopia. In one recent animal study, tree shrews were made to look at a digital device. Through manipulating the red, green and blue color wavelengths on the screen, the researchers were able to control the growth of the eye.

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“There is some indication that chromatic composition of light, whether it is outdoors or from digital devices, is an important factor in this whole mechanism,” Khanal said.

In one 2010 study that followed a group of children through adulthood, children had a 60% of becoming myopic by eighth grade if they had low levels of outdoor activity. If they played outside for more than 14 hours, their risk of near-sightedness dropped to 20%.

However, reading and doing other close-up activities in what is referred to as “near-work,” was not associated with near-sightedness, said study author Dr. Donald Mutti, an optometrist and researcher at the Ohio State University College of Optometry.

“This has been replicated around the world: time outdoors, before a child becomes myopic, helps either prevent or delay the onset of their myopia,” Mutti told Salon in a phone interview. “In my mind, the biggest change that's been detrimental has been that kids don't spend as much time outdoors as they used to.”

However, Mutti said more research is needed to study the impacts of screen time in very young children and myopia risk. When infants are born, their eyes are not developed to focus on close-up objects well, and this naturally improves as the eye grows. The idea is that such early exposure to screens could potentially push that corrective adaptation too far into near-sightedness territory and influence the risk of myopia.

“Toddlers were meant to use their focusing power to get over their far-sightedness and then be toddlers … not read books or stare into screens,” Mutti said. “Then they learn to read and the ordinary near-work starts, but the eye is, for the vast majority, already grown to its adult size.”

As near-sightedness continues to increase around the world, efforts are being made to recognize it as a disease, which could improve surveillance and treatment. As it stands, insurance companies do not cover the medical aspects of myopia, Weise said. Last year, the WHO launched an initiative aiming to increase the proportion of people with access to glasses by 40% across the world. The National Eye Institute also hosted a meeting last year to better understand the epidemic and get it under control.

“The great thing about it being environmental factors contributing to the eye condition is, once we figure out what the factors are, we can use the factors to undo it as well,” Weise said.

Still, it seems that technology and urbanization are rapidly outpacing efforts to curb the myopia epidemic, with people spending more and more time inside on their devices. For now, perhaps we can take a page from countries like Australia, which has a relatively low rate of myopia — and where inhabitants also spend lots of time outdoors.

“We weren’t supposed to spend our days in a cave — we were meant to roam and be hunters and gatherers and be under the sun,” Mutti said. “We were meant to be outdoor creatures.”