Children on mobile phones – “epidemic of myopia”

The dose makes the poison – this also applies to the connection between screen time and myopia. According to Norbert Pfeiffer, Director of the Department of Ophthalmology at the University Medical Center Mainz, the risk hardly increases up to about one hour per day, citing a recently presented review study. According to this study, each additional hour represents a significant increase in risk of about 20 percent.

From about five hours of screen time onward, the curve flattens, and the risk of becoming myopic appears to increase only gradually. Time spent on smartphones, tablets, game consoles, computers, and televisions was included.

With nearsightedness, also known as myopia, distant objects are perceived as blurry. While life expectancy and fitness among older people are increasing in many countries, the eyesight of entire societies has deteriorated at an almost unbelievable rate in recent decades. And with the proliferation of smartphones, the wave of myopia threatens to become even higher, warns Pfeiffer, board member of the Eye Foundation.

The analysis, presented in the journal "Jama Network Open," included 45 studies from recent years with a total of more than 330,000 participants of various ages. The authors caution that other near-vision activities such as reading or writing—which also contribute to myopia risk—were not taken into account. In many Asian regions, the number of nearsighted people was already high before the widespread use of digital devices.

To reduce the risk of myopia, all close-up work activities should probably be minimized, explains the team led by Young Kook Kim from the National University College of Medicine in Seoul. According to Pfeiffer, the distance from the eye is crucial. And here, too, there is a dose-response relationship: "Every centimeter closer increases the risk more."

Therefore, it's likely that the time spent in front of the tiny screens of smartphones, which are often held 20 centimeters or closer to the eyes, has by far the greatest impact. "With books, it's usually closer to 30 or 40 centimeters—and many children hardly read books anymore." The television, which is usually several meters away, probably doesn't pose a major problem, and the distance for computer screens is also comparatively large at around 60 centimeters.

This development becomes even more compelling when you consider how much childhood has changed and continues to change: Years ago, children wouldn't spend extended periods of time burying their noses in books until they were around seven years old, once they could read fluently. Today, in everyday situations—on the bus or while being pushed around in a stroller—you can see two- to three-year-olds staring spellbound at their smartphones, kept still by endless loops of animated films. "The earlier the eye begins to adapt, the greater the effect in the end," says Pfeiffer. "We're facing an epidemic of myopia," he fears.

Screen time is increasing rapidly, even among young children, experts from the Organization for Economic Cooperation and Development (OECD) recently warned. According to the study, seven- to twelve-year-olds in France, for example, already spend more than two hours a day in front of screens. In Germany, more than half of ten-year-olds own their own smartphone; by the age of 15, almost all have a device and average almost seven hours of screen time per day.

There are no figures on how many young people in this country are now short-sighted, says Mainz-based ophthalmologist Pfeiffer. "I wouldn't be surprised if it were already around 40 percent among 10-year-olds." In South Korea, studies of recruits show that over 96 percent, or almost all of them, are short-sighted. Similar data exist from China and Taiwan. In general, the problem is greater in Asian countries – partly because of the often significantly longer daily study hours.

"Our visual system is designed for long-distance vision," explains Pfeiffer. For tens of thousands of years, humans primarily used it to scan for threats and prey. The eye only had to strain when viewing something up close. Evolution simply wasn't prepared for us all to suddenly become couch potatoes and stare at tiny screens for hours on end.

"Near vision begins at about five meters," says Pfeiffer. The closer the object, the more the so-called ciliary muscle contracts, and the shape of the elastic lens changes. This keeps the image on the retina sharp even at close range. However, constant close vision leads to an adaptive response with which the eye reduces the energy-intensive muscle work: The eyeball grows longer, and the focal point of the eye is consequently in front of the retina. Near objects are therefore seen clearly with less muscle work, but distant objects appear blurry.

What seems like a mistake is actually just evidence of the enormous adaptability of this high-performance organ. "It's actually a perfectly reasonable process," Pfeiffer emphasizes. "Similar to the formation of calluses on heavily stressed body parts."

However, there is one major caveat: eye diseases such as cataracts, glaucoma, which can potentially lead to blindness, retinal detachment, and macular degeneration are more common in nearsighted people and likely develop earlier. "Furthermore, the risk of accidents is increased." Here, too, a clear dose-response relationship applies, as the physician explains: The more nearsighted someone is, the greater the risks.

The crux of the matter is: Myopia cannot be reversed. Glasses or contact lenses only correct existing refractive errors, but do not influence their further development, as Pfeiffer explains. And there are no easily administered miracle cures. Atropine drops – widely used in Asia – may temporarily reduce myopia, but they have severe side effects and make it harder for children to see and read in bright light. Similar problems exist with special lenses.

Parents therefore have every reason to prevent their children from spending long periods on their smartphones, especially considering their children's lifelong vision, emphasizes the Mainz expert. Ideally, they should send them outside – because there is a completely natural miracle cure for myopia: as much outdoor time as possible. Studies have repeatedly shown that children are less likely to become myopic when they spend a lot of time outdoors.

The exact reason for this isn't entirely clear, says Pfeiffer. Bright light inhibits eye growth, probably via the neurotransmitter dopamine, as analyses have shown. Another likely factor is that people look at things more than five meters away outside – and, not least, exercise itself, which also has a positive effect on several other areas of the body. "At least two hours of outdoor time a day will definitely slow the development of myopia," says Pfeiffer.

This effect helps explain why Asia, in particular, is so severely affected by myopia. Many people in Singapore, for example, only manage two hours outdoors per week at most, because almost all of their daily and leisure activities take place indoors. In Germany, the situation is different, at least for young children, thanks in part to the high value placed on playgrounds. But even in this age group, media time is increasing.

According to the authors of the review, nearly half of the world's population could be myopic by 2050. This increase is associated with earlier onset, faster progression, and more severe myopia. Furthermore, an increase in myopia-related, sight-threatening diseases is expected.

"We should listen more to what our grandmothers always said," advises Pfeiffer: Children need fresh air. "This also reduces the risk of obesity and the resulting illnesses, and the child has more social contacts." The recommendation to put down the cell phone more often and get outside for lifelong good eyesight doesn't just apply to children. Because, says Pfeiffer: "Eye growth doesn't finish until around the age of 25."