Weekend Long Reads: The Eyes Have It

by Kevin Schofield

This weekend's long read is a journey into "things that doctors knew but never bothered to tell us." And specifically about our eyes.

For the last several years the worldwide medical community has become increasingly concerned about an increase in nearsightedness, or "myopia" in the medical parlance. The World Health Organization estimates that over half of the world may be nearsighted by the year 2050. Nowhere has this raised more concern than China, where in some cities myopia has already become nearly universal among children. Chinese medical researchers have led the inquiries into this phenomenon, and they have come to the conclusion that the main cause of myopia in children is lack of regular exposure to sunlight. Many of the Chinese cities with the highest rates of myopia in children are also the cities with the worst air pollution, and children largely stay inside. Researchers acknowledge that genetics is probably also a factor, and an increase in intensity and duration of "near work" such as using phone and tablet screens is another contributor, but there is overwhelming evidence that kids need exposure to sunlight in order for their eyeballs to grow into the right shape and to let the optics work correctly.

In one Chinese city, Feicheng, public health researchers have been conducting a long-term study of children ages 6 through 13, testing them each year to try to learn more about the progression of childhood myopia. They have accumulated a wealth of data, and from 2015 through 2019 the percentage of nearsighted children at each age was consistent — starting at about 5% of children at age 6 and increasing to around 80% of them by age 13.

And then COVID-19 happened, and the city locked down for the first half of 2020. When the myopia researchers did their annual data collection last June, they discovered that some of the numbers had shifted substantially — in particular for the kids at the lower end of the age range in the study. The percentage of myopic 6-years-old nearly quadrupled, from 5.7% in 2019 to 21.5% in 2020. It doubled for 7-year-olds, and increased by 41% and 17% respectively for 8- and 9-year olds. But for kids 10 and older, there was no significant change from previous years.

We can learn a couple of important lessons from this. First, this provides even more evidence that lack of sunlight is a major contributor to childhood nearsightedness. Second, and perhaps more important, it tells us that ages 6 to 8 probably are the key years in which kids' eyeballs grow into their proper shape and are the time when it's most critical that kids spend time outside.

There is much we still don't know about this. It's possible, though perhaps unlikely, that this dramatic increase in nearsightedness for Feicheng's kids in 2020 will correct itself at least partially in the next couple of years as life goes back to normal there. We also don't know what it means for children aged 5 and younger, since the researchers haven't been collecting data on them.

But it's also very likely that this isn't confined to one city in China, and the COVID lockdowns that happened around the world — and are still happening intermittently in some hotspots — will lead to a worldwide spike in myopia in children.

But the immediate takeaway is clear: Make sure your kids get plenty of time outside, especially those in elementary and middle school. Do it safely during COVID, and make sure they wear masks and wash their hands frequently if they will be around other people, but it's critical for their eyesight that they get regular exposure to sunlight.

This is only one of many things that we've learned in recent years about how our environment affects our eyes, and ultimately our health. We also know now that there are receptors in the back of our eyes that regulate our body clocks and our sleep cycles. Because of this, doctors now recommend that the best therapy for overcoming jet lag is to go for a walk outside during the day because of the natural signals it sends through our eyes to our bodies. Even if you don't travel, getting outside every day helps keep your body clock in sync and lets you sleep better at night.

In a more worrisome finding, doctors studying astronauts have found that microgravity environments affect our vision: even just two weeks in space on a space shuttle caused some astronauts' vision to start to blur, and 60% of those on long-duration missions to the International Space Station have reported vision impairment. Researchers' best understanding of the phenomenon is that without the presence of gravity, fluid begins to pool behind our eyeballs, and the pressure it exerts flattens the back of the eye and distorts the optical distances between parts of the eye. The longer a person spends in space, the worse the problem seems to become. That suggests that flights to Mars are a risky proposition: after eighteen months in space, space travelers might arrive at the red planet essentially blind. At a minimum, crews for long space flights will need to have an optometrist on board with test equipment and the ability to manufacture corrective lenses. But it probably means that creating artificial gravity of some form, such as a section of the spacecraft that spins constantly and uses centrifugal force to push everything to the outer wall, will be essential for any long mission.

Progression of Myopia in School-aged Children after COVID-19 Home Confinement

Kevin Schofield is a freelance writer and the founder of Seattle City Council Insight, a website providing independent news and analysis of the Seattle City Council and City Hall. He also co-hosts the "Seattle News, Views and Brews" podcast with Brian Callanan, and appears from time to time on Converge Media and KUOW's Week in Review.

The featured image is attributed to Yogesh Moorhjani under a Creative Commons 2.0 license.