NEARSIGHTEDNESS IS AT EPIDEMIC LEVELS – AND THE PROBLEM BEGINS IN CHILDHOOD
Nearsightedness Is at Epidemic Levels – and the Problem Begins in Childhood
April 24th, 16PM April 24th, 16PM(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.)
Andrew Herbert,
Rochester Institute of Technology
(THE CONVERSATION) Myopia, or the need for corrected vision to focus or see objects at a distance, has become a lot more common in recent decades.
Some even consider myopia, also known as nearsightedness, an epidemic.
Optometry researchers estimate that
about half of the global populationwill need corrective lenses to offset myopia by 2050 if current rates continue – up from 23% in 2000 and
less than 10% in some countries.
The associated health care costs are huge. In the United States alone, spending on corrective lenses, eye tests and related expenses
may be as high as US$7.2 billion a year.
What explains the rapid growth in myopia?
I'm a vision scientistwho has studied visual perception and perceptual defects. To answer that question, first let's examine what causes myopia – and what reduces it.
How myopia develops
While having two myopic parents does mean you're more likely to be nearsighted,
there's no single myopia gene. That means the causes of myopia are more behavioral than genetic.
Optometrists have learned a great deal about the progression of myopia by
studying visual development in infant chickens. They do so by putting little helmets on baby chickens. Lenses on the face of the helmet cover the chicks' eyes and are adjusted to affect how much they see.
Just like in humans, if visual input is distorted, a chick's eyes grow too large,
resulting in myopia. And it's progressive. Blur leads to eye growth, which causes more blur, which makes the eye grow even larger, and so on.
Two recent studies featuring extensive surveys of children and their parents provide strong support for the idea that an
important driver of the uptickin myopia is that
people are spending more timefocusing on objects immediately in front of our eyes, whether a screen, a book or a drawing pad. The more time we spend focusing on something within arm's length of our faces, dubbed "near work," the greater the odds of having myopia.
So as much as
people might blame new technologies like smartphonesand too much "screen time" for hurting our eyes, the truth is even activities as valuable as reading a good book can affect your eyesight.
Outside light keeps myopia at bay
Other research has shown that this unnatural eye growth can be interrupted by sunlight.
A 2022 study, for example, found that myopia rates
were more than four times greaterfor children who didn't spend much time outdoors – say, once or twice a week – compared with those who were outside daily. At the same time, kids who spent more than three hours a day while not at school reading or looking at a screen close-up were four times more likely to have myopia than those who spent an hour or less doing so.
In another paper, from 2012, researchers
conducted a meta-analysis of seven studiesthat compared duration of time spent outdoors with myopia incidence. They also found that more time spent outdoors was associated with lower myopia incidence and progression. The odds of developing myopia dropped by 2% for each hour spent outside per week.
Other researchers have reported similar effects and argued for
much more time outdoorsand changes in early-age schooling to reduce myopia prevalence.
What's driving the epidemic
That still doesn't explain why it's on the rise so rapidly.
Globally, a
big part of this is due to the rapid developmentand industrialization of countries in East Asia over the last 50 years. Around that time, young people began spending more time in classrooms reading and focusing on other objects very close to their eyes and less time outdoors.
This is also what researchers
observed in the North American Arcticafter World War II, when schooling was mandated for Indigenous people. Myopia rates for Inuit went from the single digits before the 1950s to upwards of 70% by the 1970s as all children began attending schools for the first time.
Countries in Western Europe,
North Americaand Australia have shown
increased rates of myopiain recent years but nothing approaching what has been observed recently in
China, Japan, Singapore and a few other East Asian countries. The two main factors identified as leading to increased myopia are
increased readingand other activities that require focusing on an object close to one's eyes and a
reduction in time spent outdoors.
The surge in myopia cases will likely have its worst effects 40 or 50 years from now because
it takes timefor the young people being diagnosed with nearsightedness now to experience the most severe vision problems.
Treating myopia
Fortunately, just a few minutes a day with glasses or contact lenses that correct for blur
stops the progression of myopia, which is why early vision testing and vision correction are important to limit the development of myopia. Eye checks for children are mandatory in some countries,
such as the U.K.and
now China, as well as
most U.S. states.
People with with high myopia, however, have
increased risk of blindness and other severe eye problems, such as retinal detachment, in which the retina pulls away from the the back of the eye. The chances of myopia-related
macular degenerationincrease by
40% for each diopter of myopia. A diopter is a unit of measurement used in eye prescriptions.
But there appear to be two sure-fire ways to offset or delay these effects: Spend less time focusing on objects close to your face, like books and smartphones, and spend more time outside in the bright, natural light. Given the first one is difficult advice to take in our modern age, the next best thing is taking frequent breaks – or perhaps spend more time reading and scrolling outside in the sun.
This article is republished from The Conversation under a Creative Commons license. Read the original article here:
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