Human eyesight is degrading right before our eyes, and the problem is growing
by Robert Roy Britt
Human eyeballs are growing longer, from front to back, at an alarming rate, resulting in a spike in the prevalence of myopia, or nearsightedness. Among Americans, rates of myopia have increased from 25% of people in 1971 to more than 40% today, according to the National Eye Institute. In the major cities of developed Asian countries, the rate exceeds 80% among students as they graduate from high school.
But researchers and eye doctors, many of whom view myopia as a growing epidemic, are largely mystified over the mechanisms behind it. Evidence points to two likely and related culprits during the critical years (infancy to late teens) when eyeballs grow and develop their ultimate shape:
- Increased time focused on smartphones, tablets, and other up-close tasks in school and during heavy homework loads.
- Lack of exposure to bright daylight, which is thought to offer a protective effect against myopia.
The severity of myopia is also increasing. An extreme form of nearsightedness, called high myopia, nearly doubled from 2.2% of the global population in 2000 to 4% in 2020. It’s projected to reach 10% by 2050, according to the World Health Organization. High myopia increases the risk later in life of glaucoma, which damages the optic nerve and is a leading cause of blindness in the elderly, as well as macular degeneration, which cracks and destroys the macula at the center of the retina, ruining straight-ahead vision.
“We may only know the full impact of myopia as the population ages,” Lisa Ostrin, a University of Houston optometrist who studies myopia in children, tells Elemental.
Barbara Caffery, president of the American Academy of Optometry, worries that not enough is being done to determine the problem’s causes and solutions. “We are witnessing an epidemic, one that will bring tragedy, morbidity, depression,” Caffery wrote last year in an open letter to colleagues. “Surely we will not be known as the myopic ones, the ones that missed the obvious.”
What is myopia?
Myopia develops when the eyeball grows into a pear shape instead of being round, or when the cornea becomes too curved, so that instead of focusing objects on the light-sensitive retina at the back of the eye, distant objects are focused in front of the retina. Close objects may be clear, but things in the distance are blurry.
Seemingly small differences have a huge effect. A normal adult eyeball measures about 24 millimeters (0.94 inches) front to back, explains Langis Michaud, a professor of optometry at the University of Montreal. There’s very little variation across the human species. But in the average myopic adult, it grows to 25 millimeters. Higher myopes, as they are called, can see this measurement exceed 26 millimeters. A typical toothpick, for comparison, is about two millimeters thick.
When he first started in optometry 35 years ago, Michaud would see the occasional nearsighted young person, typically with modest myopia at around age 13 that would stabilize to a moderate level by age 18.
“This was considered a benign myopic evolution, easily manageable with glasses, contact lenses, and, later on, laser surgery” when that procedure became possible, he says. Now, every week he sees children as young as seven whose myopia is as bad as the 18-year-olds from 35 years back. “If I do nothing, they will become highly myope and will face pathological consequences,” Michaud says.
The number of cases and the ongoing increase “qualifies the phenomenon as an epidemic,” Michaud says. He and other experts agree that while myopia can be inherited, genetics can’t explain the relatively recent spike in prevalence.
A normal adult eyeball measures about 24 millimeters front to back. There’s very little variation across the human species. But in the average myopic adult, it grows to 25 millimeters.
The irony of cause and effect
If diagnosed, myopia can be managed with specialized glasses or, preferably, with specialized contact lenses, which can stall the progression.
But kids with myopia may not realize their inability to see the blackboard is unusual, so they often struggle in school, frustrating themselves and their unknowing parents and teachers, according to a report from Education Week.
Only 40 U.S. states require vision screening for school-age children, and protocols vary by state. The American Optometric Association says school screenings fail to identify up to 75% of children with vision problems. Education Week’s analysis found that one in three U.S. schoolchildren haven’t had any vision screening in the past two years. Other research finds only 40% of kids age five and younger have had a vision test of any kind.
There’s a great irony to all this. While myopia can make it hard for a child to read a faraway blackboard, increased time spent in class or doing homework, focusing on books or screens and other up-close tasks, appears to be contributing to myopia, research suggests.
But the research has not proven conclusively whether perhaps myopic children are more likely to spend more years in school, or if more years in school and “something about the way we educated our children [is] causing the increasing prevalence of myopia,” says Denize Atan of the University of Bristol Eye Hospital in England.
In a 2018 study in the British medical journal BMJ, Atan and colleagues found that every single additional year of education is associated with increased nearsightedness; they conversely found little evidence suggesting myopia caused people to remain longer in school. She says her research provides the strongest evidence yet that something about time spent in education is contributing to nearsightedness.
It’s not a leap for researchers to suggest what’s going on: Educators increasingly rely on technologies like tablet computers and less on blackboards and the overhead projectors of days gone by. And today’s kids are asked to do more homework than in decades past, again often involving small screens and other close-up work.
Close work strains the eyes to converge and focus, Michaud says. Close-up screens “generate a visual demand that the visual system of the young kids cannot handle,” he says, adding that the effort can trigger eye fatigue, dryness, redness, double vision, and loss of concentration.