BERKELEY, CALIF. — Lilith Sadil, 12, climbs into an examination chair here at the Myopia Control Center at the University of California. “Do you know why you are here?” asks Dr. Maria Liu, an optometrist.
“Because my eyes are changing fast,” Lilith says.
“Do you read a lot?” Dr. Liu asks.
“Do you use the computer a lot?”
Lilith is an active child who practices taekwondo. But like an increasing number of children, she has myopia — she can see close up but not farther away.
Her mother, Jinnie Sadil, has brought her to the center because she has heard about a new treatment that could help. Eye specialists are offering young patients special contact lenses worn overnight that correct vision for the next day.
Myopia has become something of a minor epidemic: More than 40 percent of Americans are nearsighted, a 16 percent increase since the 1970s. People with so-called high myopia — generally, blurry vision beyond about five inches — face an increased likelihood of developing cataracts and glaucoma, are at higher risk for retinal detachments that can result in blindness.
Exactly what is causing the nationwide rise in nearsightedness is not known.
“It can’t be entirely genetic, because genes don’t change that fast,” said Susan Vitale, an epidemiologist at the National Institutes of Health who studies myopia. “It’s probably something that’s environmental, or a combination of genetic and environmental factors.”
Some research indicates that “near work” — reading, computer work, playing video games, and using tablets and smartphones — is contributing to the increase. A recent study found that the more educated a person is, the more likely he or she will be nearsighted.
A number of other studies show that children who spend time outdoors are less likely to develop high myopia. But no one is certain whether the eye benefits from ultraviolet light or whether time outside simply means time away from near work.
Beyond corrective eyeglasses and contact lenses, there has been little parents can do for nearsighted children. Now optometrists like Dr. Liu are offering a treatment called orthokeratology — ortho-k, for short.
Myopia occurs when the eyeball elongates. Ortho-k contact lenses apply pressure to the cornea, flattening it. After wearing the lenses all night, patients have clear vision that lasts for one full day, after which the cornea returns to its natural shape.
The lenses have been around since the 1940s but caught on only recently in the United States, partly because of long-term clinical trials demonstrating that they may slow down the progression of myopia. A 2012 randomized clinical trial in Hong Kong, for instance, followed children for two years and found that the rate of growth of the eyeball in those wearing ortho-k lenses was 43 percent less than those who wore glasses.
Ortho-k is not just for children: adults can wear the lenses too, but the long-term benefits are limited. Because myopia tends not to progress after patients reach their early 20s, the lenses are not really preventive, Dr. Liu said.
“The studies do show that it seems to slow the progression, but it’s not a slam dunk,” said Dr. David Hunter, an ophthalmologist at Harvard University and Boston Children’s Hospital. “Especially in young children, where the risk of infection is high.”
Young patients may not be diligent about cleaning lenses properly and regularly to prevent bacteria growth, he said. One recent report in the journal Clinical and Experimental Ophthalmology found that infections from ortho-k lenses led to corneal scarring and permanent vision loss in four children in Australia.
Dr. Hunter does not prescribe ortho-k lenses to his patients. As an alternative, he sometimes prescribes atropine drops, which also have been shown to slow myopia’s progression in children. But there is reason to be wary of the drops too: They can cause loss of near vision and light sensitivity, requiring patients to wear sunglasses when outdoors.
Perhaps most important, Dr. Hunter said there was no research that tracked children long enough to show that either ortho-k lenses or the drops significantly reduce the severity of myopia by adulthood. Patients who use the lenses and drops may end up just as myopic as adults who do not, he said.
“I’m not convinced that it’s enough of a difference,” he said. “And generally, the idea that you’re putting these in to squish the corneas at night is not something I’m comfortable with.”
Dr. Hunter and other clinicians said that the best and easiest step a concerned parent could take was to reduce children’s time in front of computer, phone and television screens — and to send them outside to play.
Back in the center, Dr. Liu’s assistant does a few tests on Lilith and determines that her corneas are fairly steep, making her a good candidate for ortho-k.
Dr. Liu tells Mrs. Sadil it will cost about $1,000 to fit the lenses and $250 to buy a pair that will last a year. Mrs. Sadil decides to begin in January.
She wears thick glasses herself. “I would have done anything to not be so nearsighted,” she said.