More than 40% of Americans are estimated to have myopia, also known as nearsightedness.

While many may consider it a minor inconvenience easily remedied with glasses, authors of a report published Tuesday are calling on health agencies to classify it as a disease.

Committee members at the National Academies of Science, Engineering and Medicine say nearsightedness has become an "evolving epidemic" that requires more research, standardization of care and early prevention, recommending at least one hour of outdoor time daily for kids.

This is the first time the National Academies has published a report on myopia since 1989. Some research suggests myopia may have increased by 25% from 40 years ago in parts of the country, according to the American Optometric Association.

"It was long overdue," said Dr. Terri Young, committee co-chair and professor of ophthalmology and visual sciences at the University of Wisconsin-Madison.

Researchers aren't exactly sure why myopia is increasing so much, but think it may have to do with the amount of time children spend indoors on screens.

"In the U.S., it's rapidly increasing and we don't have a handle on it," Young said.

Myopia, or nearsightedness, is a vision condition where close objects look clear but far objects look blurry.

This occurs when the shape of the eye causes light rays to bend and focus in front of the retina instead of on it. The retina is a nerve at the back of the eye that converts light into electrical signals for the brain to process into an image, according to the Mayo Clinic.

The condition typically begins in childhood, said Dr. Fatema Ghasia, a pediatric ophthalmologist at Cleveland Clinic's Cole Eye Institute.

Babies are born farsighted, but vision typically corrects with growth. In kids with myopia, the eye grows too much, passing beyond the point of focusing the image.

Young, from the National Academies report, expects that trend to continue if the U.S. doesn't implement a concerted, national effort toward preventing and effectively diagnosing nearsightedness in children.

Myopia hasn't been considered an urgent issue up to this point, she said, but its potential impact on children should make it one. Research has shown poor vision decreases academic performance.

"It just has a downstream impact on how that child will function in society," she said.

The National Academies report said one of the best ways to prevent nearsightedness in kids is to spend time outdoors, at least one to two hours every day.

"There's something about being outside, looking at long distances, appreciating horizons (and) different wavelengths that somehow thwarts myopic development," Young said.

During days when it might be difficult to make it outside, experts said being near windows and doors with daylight streaming in can also help.

It doesn't have to be sunny outside, Ghasia said. What's important is that the child is exposed to natural light.

Outdoor time is not just the parents' responsibility, experts say. Schools and daycares should be making sure students get enough time outside. A 20-minute recess is not enough, the National Academies authors said.

While the gold standard is at least an hour of outdoor time, any time outside can potentially prevent the progression of myopia, said Ghasia.

Young said she's clocked a "myopic shift" among kids in her clinic.

This shift is twofold. One is that nearsightedness is being diagnosed at younger ages. Instead of finding myopia in children at ages 5 or 6, Young said it's becoming more common to diagnose myopia in children as young as 3 or 4.

Doctors are also seeing a change in what's considered normal eyesight. Whereas perfect vision used to be considered the baseline, Young said this has shifted so that most patients have at least mild myopia.

Eye doctors may be able to slow these trends - and maybe even reverse them - if patients were screened, diagnosed and treated early. However, the National Academies report said the lack of standardization in care hinders healthcare providers from intervening as early as possible.

For example, patients are not all screened at the same age. Although Young recommends children receive their first screening at a wellness visit before entering school, some patients aren't screened until second or third grade. Diagnostic tools are also not standardized; while some doctor's offices use eye drops during visual tests, others don't.

Diagnosing and addressing myopia early is important to ensure a child's development is on the right track, Ghasia said. Vision is not only tightly linked with academics but also with sports performance and social development. People who have myopia are also at increased risk of other ocular complications like retinal detachment and glaucoma later in life.

"Myopia is not just a nuisance," she said. "It has serious long-term ramifications."

Adrianna Rodriguez can be reached at [email protected].