These days, there’s nothing most kids like better than hanging out in the family room playing video games, sitting in front of the computer, texting with friends, or playing with their iPods.
Over the last several decades, myopia (or nearsightedness) has become an international problem.
Could there be a link between the two phenomena?
Researchers around the world have been studying the problem for several years now, but some of the causes – and fixes – may be starting to come into focus.
Bryan James Schwent, M.D., an ophthalmologist at the Retina Institute of Virginia, reports that the increase in myopia cases is rapid and alarming. According to a 2009 article in the Archive of Ophthalmology, the rate of nearsightedness in the United States has increased from about 25 percent to 42 percent in 12- to 54-year-olds over the last forty years or so. Research shows that the triggers likely occur in childhood, when the eye is growing and elongating.
“It’s a complicated issue,” Dr. Schwent notes. “As society changes, habits and behaviors change. It can become a matter of trying to tease out which comes first, the chicken or the egg. We will probably find that the factors are all interwoven, but finding a treatable cause is becoming more and more important.”
Tami Flowers, M.D., an ophthalmologist at Commonwealth Eye Care Associates, reports that the problem is even worse in Asia, with myopia rates approaching 80 percent in college age students in Singapore.
“This is obviously a problem,” she says.
“Nearsightedness may cause complications later in life. It’s not only the need for glasses, contacts or refractive surgery but moderate and high myopia can lead to vision-threatening ocular conditions.”
Dr. Flowers explains that myopes – people who are nearsighted – have an increased risk for retinal detachment which can result in severe vision loss.They also have a higher prevalence of cataracts, loss of the lens transparency resulting in reduced vision, as well as an increased risk for glaucoma, a disease that damages the optic nerve and can result in blindness.
“These are serious problems which make research all the more critical,” she emphasizes.
In myopes, the eyeball is longer than normal, the retina is further away from the focal point, and the lens is simply not able to move the focal point far enough back (Fig.1). Eyeglasses or refractive surgery are required to focus the object on the retina.
The next question, of course, is how does the eyeball get so unusually long? “The truth is that we don’t know for sure,” says Dr. Schwent “but there are lots of interesting theories.”
He notes that kids with parents who are nearsighted have a greater chance of being nearsighted themselves, and some ethnic groups, like Asian populations, have a higher risk. But studies show that heredity alone can’t come close to explaining why there is so much more myopia now, and why it is increasing so rapidly.
There may be a link with a lot of reading, computer use, or video games, but the data is not consistent. It’s been noted that the increase in nearsightedness has matched the increase in time spent on these activities, particularly in children, but other research shows that this isn’t enough to explain the changes.
The answer is still a big area of research, but new data might supply some answers. Kathryn Rose, Ph.D., associate professor at the University of Sydney, Australia, recently published a study in the American Academy of Ophthalmology’s journal showing that kids who don’t spend much time outside in sunlight are more likely to develop myopia.
Noting that Dr. Rose’s study followed more than 2,000 kids for five years, Dr. Schwent says its findings are well-supported.”If it’s not inborn, it must be caused by external factors, but until this report, there were few consistent hints about what these factors could have been,” says Dr. Schwent. “This is strong data.”
No one knows exactly why eyeballs elongate in low light, but children’s eyes are still developing through the early teen years, and proper visual feedback cues are needed from early infancy. Exposure to bright colors, strong contrast, and a full field of view may be critical. Being outside provides much more light than indoors, and the view is horizon-to-horizon, allowing good peripheral vision.
Dr. Flowers explains that bright light increases the release of dopamine, a chemical which helps transmit neurological signals, in the retina. Dopamine also plays an important role in the factors that regulate eye growth.
Vitamin D, which is stimulated by sunlight, may also be a factor. There is some evidence that kids with myopia had about 20 percent lower vitamin D levels than kids with normal vision. A 2008 study by dr. Rose and her colleagues also showed that exercise may be important, but only if it occurred outside. Children who played only inside sports were somewhat more likely to become myopic.
“Animal studies have convincingly shown that reducing both light and/or peripheral vision can result in myopia,” says Dr. Flowers. “Two small studies with humans showing that reduced outdoor time coincided with increased myopia have now been confirmed.”
Sending kids outdoors may not be the only solution to reducing the epidemic of nearsightedness, but scientific evidence supports that it can help. As kids’ social and play habits have changed and children are spending less time outside, they’re definitely missing out on some important visual feedback cues.
“Literature supports that there is a link between myopia prevention and children spending time outdoors. So encourage your kids to go outside and enjoy the day,” says Dr. Flowers.
Dr. Schwent agrees. “While we may not know exactly why being outside is important in reducing myopia, we do know that it seems to work. Given the stakes, sending your kids outdoors seems like a simple fix.”