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Published on Leave a comment on Time Spent Outside and Nearsightedness

Another study found that young children who more time spent outside in natural light for 3 years resulted in fewer cases of myopia (near-sightedness). Specifically, the good results were found from one additional 40-minute class of outdoor activities each school day, as well as parents encouraging their children to play outdoors after school hours, especially during weekends and holidays. So....those of you who are parents of children huddled inside - get them outside daily in the sunlight to soak up sunshine for vitamin D and to help their vision. From Science Daily:

Additional time spent outdoors by children results in decreased rate of nearsightedness

The addition of a daily outdoor activity class at school for three years for children in Guangzhou, China, resulted in a reduction in the rate of myopia (nearsightedness, the ability to see close objects more clearly than distant objects), according to a study in the September 15 issue of JAMA.

Myopia has reached epidemic levels in young adults in some urban areas of East and Southeast Asia. In these areas, 80 percent to 90 percent of high school graduates now have myopia. Myopia also appears to be increasing, more slowly, in populations of European and Middle Eastern origin. Currently, there is no effective intervention for preventing onset. Recent studies have suggested that time spent outdoors may prevent the development of myopia, according to background information in the article.

Mingguang He, M.D., Ph.D., of Sun Yat-sen University, Guangzhou, China, and colleagues conducted a study in which children in grade 1 from 12 primary schools in Guangzhou, China (six intervention schools [n = 952 students]; six control schools [n = 951 students], were assigned to 1 additional 40-minute class of outdoor activities, added to each school day, and parents were encouraged to engage their children in outdoor activities after school hours, especially during weekends and holidays (intervention schools); or children and parents continued their usual pattern of activity (control schools). The average age of the children was 6.6 years.

The 3-year cumulative incidence rate of myopia was 30.4 percent (259 cases among 853 eligible participants) in the intervention group and 39.5 percent (287 cases among 726 eligible participants) in the control group. Cumulative change in spherical equivalent refraction (myopic shift) after 3 years was significantly less in the intervention group than in the control group.

"Our study achieved an absolute difference of 9.1 percent in the incidence rate of myopia, representing a 23 percent relative reduction in incident myopia after 3 years, which was less than the anticipated reduction. However, this is clinically important because small children who develop myopia early are most likely to progress to high myopia, which increases the risk of pathological myopia. Thus a delay in the onset of myopia in young children, who tend to have a higher rate of progression, could provide disproportionate long-term eye health benefits," the authors write.

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Children spending time outside (more than 14 hours a week) have lower rates of nearsightedness, even if they spend a lot of time reading. From Science Daily:

Scientists study effects of sunlight to reduce number of nearsighted kids

Kids who spend more time outside are less likely to need glasses for nearsightedness – but scientists don’t know why. Researchers are now looking more closely at physical changes in the eye influenced by outdoor light exposure in the hopes of reducing cases of myopia, which affects one-third of the American population.

Despite what many parents may think, kids who spend a lot of time reading or squinting at tiny electronic screens aren't more likely to become nearsighted than kids who don't. However, that risk is only reduced if the child spends plenty of quality time outside. The "outdoor effect" on nearsightedness, or myopia, is a longstanding observation backed by both scientific and anecdotal evidence. It's so compelling that some nations in Asia, which have among the highest myopia rates in the world, have increased the amount of daily outdoor time for children in the hopes of reducing the need for glasses.

But so far, no one has defined exactly what it is about being outside that seems to offer a protective effect against the condition, which causes distant objects to appear blurry.

"Data suggest that a child who is genetically predisposed to myopia are three times less likely to need glasses if they spend more than 14 hours a week outdoors," says optometrist Donald Mutti, OD, PhD, of The Ohio State University College of Optometry. "But we don't really know what makes outdoor time so special. If we knew, we could change how we approach myopia."

Supported by a pilot grant from Ohio State's Center for Clinical and Translational Science (CCTS), Mutti is now focusing his research on the variables he feels have the most potential: invisible ultraviolet B rays (UVB) and vitamin D, and visible bright light and dopamine."Between the ages of five and nine, a child's eye is still growing. Sometimes this growth causes the distance between the lens and retina to lengthen, leading to nearsightedness," explained Mutti. "We think these different types of outdoor light may help preserve the proper shape and length of the eye during that growth period."

UVB light is invisible to the human eye, but triggers several cellular functions in the body, including the production of vitamin D. Vitamin D is thought to support the function of the smooth muscle tissue found around the lens in the eye. This muscle not only helps focus light on the retina, but may also maintain the proper eye shape and length between the lens and the retina, something that can become distorted during the rapid growth of a child's eye.

Some studies, including one by Mutti, show that people with myopia have lower blood levels of vitamin D -- indicating that they have spent less time outdoors, with possible negative effects on the eye..."We don't know if vitamin D is simply a proxy for measuring outdoor time, or if it is actually exerting a biological effect on how the eye works and develops," said Mutti.

There's another part of sunlight that could help prevent myopia: exposure to visible bright light. Even on a cloudy day, visible light outdoors is at least 10 times brighter than the light indoors.When exposed to outdoor light, specialized cells in the retina help control how big or little the pupil dilates to let more or less light in. The cells connect to others that release dopamine -- an important neurotransmitter in the eye and brain. Previous research suggests that dopamine also slows down the growth of the eye, but there isn't technology currently available that can measure dopamine release in the eye directly.

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Since myopia increased 66% between the early 1970s to early 2000s in the United States, it is thought that there are environmental factors at play, namely higher levels of education, all our close-up activities with new technology (reading, computers, tablets, etc.) straining our eyes, and spending too much time indoors. From The Atlantic:

Nearsightedness and the Indoor Life

Over the past 15 years, the world has witnessed an explosion of cases of myopia, or nearsightedness. A quarter of the world's population, or 1.6 billion people, now suffer from some form of myopia, according to the Myopia Institute. If unchecked, those numbers are estimated to reach one-third of the world's population by 2020. 

The 2009 study is hardly the first to suggest that an increase in years of formal education and access to technology across society may account for higher myopia rates in recent years. Ophthalmologists and optometrists have cautioned that close-up activities like reading and using computers, tablets, and smartphones interfere with normal blinking and put a strain on the eyes. When abused, they can lead to double vision, myopia, and serious conditions such as retinal detachment and vision loss. The overuse of handheld electronics such as iPads and tablets by young children is especially worrisome, since their eyes are still developing and are more likely to be affected, according to researchers.

Kathryn Rose, a researcher of visual disorders at the University of Sydney's college of health sciences, recently concluded  that spending too much time indoors also has a huge impact on eyesight deterioration. Rose said in a CNN interview that she was not sure how time spent using digital media relates to myopia progress, but that outdoor light has been shown to have a positive effect on vision. Studies from the U.S., Singapore, and China confirm a link between the time spent outdoors and the prevention of myopia, Rose said. However, both the level of light and the duration of exposure to outdoor light must reach a certain threshold to have a preventive effect, according to one of her studies. Spending at least 10 to 14 hours outside per week may prevent the early onset of myopia, she concluded.

Dr. Maria Liu, head of the Myopia Control Clinic that opened last year, explained that prevention and treatment success depend on early detection. Nearsighted children under 10 could benefit the most from intervention. This age group is also the most susceptible to eye damage from prolonged use of visual media, according to the myopia specialist."The eyeballs are very adaptive while they are developing," Liu told me. "If we impose a lot of near work on the eyes as they are developing, the eyes will interpret nearsightedness as being the normal state."

She explained the rise in myopia prevalence is likely caused by a shift in lifestyle from spending time outdoors to an indoor-oriented existence. Electronic devices play a major role in this shift, especially with young children being introduced to technology at an earlier stage in their life, and using handheld devices that require a smaller working distance than that for a physical book or television.

The Myopia Control Clinic specialists use corrective lenses (novel contact lenses) to slow down myopia in children. If applied early enough, corrective lenses have proven effective in treating the disorder. In cases with very high myopia progression, however, scleral reinforcement surgery is used to reduce or stop further damage caused by high myopia, which often can be degenerative. Atropine is the only drug that so far has proven effective in slowing myopia progression. The drug is used as a second line of treatment after all optical treatments fail.

Although modern lifestyle makes it harder to fight the disorder, there is something parents can do to prevent its early onset."Whether it is because hormonal levels are different outdoors, or because the light intensity is stronger, or because we do less close-up work, it has been shown consistently that outdoor activity is very protective and tends to slow the rate of progression."

Taking frequent 10-minute breaks from near-work and looking in the distance is also recommended, including for young adults who spend a lot of time working on computers or laptops and may suffer from accommodating spasms that cause blurry distance vision and dry eyes. Some specialists recommend limiting time in front of computers, TVs, and handheld devices to 1.5 hours a day, especially for young children.