Debate over cause of myopia surge

January 12, 2016

Myopia prevalence across the age spectrum is increasing, nearly doubling over the last 40 years in adolescents, but there are many theories as to why this is occurring. Learn about you can help your patients stave off nearsightedness.

Nearsightedness in children is on the rise, and some ophthalmologists believe using personal electronic devices is not helping.

Although there has not been any formal research done on the effect of smartphones, tablets, and more on myopia development in children, it was a hot topic at the American Academy of Ophthalmology's (AAO) annual meeting in Las Vegas earlier this year. Following the presentation of a study on the efficacy of low-dose atropine in staving off myopia, the AAO says many participants began to discuss possible causes of a surge in myopia cases over the last 40 years.

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According to a 2009 report in JAMA Ophthalmology, myopia prevalence was 66.4% higher in a poll conducted from 1999 to 2004 compared with figures from the early 1970s. Total myopia prevalence in 12- to 54-year-olds was about 26% in 1971 to 1972, according to the report, and 43% by 1999 to 2004. In the 1970s, individuals aged 18 to 24 years had the highest rates of myopia, but that shifted 25- to 34-year-olds in the 1999 to 2004 study. Additionally, prevalence among children aged 12 to 17 years increased from 28.8% in the 1970s to 34.5% over a decade ago.

There are many reasons these increases could be occurring, says K David Epley, MD, clinical spokesperson for AAO and a pediatric ophthalmologist in Washington state. Several theories link high amounts of “near work” and less exposure to outdoor light. While no direct connection has been made to electronics devices, it is true that the devices invite users to engage in more near work and may reduce physical-specifically outdoor-activity participation.

“Constant eye strain can be a problem whether it’s reading on paper or on a screen because it can cause discomfort,” Epley says. “Lighting of screens doesn’t make eyes work harder but some people can be sensitive to the lighting. Looking at something up close hour after hour aren’t what our eyes were intended for.”

Several studies have drawn connections between near work-not just in front of an electronic device or computer-and myopia prevalence.

Decades ago, far fewer people suffered from myopia, according to data from the Keck School of Medicine of the University of Southern California (USC). In China, myopia rates have increased from 10% to 20% roughly 60 years ago to 90% today-and 96% of 19-year-old men have myopia, according to the USC report. Asian ethnicities have a greater genetic predisposition for myopia, but Rohit Varma, director of the USC Eye Institute believes long work and study hours-typically up to 12 hours each day-in Asia contribute to the problem.

NEXT: The impact of near work

 

“Children today spend many more hours in near-work and low-light activity rather than spending more time outdoors where distant vision and natural light helps eyes to shape normally as spherical instead of the oblong or egg-shaped that we are currently seeing,” says Varma. “In addition to improving childhood vision health, more outdoor activity and less time spent on video games, computers, smartphones and tablets will also potentially help reduce the increase we have seen in childhood obesity.“

Varma isn’t the only one that supports increased near-work and outdoor lighting as a reason for increases in myopia.

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A 2008 study of Australian school children examined the time spent in near work and reading with a spherical equivalent refraction (SER), and found that while myopia wasn’t directly correlated to near work and reading with an SER, there were associations with close reading distance and continuous reading.

Another study, published in January 2015, found that children in low-income areas of Asia seem to have less occurrences of myopia, and the researchers hypothesized that the trend was related to greater use of blackboards over books. Prevalence of myopia in a low-income province of China was 12.7% compared to 23% in a middle-income province, according to the report.

Low-income students who can’t afford books learn primarily off blackboards, which may have a “protective effect” against myopia, according to the report, because blackboards don’t require close-up focusing.

A 2014 German study also connects myopia to education level, revealing that extended periods of near work from studying may play a role in myopia development. According to the study, 24% of the study cohort with no high school education or training were nearsighted compared to 35% of high school graduates and 53% of university graduates.

Spending more time outdoors may help delay or reduce myopia development, according to several recent studies. A randomized clinical trial of 6-year-olds in Guangzhou, China, found that as little as 40 additional minutes of outdoor activity reduced incidence rates of myopia over the next 3 years.

NEXT: Effect of outdoor light

 

The spectrum of light that the outdoors is different than that inside, and continually being inside-especially looking at lit screens-may cause of aggravate myopia in children, says Epley.

Anyone who spends a lot of time in front of a screen is encouraged to take breaks to reduce eye strain, he adds. In children, parents, and pediatricians must promote health behaviors and breaks.

“We encourage parents to talk with their kids about screen time for a lot of other reasons other than myopia-social development, anger management skills, cognitive skills,” Epley says. “We encourage pediatricians also to recommend to parents that kids take breaks from reading or tablets or whatever to reduce that intensity.”

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Humans typically blink about 18 times per minute, but research has shown that people generally blink half as much while using electronic devices or computers. Users should keep screens about 25 inches from their face and post a reminder to blink around their workspace. The AAO also recommends everyone follow the 20-20-20 rule-for every 20 minutes of screen time, users should shift their gaze to an item about 20 feet away for at least 20 seconds to reduce eye strain.

In terms of other prevention measures, Epley says a 5-year clinical trial presented at the AAO meeting shows that low-dose atropine-typically used to treat amblyopia-may be effective in slowing myopia development. After 5 years of use, children in the study using 0.01% atropine drops were the least myopic compared to children treated with higher doses, and the low-dose drops slowed myopia progression by an estimated 50% compared to children not treated at all. More study is needed, but Epley says this is a treatment pediatricians could possibly one day employ in their practices-assuming they are able to gauge its efficacy.

“There is no reason pediatricians couldn’t prescribe this in their practices, but a general ophthalmologists would want to do it to ensure the amount of nearsightedness isn’t changing on a regular basis,” Epley says. “If you happen to have an autorefractor in your office, okay. That’s an important metric to know.”

Where pediatricians do play a vital role is in performing regular vision screenings, ideally before the start of kindergarten, and referring children who appear to have or be at risk of developing vision problems to an ophthalmologists. Simple screening kits can be purchased for $69 through the American Academy for Pediatric Ophthalmology and Strabismus (AAPOS), says Epley. The AAPOS also offers guidance on how often to perform screenings throughout childhood and what types of changes warrant referral to an ophthalmologist.