Outdoor activities associated with less myopia
WASHINGTON – A large study of children in China found that participation in more outdoor activities and having fewer myopic parents were both associated with a lower incidence of and less progressive myopia.
Here at Optometry’s Meeting, Shi-Ming Li, MD, of the Beijing Tongren Eye Center, Beijing Tongren Hospital, Beijing Ophthalmology Visual Science Key Lab, Beijing Institute of Ophthalmology and Capital Medical University, Beijing, China, presented results of the Anyang Childhood Eye Study, where 3,113 urban children from primary school and 2,363 from junior high have been followed annually since 2011. They ranged in age from 6 to 18 years.
According to the study abstract, of the 1,785 eligible children between the ages of 10 and 15 years, the prevalence of myopia was 68.1%, the incidence was 22.1%, and the progression of myopia was -0.49 D/year. The prevalence of high myopia, defined as at least -6.00 D, was 2.9%, the incidence was 1.7%, and the progression was -0.37 D/year.
“The myopia shift from grade 1 to grade 7 was +0.95 D to -1.60 D,” Li told attendees. “And the age of myopia onset has become younger: 10 years in grade 7 and 6 years in grade 1.”
The study abstract specified that having one or both myopic parents was associated with greater odds of prevalent myopia, high myopia, incident high myopia and progressive myopia.
“It makes sense that high myopia might be mainly affected by genetic factors such as inheriting it from parents,” Li said.
He added that no relationship was found between myopia and amount of near work.
“No studies show a strong relation between amount of near work and myopia,” he said. “Maybe the method of measuring amount of near work is not accurate. Mostly we use a questionnaire. Perhaps [we should not look at] total time of near work, but duration of continuous reading as a factor. If children read for 2 hours then take a break, I think it is worse. We should separate reading into sections, like 30 to 40 minutes, then break.”
In China, 40 million people have myopia, and 10 million have pathological myopia, Li told attendees. The incidence of high myopia is increasing, the age of onset is getting younger, and there are few clinically effective interventions.
Li’s group also performed a trial involving Chinese eye exercises with 195 Chinese subjects.
He explained that in the first group, doctors of traditional Chinese medicine trained the subjects and performed acupuncture. The second group performed exercises, but the acupuncture was done 2 mm to 3 mm away from the correct location. The third group did nothing.
“The Chinese eye exercises had a statistically significant effect in reducing accommodative lag [the primary study outcome] in children in the short term,” Li said.
“The exercises are done for only 5 minutes,” he said. “If following these exercises can reduce accommodative lag, maybe for 1 year or 2 years there will be some effect of slowing myopia.
“In China, we have the orthokeratology lens, [studies on] the concentration of atropine, time outdoors, the classroom with glass, but maybe there’s another way,” Li concluded. “There’s still a ways to go to controlling myopia in China.”— by Nancy Hemphill, ELS, FAAO
Li SM. Prevalence, incidence, progression and risk factors for myopia and high myopia among children in central China: The Anyang Childhood Eye Study. Presented at: Optometry’s Meeting; Washington; June 21-25, 2017.
Disclosure: Li reported no relevant financial disclosures.