School closure during COVID-19 may have upped myopia prevalence in children

School closures during the COVID-19 pandemic may have led to an increase in the prevalence of myopia in children aged 6–8 years, according to a cross-sectional, prospective study from China.

“The findings of this study suggest that home confinement during the COVID-19 pandemic was associated with a substantial myopic shift for younger school-aged children,” said the authors.

“The prevalence of myopia increased 1.4 to three times in 2020 compared with the previous 5 years,” they said.

This study involved 123,535 children aged 6–13 years (52.1 percent male) from 10 elementary schools in Shandong, China, who underwent annual school-based photoscreenings between 2015 and 2020 to identify noncycloplegic photorefraction. The final analysis comprised 194,904 test results of 389,808 eyes. None of the participants were receiving low-dose atropine for myopia.

Between 2015–2019, mean spherical equivalent refraction (SER) was generally stable in all age groups. However, photoscreenings in 2020 showed a decrease in SER in children age 6 (-0.32 diopters), 7 (-0.28 diopters), and 8 years (-0.29 diopters) compared with the years 2015–2019. [JAMA Ophthalmol 2021;doi:10.1001/jamaophthalmol.2020.6239]

The reduction in SER in 2020 vs 2015–2019 was less notable in older children (-0.12 diopters [age 9 years], -0.11 diopters [age 10 years], -0.06 diopters [age 11 years], -0.05 diopters [age 12 years], and -0.05 diopters [age 13 years]).

The prevalence of myopia (SER ≤-0.50 diopters) in the year 2020 exceeded the highest prevalence noted in the years 2015–2019 in children age 6 (21.5 percent vs 5.7 percent [2019]), 7 (26.2 percent vs 16.2 percent [2018]), and 8 years (37.2 percent vs 27.7 percent [2018]; p<0.001 for all).

Among children aged 9 years, the highest prevalence of myopia was noted in 2020 (45.3 percent), though it did not vary substantially from 2018, the year with the second highest prevalence (43.5 percent; p=0.09). For children aged 10–13, the highest prevalence of myopia in these age groups was not in 2020.

While the SER reductions were noted in both sexes, myopia tended to develop earlier in girls than boys. There was also a tendency for the right eye to be more myopic than the left eye.

School closures were among the measures introduced to limit the spread of COVID-19 in China. This led to an estimated >220 million school-aged children and adolescents being confined at home with their lessons delivered online. Despite the success of these measures in infection control, the reduction in time spent outdoors coupled with the increase in screen time may have impacted eye health.

“Lessened outdoor activity is known to be significantly associated with a higher incidence of myopia in school-aged children,” said the authors. “Concerns have been raised about whether home confinement may worsen the burden of myopia. To our knowledge, we provide the first evidence that the concern may be justified, especially for younger children aged 6–8 years,” they said.

To counteract this, the authors recommended that parents limit their children’s screen time and encourage allowable outdoor activity, while maintaining safe distancing practices.

The lack of increase in myopia prevalence in children aged 9–13 years, despite longer online learning hours, suggests that refractive status in younger children may be more sensitive to environmental changes, they added.

“Children aged 6–8 years may be experiencing an important period for myopia development. Within this age window, the plasticity of myopia is high and myopia control may be easier,” they said. Further study is necessary to assess this and if proven, may open the door for better myopia control strategies. Ongoing annual school-based photoscreening may help discern if this myopia is temporary or permanent.

The authors acknowledged that certain factors limited the findings including the lack of information on exact amount of screen time exposure or outdoor activity and ocular biometry.