Myopia and the COVID-19 Pandemic in Hong Kong

Article: The Global Pandemic Could Be Causing More Shortsightedness in Kids Than Ever Before
Source: ScienceAlert
Published: August 4, 2021

The COVID-19 pandemic has brought attention to the increased global incidence of myopia in the pediatric population, as adjustment to lockdown led to less time spent outdoors and more time spent interacting with screens and near work. An often-cited study published in JAMA Ophthalmology  reported overall increased rates of myopia among more than 120,000 homebound children in China. Researchers in Hong Kong expanded upon the topic, as reported in a smaller cohort study involving 1793 children between the ages of 6 and 8, 1084 of whom were recruited before the COVID-19 pandemic and compared with 709 children who were recruited at the beginning of the COVID-19 pandemic. The authors report, "The overall incidence was 19.44% in the COVID-19 cohort, and 36.57% in [the] pre-COVID-19 cohort. During the COVID-19 pandemic, the change in SER [spherical equivalent refraction] and axial length was –0.50±0.51 D and 0.29±0.35 mm, respectively." Note that the incidence is actually reported to be higher in the pre-COVID-19 cohort.

However, because these are two different cohorts, recruited at two different time periods (and over different durations), the authors caution against a direct comparison between them. Instead, they "estimated the risk ratio of incidence of myopia between the two groups using a relative risk regression model (log-binomial model)," and based on that model, they found that "myopia incidence in the COVID-19 cohort was higher than in the pre-COVID-19 cohort (p=0.03) after adjusting for age, gender, follow-up duration, parental myopia, time of outdoor activity and near work." The authors also compared this study to an earlier study from 2004 to further support their data, stating, "The myopia incidence (13.15% over 1 year) in the previous cohort was lower than that of our COVID-19 cohort (19.44% over 8 months, p<0.001) despite having a longer follow-up of 1 year compared with 8 months in the COVID-19 cohort, indicating that the incidence of myopia increased during the COVID-19 pandemic." They attribute this to a decrease in outdoor activities from approximately 1 hour 15 minutes to merely 25 minutes per day and an increase in screen time from 2.5 to nearly 7 hours per day. Despite very indirect methodology in this study, based on comparison with similar studies in Asia, it is reasonable to extrapolate, with caution, that their model captures trends consistent with a global increase in myopia incidence during the COVID-19 pandemic. The researchers conclude with a motivation for the study, saying, "Our results serve to warn eye care professionals, and also policy makers, educators and parents, that collective efforts are needed to prevent childhood myopia—a potential public health crisis as a result of COVID-19."

My rating of this study: ⭐

Zhang X, Cheung SSL, Chan H, et al. "Myopia incidence and lifestyle changes among school children during the COVID-19 pandemic: a population-based prospective study." British Journal of Ophthalmology.  2 August 2021. https://doi.org/10.1136/bjophthalmol-2021-319307