SummaryBackgroundHigh prevalence of myopia of adolescent has been a global public health concern. Their risk factors and effective prevention methods for myopia across schoolchildren developmental stages are critically needed but remain uncertain due to the difficulty in implementing intervention measurements under normal life situation. We aimed to study the impact of the COVID-19 quarantine on myopia development among over one-million schoolchildren.MethodsWe designed the ongoing longitudinal project of Myopic Epidemiology and Intervention Study (MEIS) to biannually examine myopia among millions of schoolchildren for ten years in Wenzhou City, Zhejiang Province, China. In the present study, we performed three examinations of myopia in 1,305 elementary and high schools for schoolchildren in June 2019, December 2019 and June 2020. We used the normal period (June-December 2019) and COVID-19 quarantine period (January-June 2020) for comparisons. Myopia was defined as an uncorrected visual acuity of 20/25 or less and a spherical equivalent refraction (SER) of -0.5 diopters (D) or less. High myopia was defined as an SER of -6.0 D or less.FindingsIn June 2019, 1,001,749 students aged 7-18 were eligible for examinations. In the 6-month and 12-month follow-up studies, there were 813,755 eligible students (81.2%) and 768,492 eligible students (76.7%), respectively. Among all students, we found that half-year myopia progression increased approximate 1.5 times from -0.263 D (95% CI, -0.262 to -0.264) during normal period to -0.39 D (95% CI, -0.389 to -0.391) during COVID-19 quarantine (P < 0.001). Multivariate Cox regression analysis identified grade rather than age was significantly associated with myopia (Hazard ratio [HR]: 1.10, 95% CI, 1.08 to 1.13; P < 0.001) and high myopia (HR: 1.40, 95% CI, 1.35 to 1.46; P < 0.001) after adjustment for other factors. The prevalence, progression, and incidence of myopia and high myopia could be categorized into two grade groups: I (grades 1-6) and II (grades 7-12). Specifically, COVID-19 quarantine for 6 months sufficiently increased risk of developing myopia (OR: 1.36, 95% CI, 1.33 to 1.40) or high myopia (OR: 1.30, 95% CI, 1.22 to 1.39) in Grade Group I, but decreased risk of developing myopia (OR: 0.45, 95% CI, 0.43 to 0.48) or high myopia (OR: 0.57, 95% CI, 0.54 to 0.59) in Grade Group II.InterpretationThe finding that behavioral modifications for six months during COVID-19 quarantine sufficiently and grade-specifically modify myopia development offers the largest human behavioral intervention data at the one million scale to identify the grade-specific causal factors and effective prevention methods for guiding the formulation of myopia prevention and control policies.FundingKey Program of National Natural Science Foundation of China; the National Natural Science Foundation of China; Scientific Research Foundation for Talents of Wenzhou Medical University; Key Research and Development Program of Zhejiang Province.Research in contextEvidence before this studyMyopia is the most-common refractive error worldwide. Myopia with younger onset may result in developing high myopia, which is associated with sight-threatening ocular diseases such as maculopathy, retinal detachment, opticneuropathy, glaucoma, retinal atrophy, choroidal neovascularization. In light of the increasing prevalence of myopia and high myopia has been a global public health concern, the impact of COVID-19 lockdown on myopia development has gained substantial attention. We searched PubMed, Google Scholar, and MEDLINE databases for original articles reported between database inception and November 10, 2020, using the following search terms: (coronavirus OR COVID* OR SARS-COV-2 OR lockdown OR quarantine) AND (myopia OR short-sightedness OR refractive error). To date, there was no original study reported to uncover the influence of COVID-19 quarantine on myopia progression.Added value of this studyThis study provides the largest longitudinal intervention data on myopia progression in Chinese schoolchildren covering all grades of schoolchildren at one-million scale. COVID-19 quarantine model uncovers that behavioral modifications for six months may lead to significant increase of overall prevalence of myopia associated with their increased screen times and decreased outdoor activity times. Importantly, their effects on developing myopia or high myopia of students are grade-dependent, which were risk factors for elementary schools period but protective factors for high schools period partly due to reduced school education burden.Implications of all the available evidenceThis one-million schoolchildren myopia survey offers evidence that six months behavioral modifications sufficiently and grade-specifically change the progression of myopia and high myopia. In view of the increased use of electronic devices is an unavoidable trend, effective myopia prevention strategy according to grade among students is urgently needed. Since COVID-19 outbreak is still ongoing and spreading, international collaborate efforts are warranted to uncover the influence of COVID-19 on myopia progression to further substantiate these findings.
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