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Study at Home During COVID-19 Lockdown Is Associated with a Dramatic Increase in the Prevalence of Myopia in Hong Kong Children

Background: Due to the COVID-19 pandemic, schools in Hong Kong were closed down for four months. During this period, local schools devised online learning resources for students to study at home. While the demand to access this online resource may directly increase screen time, it was unknown whether it would promote myopia development. We compared the results of vision screening conducted in the same primary school for 8-10 year-old children before and after the COVID-19 pandemic. 
 
Methods: This was a cross sectional study. Two vision screenings, targeted at children aged 8 to 10 years old, were conducted in the same primary school in October 2018 and June 2020. Non-cycloplegic refraction and axial length were measured by an open‐field auto‐refractometer (Shin‐Nippon, NVision K5001, Japan) and an IOL Master (Carl Zeiss Meditec AG, Germany), respectively. A questionnaire focusing on risk factors of myopia was completed by parents of participants. 
 
Findings: There were no significant differences in age, gender, monthly family income, or parental myopia between the two cohorts. Alarmingly, the overall myopia proportion (SE ≤ -1·00 D) was significantly higher after the school lockdown (75·7% vs 37·5%, Chi-square test, 𝜒 2 = 40·758,&|amp;|lt;0·001). In addition, the axial length (23·64±1·00 mm vs. 23·39±0·89 mm, unpaired t-test, t = -2·151, p=0·02) and time spent on handheld digital devices (1·40 hrs/day vs. 1·60 hrs/day, Mann-Whitney U test, U=7590·5, p=0·01) were both significantly higher over this period. 
 
Interpretation: A dramatic increase in myopia proportion was noted after the school lockdown period. Increased screen time may contribute to an increased risk of myopia development among other potential risk factors. 
 
Funding: Center for Myopia Research, School of Optometry, The Hong Kong Polytechnic University. 
 
Declaration of Interests: The authors declare that they have no competing interests. 
 
Ethics Approval Statement: This study followed the tenets of the Declaration of Helsinki and was approved by the ethics committee of The Hong Kong Polytechnic University (HSEARS20180726001). Informed written consent was obtained from parents after explaining the nature and purpose of the study.