Premyopia at Preschool Age: Population-based Evidence of Prevalence and Risk Factors from a Serial Survey in Taiwan.

PURPOSE: Premyopia at a young age carries a great risk of developing early-onset myopia, especially in regions with myopia epidemics, such as the developed areas in East Asia. This study aims to report the prevalence of premyopia and its risk factors in a Taiwan preschool population and lifestyle changes among premyopic preschoolers before and during the Coronavirus Disease 2019 (COVID-19) pandemic. DESIGN: Repeated countywide population-based, cross-sectional study in Yilan County, northeastern Taiwan. PARTICIPANTS: From 2014 to 2020, a total of 23 930 kindergarteners aged 5 to 6 years were identified in the Yilan Myopia Prevention and Vision Improvement Program (YMVIP). Of those, 21 761 (11 335 [52.1%] boys; mean age, 5.15 ± 0.37 years) were included for final analysis. METHODS: Annual kindergarten-based eye examinations and myopia prevention strategies have been conducted since the commencement of the YMVIP in 2014. Refractive error was determined by cycloplegic autorefraction. The data of potential risk factors for myopia were gathered by caregiver-administered questionnaires. MAIN OUTCOME MEASURES: The prevalence of premyopia (spherical equivalent [SE] > -0.5 diopter [D] and ≤ +0.75 D in the eye with less SE value). RESULTS: The prevalence of myopia (SE ≤ -0.5 D), premyopia, and hyperopia (SE > +0.75) was 10.7% (95% confidence interval [CI], 10.3-11.1), 52.0% (95% CI, 51.3-52.7), and 37.3% (95% CI, 36.7-37.9), respectively. Multinomial logistic regression analysis showed that premyopia prevalence was significantly associated with male gender (odds ratio [OR], 1.25; 95% CI, 1.18-1.32), caregiver myopia (OR, 1.46; 95% CI, 1.37-1.56), screen time ≥ 1 hour per weekdays (OR, 1.10; 95% CI, 1.04-1.17), 2-year exposure to myopia prevention strategy (OR, 0.59; 95% CI, 0.54-0.65), and college or higher education level of caregiver (OR, 0.91; 95% CI, 0.85-0.96). Even without large-scale school closure in Taiwan, there was a slight upward trend of increased time spent on screen-based devices during the COVID-19 pandemic. CONCLUSIONS: Our findings showed that premyopia was the most common refractive error in a Taiwan preschool population. Premyopia was also associated with both parental and environmental myopiogenic factors. Longitudinal studies are warranted to examine the lifestyle change and myopic shift of premyopic preschoolers in the postpandemic era.