This is a school-based, cross-sectional study to assess the incidence and prevalence, risk factors of myopia among schoolchildren in both eye-use environment, eye-use habits, lifestyle, and family and subjective factors before and during COVID-19. Large population and representative study subjects. Environmental exposure and daily within and out-of-school activities will be evaluated in a random subgroup.

Myopia is the most common refractive error and a major reason for reducing uncorrected visual acuity among schoolchildren. It was reported that during COVID-19, home confinement resulted in a significant increase in myopia due to the changed lifestyle of schoolchildren dramatically. However, it is unclear which kind of risk factors should be the first to bear the brunt before and during COVID-19. And which factors should be emphasized and confronted as the optimum strategy for myopia prevention and control? This cohort study aims to determine the risk factors, prevalence, and incidence of myopia, and SE changes among schoolchildren before and during COVID-19, hence identifying the factors that impact the onset and progression of myopia.

This is a 3-year cross-sectional study. This study plans to enroll 126,810 participants (aged 6-18 years) from Tianjin, China. All grade students from 10 regions of Tianjin City, China will be analyzed. Over a 3-year follow-up period, students will receive detailed eye examinations annually and complete questionnaires about eye-use environment, eye-use habits, lifestyle, and family and subjective factors. In a 5% random sample size of this cohort study, outdoor activity, light intensity, eye use habits, and eye use environment data will be obtained using objective measuring devices. Myopia was defined as spherical equivalent refractive (SER) of ≤ -0.5D.

Inclusion Criteria:

• All 6-18 years students

Exclusion Criteria:

• No eye diseases such as cataracts, glaucoma, keratoconus, etc.
• No psychiatric disorders
• Astigmatism ≤ -6.00D

All 6-18-year students with no significant systemic or eye diseases are eligible for vision screening