The high prevalence of myopia has become a global public health problem. The study amied to investigate the prevalence and progression of myopia associated with social environmental factors in Tianjin, a Chinese megacity in north China.

The high prevalence of myopia has become a global public health problem, especially in East and South Asian countries. It's still not clear for the prevalence and progression of myopia associated with social environmental factors. Thus, the investigators will conducted a long-term observational study to the effect of the socioeconomics, medical resources and school-related environmental parameters and others on the prevalence and progression of myopia among Chinese school-aged children and adolescent.

Inclusion Criteria:

• aged 6 to 18 years
• no ocular diseases and systemic diseases
• consent to undergo an eye examination

Exclusion Criteria:

• schoolchildren unwilling to participate

All school-aged children and adolescents completed the vision screening in the included school.