Objective       To investigate the prevalence and the impact factors for myopia among the pupils in Chongqing city.       Methods       Stratified random cluster sampling was used to randomly select 3 primary schools

which belong to 3 different types of school (key

ordinary and private school) from Chongqing urban area. Then 1 to 3 classes from grade 1 to 6

which were extracted randomly according to the total number of classes in each grade

were considered as the object of this investigation. Finally

there were 45 classes

containing 1 880 primary students from the 1st to 6th grade enrolled in this study. The investigation included visual test and questionnaire.       Results       The prevalence

of myopia in primary school students was 30.59%

and it was different in the students from different grade levels

different ages and different types of school. The incidence of myopia morbidity was higher for girls than for boys (

P

0.05). Most students had myopia of mild to moderate

and for those from the 6th grade (12 to 13 years old)

they had the highest growth rate. Parental myopia

studying late at night

liking eating sweet food or snacks were the risk factors of myopia; upright sitting position

no bad habit of reading in bed

the light intensity in classroom

liking eating foods rich in protein were the protective factors of vision.       Conclusion       The prevalence of myopia in the our cohort is higher. Its influencing factors are personality characteristics

health behaviors

and genetic factors. Targeted intervention measures are demanded for this cohort.