In 2020, the overall myopia rate among children and adolescents in my country was 52.7%. The COVID-19 pandemic has increased students' time of indoor eye-using, and it showed that the light exposure intensity of myopic students is lower than that of non-myopia students. Studies have found that the light wave bandwidth has a significant impact on the emmetropization of the eye, and white light can promote emmetropia more than monochromatic light. It shows that outdoor exercise has a protective effect on the occurrence and development of myopia in children and adolescents, but the specific mechanism is still unclear. Retinal blood flow is sensitive to myopic stimuli, and is a short-term indicator of the relationship between light environment and myopia. This study selected retinal blood flow as the primary outcome, aiming to compare the effects of different outdoor light exposure modes on retinal blood flow after 1 hour of intense eye use, and provide clues for the prevention and control of myopia.

In 2018, eight departments including the Ministry of Education jointly issued the Implementation Plan for Comprehensive Prevention and Control of Myopia in Children and Adolescents. As of 2020, the overall myopia rate among children and adolescents in my country was 52.7%. The COVID-19 pandemic has increased students' time of indoor eye-using, and it showed that the light exposure intensity of myopic students is lower than that of non-myopia students. Studies have found that the light wave bandwidth has a significant impact on the emmetropization of the eye, and white light can promote emmetropia more than monochromatic light. It shows that outdoor exercise has a protective effect on the occurrence and development of myopia in children and adolescents, but the specific mechanism is still unclear. Retinal blood flow is sensitive to myopic stimuli, and is a short-term indicator of the relationship between light environment and myopia. Also, there is a theory that reduced choroidal blood flow causes scleral hypoxia, which leads to the development of myopia. Therefore, this study selected retinal blood flow as the primary outcome, aiming to compare the effects of different outdoor light exposure modes on retinal blood flow after 1 hour of intense eye use, and provide clues for the prevention and control of myopia.

Inclusion Criteria:

• School students aged from 7 to 15, regardless of sex or gender;
• Diopter between -2.0D and 3.0D, and astigmatism not exceed 0.75D;
• No organic disease and in good general condition;
• Have obtained the consent of their parents or guardians, and can cooperate.

Exclusion Criteria:

• Suffering from amblyopia, strabismus, color weakness, congenital cataract, glaucoma and other eye diseases;
• Other circumstances judged by the investigator to be unsuitable to participate in the research.

The participants were randomly divided into two groups without knowing the exposing mode.