The development of myopia is closely related to environmental factors, and among the many factors, the study of the relationship between near work and myopia has a very long history; it is generally believed that near work is an important cause of myopia and promotes its progression, but recently, Mutti et al. (2007), in the OLSM study, found that near-visual activity was not a significant risk for myopia, while amount of outdoor activity appears to have a more important effect on myopia. Since then, the relationship between myopia and outdoor activity has received increasing attention from myopia researchers. I. Does outdoor activity actually have a protective effect on myopia? In her presentation, Professor Seang-Mei Saw from the National University of Singapore showed that increasing time spent outdoors can delay the age at which children develop myopia and reduce the risk of developing high myopia in adulthood. Professor Kathryn Rose from the University of Technology Sydney similarly pointed out that current research, including population-based longitudinal studies, has shown that increased time outdoors is a protective factor against the development of myopia in children, and has proposed plausible physiological mechanisms to explain this effect. In addition, Professor Ian Morgan from the Australian National University presented the results of a recent randomized controlled trial they conducted in Guangzhou. The results showed that increased outdoor activity was effective in reducing the prevalence of myopia. However, in the above-mentioned studies on the relationship between myopia and outdoor activity, the subjects were generally over 6 years of age, and there is less research on whether outdoor activity can also protect against the development of myopia in children under 6 years of age. Wilson Low et al. did a study that showed that for children 6 to 72 months of age, neither close work nor outdoor activities were substantially associated with the development of myopia, but were highly correlated with a parental genetic history of myopia. Therefore, they concluded that for early-onset myopia (<< span="">6 years of age), it is the genetic history of parental myopia that is most strongly associated with it, and not much with environmental factors such as near work and outdoor activities. Therefore, based on the current findings, increasing time spent outdoors has a relatively clear protective effect on the development of juvenile myopia; while there is no substantial protective effect on early-onset myopia (<6 years). < strong=""> II. How much outdoor activity can prevent myopia? According to Prof. Kathryn Rose, based on previous cross-sectional studies, about 2 hours of outdoor activity per day can reduce the risk of myopia, and Mutti et al. showed that the average time spent outdoors was 11.65 hours per week for people with non-myopia and 7.98 hours for people with future myopia. III. Why does outdoor activity prevent myopia? There are many hypotheses about the mechanism by which increased outdoor time protects against myopia. Some scholars believe that the difference in light intensity between indoors and outdoors is significant, with outdoor light levels generally above 10,000 lux and indoor light levels generally below 1,000 lux. Under high intensity outdoor light conditions, the retina releases more dopamine, which inhibits the growth of the eye axis. Some scholars also believe that staying outdoors for a longer period of time relatively reduces the amount of near activity, i.e., outdoor time is only a proxy, and the core is still a reduction in near activity. It has also been suggested that sports may have a protective effect on myopia, or that staying outdoors requires less accommodation, resulting in less accommodation lag, or that being outdoors at a distance results in less hyperopic defocus. In addition, some scholars believe that it is related to the different nature of the indoor and outdoor spectra, with the outdoor full spectrum and the indoor RGB spectrum dominating; at the same time, some scholars believe that the indoor and outdoor UV intensity is different. All of the above hypotheses have some degree of validity, but the current consensus is that high intensity outdoor light levels lead to increased synthesis and release of retinal dopamine, thus playing a major role in controlling eye axis growth. However, there is no certainty regarding the quantitative-effect relationship between light exposure and dopamine synthesis and release in the retina and inhibition of myopia.