There are considerable researches to support that outdoor activity is an independent protective factor against myopia and its protective effect is positively associated with time spent outdoors. Outdoor activity can prevent the onset of myopia, but it is controversial whether it can control the progression of myopia in children and adolescents who are already myopic.The " light-dopamine" hypothesis is the most likely potential biological mechanism for outdoor activities to prevent and control myopia, as outdoor sunlight exposure stimulates the retina to secrete more dopamine, thereby suppressing the elongation of the eye-axis. The large amount of short-wave length light in the outdoor spectrum is focused in front of the retina, which retards myopia progression after receiving this signal. The increased synthesis of vitamin D by the skin in response to sunlight exposure may also play an important role in the prevention and control of myopia by outdoor activities. (Int Rev Ophthalmol, 2022, 46: 554-559)