Myopia is the first major disease affecting the visual health of young children. With the increase in the use of electronic products and the decrease in the time for outdoor exercise, the incidence of myopia is increasing year by year. Smith et al. firstly found that peripheral retinal defocus affects the course of myopia development in rhesus monkeys. Subsequent studies have shown that peripheral retinal hyperopic defocus can lead to the growth of the axial length (AL), leading to the development of myopia, while peripheral retinal myopic defocus can effectively slow down the growth of the AL, thus delaying the progression of myopia. Defocus signals can simultaneously change the thickness of the choroid, the vascular tissue behind the retina, and the pigment epithelium, and change the thickness and hardness of the sclera, inhibiting or promoting the growth of the axial length. Therefore, many methods have been designed to intervene in the development of myopia, including orthokeratology and peripheral defocusing glasses. The maintenance process of orthokeratology lens is complex and there is a risk of infection. Peripheral defocus glasses need to be worn for a long time, and the visual quality is unstable. It is still necessary to explore safer, more effective and more practical methods for myopia control. In addition, there may be some correlation between the development of myopia and the decrease of choroidal blood flow. Defocus signal may promote the increase of choroidal blood flow, which may be a way to prevent and control myopia. Therefore, the investigators integrated the digital defocus paradigm into VR devices and developed a digital defocus vision training (DDVT) system. The purpose of this study was to investigate the effectiveness and safety of DDVT in the prevention and control of myopia in children.