The normal naked eye vision is 1.0, where the naked eye vision is less than 1.0 may be myopia, myopia can be corrected to normal vision by wearing concave lenses. Generally within 300 degrees is mild myopia, 325-600 degrees is moderate myopia, and above 600 degrees is high myopia. There are many complications associated with high myopia, the more common ones being vitreous opacity, retinal detachment and macular degeneration of the fundus. There are many aspects of myopia prevention: 1. pay attention to eye hygiene, sitting posture, and distance from books. 2. strengthen outdoor activities and physical exercise, such as playing table tennis and flying kites. 3. eat less sugary foods and more vegetables and fruits. 4. have less contact with electronic products such as cell phones, computers, and TVs.