Whether the myopia at the age of 9 with 300 diopters will develop into high myopia in the future depends on whether the eye use in the later stage is scientific or not as well as whether the child receives formal correction or not. Nine-year-old 300 degrees of myopia, belong to the more obvious myopia, due to the children’s eye regulation ability is weak, if by the use of eyes unhygienic and other external factors, myopia aggravation may be more acute, and in the future is prone to develop a high degree of myopia. A 9-year-old child with 300 degrees of myopia needs to receive timely treatment. Generally, it can be corrected by wearing frame glasses, which is a convenient, economical and safe way to correct myopia and needs to be worn continuously to relieve eye fatigue and prevent myopia from worsening. Usually, every 40 minutes of eye use, you need to take a break of 5 to 10 minutes to avoid prolonged eye use. If you pay attention to eye hygiene, develop good eye habits, and follow the doctor’s instructions to standardize the correction, myopia may no longer grow. At the age of 9 years old, 300 degrees, you need to follow the doctor’s instructions for correction, and regular visual acuity examination.