Myopia of 300 degrees at 12 years old is not very serious in terms of myopia, but it can affect the patient’s vision, and there is also the possibility of myopia developing into high myopia, so the patient needs to pay attention to it. The 12-year-old 300-degree myopia does not belong to high myopia, but it can affect vision, and 12 years old is still young, if myopia is not careful management, it is easy to aggravate the progression of myopia. However, if the myopia is corrected, the prognosis is good. Myopia can be corrected by wearing frames or corneal contact lenses to improve vision. If children with myopia do not want to wear glasses, patients can have their myopia corrected by surgery in adulthood, such as crystalline lens implantation and corneal laser surgery. It is recommended that myopic patients seek medical attention to evaluate their condition and follow the doctor’s instructions for treatment.