Glasses must be worn for 300 degrees of myopia. In general, moderate myopia has an impact on daily life and must be worn. Glasses are an important tool to assist myopic patients in seeing things, just like a cane. A cane itself does not aggravate the degree of disease in patients with leg disorders, but instead may aggravate the original disease by increasing the burden on the legs when walking without the help of a cane. Myopic patients may also aggravate the degree of myopia without glasses. In general, when looking at near objects, the refractive system of the orthoptic or mildly myopic eye will image after the retina, and the object on the retina is blurred, so in order to move the object behind the eye to the retina, the adjustment of the lens is often increased to make the object clear. In order to accommodate the presence of objects at the back of the eye, the posterior segment of the eye is constantly lengthened backwards, leading to a deepening of myopia. Myopia is classified as mild, moderate, or high according to the degree of myopia (degrees). Every 300 degrees is a ladder, i.e. 0-300 degrees is mild, 300-600 degrees is moderate, and over 600 degrees is high. 300 degrees of myopia is between mild and moderate myopia, and generally moderate myopia has an impact on daily life, and myopia will deepen if glasses are not worn. For the minor myopia patients, especially children younger than 7 years old, because the visual function is in the process of development, long-term non-wear glasses will affect the normal development of visual function, and may also cause amblyopia. Amblyopia is a state in which the eye has no other organic disease, and the corrected visual acuity does not reach 0.8 even with glasses, and amblyopia is irreversible when the eye’s visual function is basically mature. Therefore, 300 degrees of myopia must wear glasses, otherwise it may cause myopia to deepen, and minors may also cause amblyopia and other consequences.