Myopia glasses are equivalent to a concave lens, so they can play a role in reducing the image of the object, therefore, myopic people see a much smaller image than normal people after wearing glasses, and the higher the degree of myopia, the more obvious this situation is. The cause of myopia is generally considered to be a change in the refractive power of the eye, such as exceeding the normal refractive range, so that objects formed by external light fall in front of the retina, which causes the eye to be unable to see clearly. In order to correct this state, a concave lens needs to be placed in front of the eye, so that the object formed by external light falls back on the surface of the retina, and in this way myopia can be corrected, which is also the principle of frame glasses to correct myopia.