The new glasses are curved, i.e. straight and curved, usually due to the following reasons: 1, the new glasses are spherical lenses, spherical lenses are cheap, but the peripheral part of the lens will produce a significant phase difference, resulting in distortion and deformation. 2, because the new glasses are significantly higher than the original degree, due to the lens correction of myopia or astigmatism, will be refracted to the external The higher the degree of refraction, the more likely the deformation, but usually more than half a month of continuous wear will be able to gradually get used to and adapt to. 3, is due to the new glasses lens area is too large, the lens area is larger, usually make the patient’s field of vision is wider, but the lens peripheral parts of the formation of the phase difference, significantly higher than the central part of the formation of the phase difference, will make the patient appear to be curved. The difference between the peripheral part of the lens and the central part of the lens is significantly higher than the difference between the peripheral part of the lens and the central part of the lens.