In optometry, you may hear some refractive errors, and you will see some eye degrees represented by symbols on the optometry list. In fact, these have a great relationship with the refraction. Our eyeball is a mirror with strong adjustment ability. However, if we do not pay attention to the habit of using our eyes, the adjustment ability of our eyes will also have problems, which will also involve diopter. Let's take a look at what diopter means. Diopter, or power, expressed in English with 'DioptreTo put it simply, when light is incident from one object to another material with different optical densities, the propagation direction of the light is deflected during the propagation of the light. This phenomenon is called refraction. The unit of refraction size or power is the diopter, abbreviated 'D'. 1D power is equivalent to focusing parallel light rays at a focal length of 1 meter. The function of the eye to refract light is called refraction, and the ability to refract light with optical power is called refraction. The degree in glasses represents the diopter. The value of the diopter D multiplied by 100 is the eye degree. For example, -1.0D is equal to 100 degrees of myopic glasses (concave lens). Generally, the power of a convex lens (such as a far-sighted lens) is a positive number (+), and the power of a concave lens (such as a myopic lens) is a negative number (-). So we can see that the digital representation on the prescription is represented by '+' or '-'. Convex lenses made of the same material, if the convexity is greater, the diopter will be larger, on the contrary, the smaller the convexity, the smaller the diopter. For the same eyeball, the higher the degree of myopia, the more prominent the eyeball will be. If the diopter of the eye is not normal, it will cause the image on the retina to be unclear. Generally speaking, it is corrected by wearing glasses, and the diopter of the eye is corrected by the lens, so as to achieve a clear image. Therefore, if the refractive error is correct, it is necessary to carry out scientific optometry to correct vision.