Before answering your question, you should first understand a concept-diopter: when light from an object shoots into another substance with different density, the propagation direction of light is deflected. This phenomenon is called refraction, and the unit that indicates the size (refractive power) of this refractive phenomenon is diopter (abbreviated as "D").

Myopia is caused by ametropia, and the degree of glasses refers to diopter. The degree of myopia we usually say refers to 100 times of diopter. For example, if you can see 1.2 vision, you certainly don't need to wear eyes.

This is the calculation formula: d =100/f.

F is the focal length unit m of glasses.

D is the degree of glasses.