The reason is that after myopia is formed, the front and rear axes of the eyes will become longer, that is, the eyeballs will gradually become rectangular and look like convex eyes from the outside. Once formed, it cannot be changed. The principle of excimer therapy for myopia is to change the refractive state by cutting the cornea. To put it bluntly, glasses are polished on the cornea (the front of the eye wall). The two are not the same.