The lenses of the eye are divided into three types: concave lenses, convex lenses, and cylindrical lenses. Like concave lenses are glasses for myopic eyes, concave lenses are a kind of lens, light through the concave lens will diverge, and then through the refractive system of the human eye imaging on the retina, into a small real image, so wear concave lenses to see things will become smaller, the higher the degree of myopia of the human eye, the greater the degree of concave lenses, see things will become smaller and smaller. And like presbyopia wear glasses lenses, which is convex lens, convex lens is will make the light convergence, and then through the refraction system of the human eye, will be a magnified image, imaging on the retina. So like presbyopia will need to wear convex lenses, if the higher the degree of presbyopia, the higher the degree of convex lenses will be.