The ciliary body regulates the refractive power of the lens, mainly by contraction of the ciliary muscle. The ciliary body is connected to the equatorial part of the lens by a large number of slender suspensory ligaments. When the ciliary muscle contracts, the suspensory ligaments are relaxed, and the lens itself is a structure like a convex lens, which itself has a certain degree of elasticity, and when the suspensory ligaments are relaxed, the lens becomes more convex with its own elasticity, and then the refractive power increases accordingly and the focal length becomes shorter, making the refractive power of the whole eye increase When the ciliary muscle is relaxed, the refractive power increases and the focal length becomes shorter, allowing the eye to see clearly. When the ciliary muscle relaxes, the suspensory ligament will tighten and flatten, and the lens, which was like a convex lens, will become slightly flattened, and the refractive power will be reduced accordingly, so that the refractive power of the whole eye will be reduced, and it will be possible to see things clearly at a distance.