The lens is a biconvex, elastic, avascular, transparent tissue with a complex metabolic process, and changes in its transparency and position can produce severe visual impairment. The lens is an important component of the refractive media of the eye, equivalent to a 1900 degree convex lens, with unique light transmission and refraction, and can filter some ultraviolet light and protect the retina and macula. The suspensory ligament of the lens and ciliary muscle can complete the regulation function of the eye. By the age of 40 and above, the elasticity of the lens decreases and presbyopia will occur.