Any clouding of the lens caused by congenital or acquired factors is called a cataract. Because of the different locations and degrees of lens clouding, there will be some differences in the clinical presentation of patients. In the early stage of cataract, if the clouding is at the edge of the lens and the degree is relatively mild, so it may have no effect on vision and many patients do not have any clinical manifestations in the early stage. If the clouding foci are in the visual center, even if the degree is mild, symptoms will appear, especially if the clouding gradually worsens, or if posterior subcapsular or nuclear clouding appears, the symptoms will be significantly aggravated. Some patients may feel that their eyes are easily fatigued in the early stage, and they may experience loss of vision in the sun, or they may easily experience visual distortion, glare, or monocular diplopia or monocular hyperopia; in case of nuclear cataract, because of the increase of nuclear refractive index, it may easily cause nuclear myopia, so these patients may feel that their vision suddenly improves and they do not need the presbyopic glasses they used to use. Currently, for cataract patients, there is no medication and surgery is considered. The mainstream surgical procedure is cataract ultrasound emulsion extraction plus IOL implantation.