Senile cataracts are also known as age-related cataracts. It occurs mostly in middle-aged and older adults over the age of 50, whose lens becomes cloudy and blurred vision occurs. Its incidence increases with age. By the age of 80 or older, 100% of the population is cataract-prone. Cataracts often occur in both eyes and can develop sequentially. Patients often feel shadows in front of their eyes, blurred vision, and gradual loss of vision. Some patients have monocular diplopia, hyperopia, and iris vision. According to the beginning of lens clouding, cataract can be divided into three types: cortical, nuclear, and posterior subcapsular. Cataracts are divided into four stages: initial, distended, mature, and overmature stages. Surgery is still the main treatment for cataracts. When is the most appropriate time to have surgery? Nowadays, cataract extraction plus IOL implantation is mostly used, which is done at one time. Since the surgery is performed under a microscope and the advanced ultrasound emulsifier is used, the surgery has the advantages of small incision, high precision, short operation time, less patient pain and good vision correction. In principle, surgery can be performed when the corrected visual acuity is below 0.3 or even 0.5. However, if the cataract affects life and work, it can be done regardless of the amount of vision.