Cataract patients once lost their vision and suffered the pain of “darkness”. When the cataract is removed, the patient can see again, but some patients worry whether the cataract will grow after it is removed. When the lens is cloudy, it is called a cataract. It is a biconvex transparent tissue, and when the lens is cut open and observed with a microscope, a membrane called the lens capsule can be seen on the surface of the lens. The fibers located in the core are called the nucleus of the lens, and the fibers located in the superficial layer of the lens cortex. Immediately under the anterior capsule, a layer of cells called the lens epithelium is laid down, and there are no epithelial cells under the posterior capsule. Knowing the anatomy of the lens, it is easy to understand that if the entire lens capsule wrapped cataract is removed, it is impossible to grow again after surgery. However, with the development of modern medical science and technology, the current cataract ultrasound emulsification and cataract extracapsular extraction in ophthalmology need to keep the posterior capsule membrane of the lens intact so that the implanted posterior chamber IOL can be placed in the capsule bag; conversely, if there is no posterior capsule membrane, it is also impossible to implant a posterior chamber IOL; if the entire lens is not completely removed, it is also possible to grow cataract again. After the current advanced ophthalmic blade-free femtosecond cataract surgery or microincision cataract ultrasound emulsification with folding IOL implantation, not only the complete posterior capsule but also part of the anterior capsule is preserved in the eye. If the epithelial cells under the anterior capsule membrane continue to proliferate and produce new lens fibers, which attach to the posterior capsule, the new lens fibers are not neatly shaped and arranged, and therefore also opaque, just like a thick layer of dust and dirt on the bright glass window again; it becomes posterior capsule membrane confusion turbidity, also called posterior cataract. According to the relevant literature, the incidence of posterior cataract is 20%~50% after ultrasonic emulsion extracapsular extraction, and it obviously affects the vision. Posterior cataracts obscure the pupil area and affect vision, and another capsulotomy must be performed to improve vision. For thicker proliferative membranes, the pupillary area can be cut or stabbed with a capsule, and if necessary, a hole of about 4 mm in diameter can be cut out in the pupillary area with scissors to ensure that light from the optic axis area enters the retina. For thinner proliferating membranes, YAG laser treatment is now mostly used. This laser is easy to operate and can be treated on an outpatient basis; the energy is easily controlled, the patient is painless, there are few complications, and most cases of posterior cataract recover after one treatment, making it a better method for treating posterior cataract. Therefore, if a patient with cataract feels a gradual loss of vision after surgery and is diagnosed with posterior cataract, a bright window can be reopened with the laser.