If a contact lens has a defective edge, it is not recommended to wear it again. Continued use may affect eye comfort and vision, and also cause damage to the eye, commonly such as scratching the cornea or leading to infection, patients should be replaced with new glasses under the guidance of a doctor.1. Scratching the cornea: Contact lenses are smooth and soft in texture and do not damage the cornea. When its edges are defective, the defective parts are prone to produce sharp tips, which in mild cases lead to scratching of the conjunctival and corneal tissues, and in serious cases lead to damage to the corneal epithelium and stromal layer, which in turn affects vision; 2, leading to infection: wearing contact lenses themselves will make the oxygen permeability of the eye surface decrease, affecting metabolism and easily reducing the resistance of the cornea. Improper care or incomplete disinfection can easily lead to eye tissue infections, such as conjunctivitis and keratitis. At this time, if you wear contact lenses with one point missing from the edge of the eye, if you accidentally scratch the cornea or eye tissue, it will increase the probability of infection, causing redness and pain, fear of light and tears, vision loss and other uncomfortable symptoms. Therefore, contact lenses with a little missing edge are recommended to be replaced with new contact lenses according to the optometry results. In addition, when wearing contact lenses, patients need to be careful not to wear them for more than 8 hours a day, and to pay attention to disinfection to prevent bacteria from growing and causing infection.