Since corneal contact lenses change the shape of the cornea, they should be discontinued prior to the examination and evaluation for excimer laser keratomileusis. Although there is no definitive conclusion on how long patients should stop wearing contact lenses, current clinical practice experience suggests that soft contact lenses should be discontinued for at least 3 days to 2 weeks, with an average of more than a week. Hard contact lenses (keratoplasty, RGP) should be discontinued for at least 3 weeks until the cornea has returned to its original shape and the examination results are stable. The extent to which corneal contact lenses (contact lenses) affect the shape of the cornea and the refractive error varies from person to person. The purpose of stopping wearing contact lenses prior to the examination is twofold: 1. to allow the cornea to fully recover its original shape so as not to affect the preoperative refractive error and thus the accuracy of the surgical correction. Different types of corneal contact lenses (different materials, different curvatures, matching degree with corneal shape) and corneal contact lenses affect different corneal tissues (such as thickness, texture, hardness, elasticity, etc.) to different degrees. Generally, corneas that are easily deformed can easily regain the shape they had before they were worn. However, this type of cornea should be the most attention, most of them are thin corneas or have the characteristics of cone corneas. 2, stop wearing contact lenses is to make the corneal epithelial cells to restore normal, especially the damaged corneal epithelial cells to recover, about 24-48 hours. If the contact lens leads to “keratitis”, it needs to be treated systematically, after the corneal inflammation is completely controlled, and only after the cure can be operated.