The normal human cornea is transparent and non-vascular, and is an important component of the refractive system of the eye, accounting for 3/4 of the total refractive power of the eye, and is also the surgical site for excimer laser keratomileusis. The cornea is mildly transverse oval in appearance, with a transverse diameter of about 11.5-12 mm and a vertical diameter of about 10.5-11 mm, slightly protruding forward. The peripheral thickness of the cornea is about 1mm, and the central part is the thinnest at about 543±67.9um. Excimer laser refractive corneal surgery is performed by cutting the cornea to change its refractive power, and the postoperative corneal thickness will become thinner and weaker. Therefore, a certain amount of corneal thickness is decisive for the choice of surgery, the design of the size of the cut, and the calculation of the safe thickness retention of the corneal stroma. Precise corneal thickness measurements should be done prior to surgery to determine if the cornea is of sufficient thickness for keratoconus surgery. Since the thinnest part of the cornea and the deepest part of the cornea for myopic laser ablation are generally in the central corneal region, preoperative central thickness measurement should be of utmost importance. A thin cornea may indicate an early cone cornea; the central peripheral corneal thickness, especially when thinning inferiorly, should exclude the possibility of an early cone cornea. People with cone corneas are not good candidates for laser refractive corneal surgery. In order to ensure that the cornea has a certain strength of resistance after laser surgery and to avoid as much as possible the secondary cone corneas caused by surgery, the state has set a series of standards for excimer laser keratomileusis: central corneal thickness below 480um (some experts recommend below 500um) is not an option for LASIK surgery; central corneal thickness below 460um (some experts recommend below 470um ) are not suitable for any kind of laser surgery. The postoperative corneal stromal bed thickness should not be less than 250 um. The total amount of laser cutting should not exceed 50% of the corneal thickness. Post-LASIK conical cornea is one of the most serious complications of LASIK surgery with an incidence of 0.04-0.6%. The risk factors are: dilated corneal disease; stuttering cone corneas; residual corneal stromal bed thickness too thin; thin preoperative corneas; young people; high myopia, etc. Since thin corneas are more likely to develop cone corneas, is the thicker the cornea, the better it is? The answer is no. If the central cornea is significantly thickened, especially when the thickness exceeds 600um, it should be ruled out that it is due to corneal endothelial dysfunction, such as Fuchs dystrophy, and corneal endothelioscopy is also required. Therefore, the thicker the cornea is not the better.