Excimer laser surgery” is generally referred to as “excimer laser refractive corneal surgery”, which mainly includes four types of procedures: 1. Excimer laser surface keratomileusis (PRK), which is the earliest method used in clinical practice. Currently, PRK is considered safe and effective for the treatment of low to moderate myopia, hyperopia and astigmatism, but it is now less commonly used due to postoperative pain, refractive regression and other complications. 2. Excimer laser in situ keratomileusis (LASIK), which is the mainstream procedure at present. It is a stromal layer cutting under the corneal flap, keeping the corneal epithelium and anterior elastic layer intact, which can avoid most of the complications of PRK. It is characterized by a broadened range of myopia correction, painless intraoperative and postoperative period, fast vision recovery, and no corneal opacities left behind. During the procedure, a thin corneal flap with a tip is cut out of the cornea with a microknife, the flap is lifted, laser cutting is performed under the flap, and the flap is then returned to its original position. This can be used for low, intermediate, and high myopia, but LASIK also has defects associated with the flap, namely corneal folds, displacement, subclavian epithelial implantation, astigmatism, and excessive cutting, resulting in corneal dilation and cone corneas. The use of LASIK is also limited for patients with high and relatively thin corneas relative to myopia, but for highly myopic patients with sufficiently thick corneal flaps, LASIK is still preferred. 3, Excimer laser subepithelial in situ keratomileusis (LASEK), is a modified form of PRK surgery. LASEK is a modified version of PRK surgery, in which a laser or low-concentration alcohol is used to soak the surgical area of the cornea and make a corneal epithelial flap, and the laser cuts the tissue under the flap. LASEK does not have the complications of LASIK for corneal flap, shortens the healing time of corneal epithelium after PRK surgery, reduces the pain reaction and the degree of corneal clouding (haze), but the corneal epithelial flap breaks and edema during surgery are the same as PRK, and the recovery of vision and refractive stability after surgery is slower than LASIK. Therefore, it is mainly suitable for patients with thin corneas, occupational characteristics prone to ocular trauma resulting in corneal flap dislocation or other patients who are not suitable for LASIK. 4. Ioannis, a Greek physician, was also the first to propose Epi-LASIK. It is believed that Epi-LASIK can combine the advantages of LASEK and LASIK surgery, and better avoid the shortcomings of both, it uses a rotating epithelial knife to “make an active epithelial flap” in the corneal epithelium with a thickness of only 50 μm or so, instead of using alcohol immersion as in LASEK surgery, in order to The thickness of the flap is only about 50μm, instead of soaking it in alcohol as in LASEK surgery, so as to “save” the maximum thickness of the cornea, the postoperative irritation symptoms are minimal, the chance of corneal clouding (Haze) is less than in PRK, and the incidence of myopic regression is low.