(1) PRK (excimer laser refractive keratectomy): the principle is to scrape the corneal epithelium and then apply the excimer laser to cut the anterior elastic and superficial stromal layers of the cornea, the curvature of the cornea is reduced after cutting, and the refractive power of the cornea is lowered, thus correcting myopia. The advantage is that the operation is simple, but the disadvantage is that the vision recovery is slow, the hormone medication time is long, and there are more complications. (2) LASEK (excimer laser subepithelial keratomileusis): the principle is to make a corneal epithelial flap first, and then apply the excimer laser to cut the anterior elastic lamina and superficial stroma layer of the cornea, the curvature of the cornea is reduced after the cutting, and the refractive power of the cornea is reduced, so as to correct the myopia. lasek is a kind of surgery between prk and lasik, which is suitable for the cornea is thin and the curvature is high, LASEK is a procedure between PRK and LASIK, and is suitable for patients with thin corneas, high curvature, and low-to-moderate myopia in small eyes with small eyelids. (3) LASIK (excimer laser in situ keratomileusis): the principle is to use microkeratome or femtosecond laser to form a corneal flap first, and then use the laser to cut the corneal stroma layer, and after the cutting is completed, the cut corneal flap is restored to its original position. The curvature of the cornea is reduced after cutting and the refractive power of the cornea is reduced, thus correcting myopia. The advantages are fast vision recovery and short hormone medication time, but the technical requirements for doctors are higher than PRK and LASEK. (4) Epi-LASIK (subepithelial – excimer laser in situ keratomileusis): its principle is to use microkeratome to form a corneal epithelial flap first, and then laser cutting corneal stroma layer under the corneal epithelial flap, the cutting is completed, and the cut flap will be restored to its original position. After cutting, the curvature of the cornea is reduced and the refractive power of the cornea is lowered, thus correcting myopia. The advantage is that it has some of the advantages of LASEK and LASIK, but it is still in fact a superficial surgery with the main disadvantages of superficial surgery.