LASEK and PRK are another commonly used method for the treatment of refractive errors and astigmatism, myopia (nearsightedness), and hyperopia (farsightedness) all over the world; the most important difference between these methods with LASIK is the location of excimer radiation on the cornea. In LASIK, after peeling the surface of the cornea, the laser radiation reaches the new layer and peeling is carried out, while in LASEK surgery, without peeling the cornea and just after removing the corneal epithelium, which is the outermost layer of the cornea layer, the laser radiation reaches the cornea surface. On the other hand, LASEK surgery is introduced as the modified type of PRK surgery; nevertheless, it is less popular than the PRK method. In the PRK (Photorefractive Keratectomy) method, the patient's degree of nearsightedness is reduced using excimer laser radiation. By this method, a very thin layer of the cornea, at a rate of a few tens of microns is removed; and the rate of refractive errors in the eye is reduced by applying changes to the corneal curvature.