PRK utilizes a computer-guided excimer laser to precisely reshape the corneal surface and move the focal point closer to the retina. Unlike during LASIK, a flap is not made, but a very thin layer of the surface cornea (about the thickness of a hair) is removed. Excimer lasers emit a high energy beam that removes tissue by releasing molecular bonds. Since the process does not produce heat or cause burning, the excimer is considered a "cool" laser. For patients with certain corneal disorders or conditions, PRK is preferable to LASIK.