It employs excimer laser to ablate outer layer of cornea, epithelium, as well its connective tissue, stroma, to correct eye optical power. Laser Assisted Sub-Epithelium Keratomileusis (LASEK) is a procedure that also changes the shape of the cornea using an excimer laser to ablate the tissue from the corneal stroma, under the corneal epithelium, which is kept mostly intact to act as a natural bandage. The surgeon uses an alcohol solution to loosen then lift a thin layer of the epithelium with a trephine blade (usually with a thickness of 50 micrometres).[5] During the weeks following LASEK, the epithelium heals, leaving no permanent flap in the cornea.