Keratomileusis is the surgical improvement of the refractive state of the cornea performed by lifting up the front surface of the eye by forming a thin hinged flap under which the shape of the cornea is changed by using an excimer laser or other surgical device. A microkeratome is usually used to cut the flap, but a femtosecond laser can also be used to make the flap. Before the advent of the excimer laser, keratomileusis was performed using a cryolathe, which froze thin flaps of corneal tissue and lathe cut them much like one cuts the lens of a pair of glasses. After thawing, these reshaped flaps were placed under the front flap to correct visual improvement. LASIK is currently the only commonly performed keratomileusis procedure.