laser-based eye (eye, human) surgery commonly used to correct nearsightedness ( myopia), farsightedness ( hyperopia), and astigmatism. LASIK eye surgery was developed in the early 1990s, when ophthalmologists combined the technique of keratomileusis, in which the cornea is removed, frozen, reshaped, and replaced, with the technique of photorefractive keratectomy (PRK), in which a laser is used to reshape the cornea. In the LASIK procedure a hinged flap is made in the outer corneal tissue (the transparent layer covering the front of the eye) and lifted out of the way to allow an excimer laser (an ultraviolet chemical laser, also called an exciplex laser) to reshape the underlying tissue. Tissue reshaping improves the eye's ability to focus light and thus relieves blurred vision and reduces dependency on eyeglasses or contact lenses (contact lens). The natural adherence properties of the replaced corneal flap negate the need for stitches. LASIK surgery is often preferred to photorefractive keratectomy.