LASIK, LAY zihk or LAY sihk, surgery is a medical procedure used to correct certain eye defects that cause imperfect vision. LASIK stands for laser-assisted in situ keratomileusis. Eye defects called refractive errors prevent the eye from properly focusing light to create images. These defects include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. People who undergo LASIK surgery can reduce or even eliminate dependency on eyeglasses or contact lenses.