Light entering the eye is focused partly by the cornea, the clear front surface. LASIK changes that surface’s curvature by removing a carefully planned amount of corneal tissue with an excimer laser. The aim is to reduce a refractive error such as nearsightedness.
Reshaping the cornea
In a typical LASIK procedure, a thin corneal flap is made and lifted before the underlying tissue is reshaped. The flap is then repositioned. The pattern of removal depends on measurements of the eye, and the cornea must be suitable for the operation. The laser changes anatomy; it does not replace the retina or the brain’s role in vision.
Limits and risks
Not everyone is a candidate. Dry eye, glare, halos, incomplete correction, and other complications are possible, and the need for glasses later is not eliminated for everyone. An eye specialist reviews the individual measurements and alternatives. Optical coherence tomography is another light-based technology used to image tissue, but it measures rather than reshapes it.
Related: how optical coherence tomography builds depth images.