Eye surgeries to correct vision have concentrated on changing the curvature of the cornea.
Refractive power is both a function of curvature and the change in refractive index.
Surgeries that change the curvature of the cornea by removing tissue from the outside of the cornea generally cause scarring. To avoid scarring, surgery can be performed inside the cornea. First, a half thickness flap of cornea is cut using a mechanical blade. Then, the flap is pulled back. An eximer laser then removes tissue from the exposed region creating the refractive change.