This is a procedure where the cornea is sculpted with a laser in order to fix refractive error and decrease reliance on glasses. The cornea is the clear window that makes up the front of your eye. Surprisingly, the corneal surface does the majority of the light-focusing of the eye (not the lens inside the eye like you might expect). People with flat corneas have “weaker” powered eyes (hyperopia or farsightedness) while people with steep corneas have “over-powered” eyes (myopia or nearsightedness). With LASIK, a special excimer laser is used to obliterate tissue and sculpt the cornea into the correct steepness. To minimize pain and inflammation, the laser is not applied directly to the surface of the eye. Instead, a partial thickness cut is made in the cornea to create a “flap.” This flap is opened like a trapdoor to expose deeper layers of the corneal stroma underneath. The laser is then applied to this area to remove corneal tissue. When done, the corneal flap is flipped back over and “squeegeed” back into place to heal. While this may seem unnecessarily complicated, this flap method decreases inflammation and speeds healing time because the surface corneal epithelium is relatively intact. Because the treatment area is deep in the corneal tissue, it is more protected from problems (like scarring) while healing. There have been some more recent advances in the LASIK procedure … one is Intralase where a femtosecond laser is used to create the flap (instead of the original microkeratome blade of the past). Not everyone is a good candidate for LASIK, such as those with keratoconus or naturally thin corneas (as measured by pachymetry). PRK is a similar to LASIK, but the laser is applied directly to the surface of the eye and thus has more post-operative discomfort and more potential for corneal haze (scaring).