In PRK the epithelium (top layer of the cornea) is scraped off and then the laser treatment is applied. A contact lens is used as a bandage to decrease discomfort. The epithelium then grows back over ...

In PRK the epithelium (top layer of the cornea) is scraped off and
then the laser treatment is applied. A contact lens is used as a
bandage to decrease discomfort. The epithelium then grows back over
the bare area during the next few days.

In LASEK the epithelium
is exposed to 20% alcohol which helps separate epithelium from the
cornea. The epithelium is pushed to one side and laser treatment
applied. The epithelial layer is replaced back onto the eye and held
in place with a contact lens. The contact lens is then removed a few
days later. LASEK is hence a no knife/flap operation.

Epi-Lasik
is a similar procedure that uses a keratome like that used for
Lasik, but engineered to only separate the epithelium. The
epithelium is left on a hinge, laser treatment applied and flap
replaced.