In both procedures, a specially-trained ophthalmologist uses the computer-guided excimer laser to gently remove a thin layer of tissue from the cornea to achieve a desired correction. Prior to the procedures, drops are placed in the eye to numb it (similar to what an eye doctor uses to check eye pressure for a glaucoma test) and an instrument called a speculum is placed in the eye to prevent the patient from blinking. In PRK, the surgeon first removes the surface cells of the cornea using the laser before sculpting the underlying tissue, and then surface cells regenerate over the next 48 to 72 hours under a bandage contact lens. No needles are used, and the patient does not normally experiences any pain. In LASIK, a femtosecond laser is used to separate a thin layer of the corneal tissue, which is left attached on a hinge. The excimer laser is then used to sculpt tissue from the corneal bed and the flap is floated back into place, reattaching without the need for sutures.