Lasik is an anagram for Laser Assisted In-situ Keratomileusis. This operation is performed by precisely fashioning a flap of corneal tissue. This flap is then folded back to expose the underlying corneal stroma. Excimer laser treatment is then applied to the exposed corneal stroma to alter its shape in a pre-determined way. This change in the shape of the tissue alters its focusing power thereby correcting the refractive error of the eye being treated.

When the eye is being treated with the Excimer laser the eyelids are kept open with a small spring which is known as a speculum. Local anaesthetic drops are used to numb the eye prior to the surgery. The flap can be fashioned in a very precise manner either with a Microkeratome or else with a laser that delaminates the corneal tissue. This type of laser is known as a Femtosecond laser.

Once the corneal stroma has been treated with the Excimer laser beam the flap of corneal tissue is then replaced with the surface layers of the cornea intact.