Pre-operative:-
Patients wearing contact lenses are typically instructed to stop wearing them approximately 7 to 10 days prior to surgery. Prior to the surgery, the surfaces of the patient's corneas are examined with a computer-controlled scanning device to determine their exact shape. Using low-power lasers, it creates a topographic map of the cornea. This process also detects astigmatism and other irregularities in the shape of the cornea. Using this information, the surgeon calculates the amount and locations of corneal tissue to be removed during the operation. The patient is typically prescribed an antibiotic to start taking beforehand, to minimize the risk of infection after the procedure.

The operation:-
The operation is performed with the patient awake and functional, however, the patient is typically given a mild sedative (such as Valium or diazepam) and anesthetic eye drops. The surgeon operates the lasers, which make all of the incisions. A computer system tracks the patient's eye position 4,000 times per second, redirecting laser pulses for precise placement. A flap is cut in the cornea using a blade (called a microkeratome) or a femtosecond laser. A hinge is left at one end of this flap. The flap is folded back revealing the stroma, the middle section of the cornea.

Then an excimer laser (193 nm) is used to remodel the corneal stroma. The laser vaporizes tissue without causing damage to adjacent stroma in a finely controlled manner. The layers of tissue removed are tens of micrometres wide.

All text is available under the terms of the GNU Free Documentation License (see Copyrights for details).