Laser In Situ Keratomileusis (LASIK), a form of outpatient corneal surgery, combines incisional and laser surgery to improve myopia (nearsightedness), hyperopia (farsightedness), astigmatism and presbyopia.
Once the surgeon has conducted all pre-operative examinations, the eye is anesthetized with numbing eyedrops, the area around the eye is cleaned, and an instrument called a lid speculum is used to hold the eyelids open. The surgeon will then use a specialized instrument, called a microkeratome, to cut a thin, circular flap – the outermost 20 percent of the thickness of the cornea – to expose the portion beneath. This part of the procedure is called keratectomy.
While the inner cornea (the stroma) exposed, the surgeon will ask the patient to fixate on a specific light source above the patient. This is to ensure that the laser beam is aligned precisely with the center of the patient’s eye. Once the eye is in the correct position, the laser treatment is performed. The computer-controlled excimer laser removes the tissue under the flap and reshapes the cornea of the eye. In less than 60 seconds, ultraviolet light and high-energy pulses from the excimer laser reshape the internal cornea with accuracy up to 0.25 microns, or 1/4000 of a millimeter.
After the pulses of laser energy vaporize the corneal tissue, the flap is put back into its original position. The surgeon will observe the eye for three to five minutes to ensure bonding. Because the cornea bonds quickly, healing is rapid, and the eye does not require stitches.
Results from LASIK are excellent with 95% of patients achieving 20/40 vision or better. The entire procedure takes only a few minutes. Improved vision is often possible on the day following the surgery. The vast majority of patients return to their daily activities the day following surgery. Eye drops and night protection are necessary for designated periods of time.