LASIK is eye surgery that permanently changes the shape of the cornea (the clear covering on the front of the eye). It is done to improve vision and reduce a person’s need for glasses or contact lenses.

For clear vision, the eye’s cornea and lens must bend (refract) light rays properly. This allows images to be focused on the retina. Otherwise, the images will be blurry.

This blurriness is referred to as a “refractive error.” It is caused by a mismatch between the shape of the cornea (curvature) and the length of the eye.


LASIK uses an excimer laser (an ultraviolet laser) to remove a thin layer of corneal tissue. This gives the cornea a new shape so that light rays are focused clearly on the retina. LASIK causes the cornea to be thinner.

LASIK is an outpatient surgical procedure. It will take 10 to 15 minutes to perform for each eye.

The only anesthetic used is eye drops that numb the surface of the eye. The procedure is done when you are awake, but you will get medicine to help you relax. LASIK may be done on one or both eyes during the same session.

To do the procedure, a flap of corneal tissue is created. This flap is then peeled back so that the excimer laser can reshape the corneal tissue underneath. A hinge on the flap prevents it from being completely separated from the cornea.

When LASIK was first done, a special automated knife (a microkeratome) was used to cut the flap. Now, a more common and safer method is to use a different type of laser (femtosecond) to create the corneal flap.
The amount of corneal tissue the laser will remove is calculated ahead of time.

The surgeon will calculate this based on several factors including:

• Your glasses or contact lens prescription

• A wavefront test, which measures how light travels through your eye

• The shape of your cornea surface

Once the reshaping is done, the surgeon replaces and secures the flap. No stitches are needed. The cornea will naturally hold the flap in place.