ADAM Health Encyclopedia

LASIK eye surgery

Definition

LASIK is eye surgery that permanently changes the shape of the cornea (the clear covering on the front of the eye) in order to improve vision and reduce a person's dependency on glasses or contact lenses.

See also: Corneal surgery

Alternative Names

Laser-Assisted In Situ Keratomileusis; Laser vision correction

Description

For clear vision, the eye's cornea and lens must bend (refract) light rays properly, so that images are focused on the retina. If the light rays aren't clearly focused on the retina, the images you see are blurry.

This blurriness is referred to as a "refractive error." It is caused by an imperfectly shaped eyeball, cornea, or lens. LASIK uses an Excimer Laser (an ultraviolet laser) to precisely remove corneal tissue to correct the shape for better focusing.

A complete eye examination will be done before surgery to make sure your eyes are healthy. Other tests will be done to measure the curve of the cornea, the size and position of the pupils, the shape of the eyes (to make sure LASIK is an option), and the thickness of the cornea (to make sure you will have enough cornea tissue left after surgery).

A signed informed consent form is needed before the procedure, confirming knowledge of the risks, benefits, alternative options, and possible complications.

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

The only anesthetic used is an eye drop that numbs the surface of the eye. The procedure is done with the person awake. LASIK may be done on one or both eyes during the same session.

During LASIK, a special knife (a microkeratome) is used to cut a hinged flap of corneal tissue off the outer layer of the eyeball. The flap is lifted out of the way and a special laser is used to reshape the underlying corneal tissue.

The calculation for how much tissue is removed by the laser is done ahead of time. Once the reshaping is done, the surgeon replaces and secures the flap. No stitches are needed. An eye shield or patch will be placed over the eye to protect the flap and to help prevent rubbing or pressure on the eye until it has had enough time to heal.

Risks

The long-term effects of LASIK past 5 years after the surgery are yet to be determined.

Over- or under-treatment of the condition may occur, requiring additional surgery, contact lens, or glasses.

Risks may include:

• Corneal infection
• Corneal scarring or permanent problems with the cornea's shape, making it impossible to wear contact lenses
• Decreased distance vision at high altitudes
• Decrease in contrast sensitivity --even with 20/20 vision, objects may appear fuzzy or gray
• Dry eyes
• Glare or haloes
• Light sensitivity
• Night driving problems
• Patches of red or pink in the white of the eye
• Reduced vision or permanent vision loss
• Scratchiness

Some patients, although they may see much better than before LASIK without glasses, will still need glasses for their best vision.