LASIK (laser-assisted in situ keratomileusis) is an outpatient refractive surgery procedure used to treat nearsightedness, farsightedness and astigmatism. A laser is used to reshape the cornea — the clear, round dome at the front of the eye — to improve the way the eye focuses light rays onto the retina at the back of the eye.

With LASIK, an ophthalmologist (Eye M.D.) creates a thin flap in the cornea using either a blade or a laser. The surgeon folds back the flap and precisely removes a very specific amount of corneal tissue under the flap using an excimer laser. The flap is then laid back into its original position where it heals in place.

For people who are nearsighted, LASIK is used to flatten a cornea that is too steep. Farsighted people will have LASIK to achieve a steeper cornea. LASIK can also correct astigmatism by shaping an irregular cornea into a more normal shape.

It is important that anyone considering LASIK have realistic expectations. LASIK allows people to perform most of their everyday tasks without corrective lenses. However, people looking for perfect vision without glasses or contacts run the risk of being disappointed. More than 90 percent of people who have LASIK achieve somewhere between 20/20 and 20/40 vision without glasses or contact lenses. If sharp, detailed 20/20 vision is essential for your job or leisure activities, consider whether 20/40 vision would be good enough for you.

You should be comfortable with the possibility that you may need a second surgery (called a retreatment or enhancement) or that you might need to wear glasses for certain activities, such as reading or driving at night. Also, you should be aware that LASIK cannot correct presbyopia, the age-related loss of close-up focusing power.

How the LASIK procedure works

LASIK is performed while the patient reclines under a surgical device called an excimer laser in an outpatient surgical suite.

First, the eye is numbed with a few drops of topical anesthetic. An eyelid holder is placed between the eyelids to keep them open and prevent the patient from blinking. A suction ring placed on the eye lifts and flattens the cornea and helps keep the eye from moving. The patient may feel pressure from the eyelid holder and suction ring, similar to a finger pressed firmly on the eyelid.

From the time the suction ring is put on the eye until it is removed, vision appears dim or goes black. Once the cornea is flattened, a hinged flap of corneal tissue is created using an automated microsurgical device, either a laser or blade. This corneal flap is lifted and folded back. Then the excimer laser preprogrammed with the patient's unique eye measurements is centered above the eye.

The surgeon checks that the laser is positioned correctly. The patient looks at a special pinpoint light, called a fixation or target light, while the excimer laser sculpts the corneal tissue. Then the surgeon places the flap back into position and smoothes the edges. The corneal flap sticks to the underlying corneal tissue within two to five minutes, and stitches are not needed.

A LASIK surgery procedure
A LASIK surgery procedure

The patient should plan to have someone drive him or her home after the procedure and then take a nap or just relax. To help protect the cornea as it heals, the surgeon may place a transparent shield over the eye(s) to protect against accidental bumps and to remind the patient not to rub the eye(s). The patient may need to wear the shield only when sleeping. The surgeon will provide eyedrops to help the eye heal and relieve dryness.

It may take three to six months after LASIK surgery for the improvements in a person's vision to fully stabilize and any side effects to go away.

LASIK risks and side effects

LASIK, like any surgery, has potential risks and complications that should be carefully considered. Since it was approved by the FDA in 1998, LASIK is has become a popular treatment in the United States and the overall complication rate is low. Infection and inflammation are possibilities, as with any surgical procedure, and usually can be cleared up with medications.

Problems with the corneal flap after surgery sometimes make further treatment necessary. There is a chance, though small, that vision will not be as good after the surgery as before, even with glasses or contacts.

Some people experience side effects after LASIK that usually disappear over time. These side effects may include hazy or blurry vision; difficulty with night vision and/or driving at night; scratchiness, dryness and other symptoms of the condition called "dry eye"; glare, halos or starbursts around lights; light sensitivity; discomfort or pain; or small pink or red patches on the white of the eye. In a small minority of patients, some of these effects may be permanent.

Sometimes a second surgery, called a retreatment or enhancement, may be needed to achieve the desired vision correction. This is more likely for people who were more nearsighted, farsighted, or had higher astigmatism before LASIK — those whose vision originally needed more intensive correction. Approximately 10.5 percent of LASIK patients in the United States require a retreatment.

Considering LASIK? Learn more

Before choosing to have LASIK, it's important to do your homework to ensure you are a good candidate, understand the potential risks and benefits, and have realistic expectations about what your vision will be like after surgery and for years to come. To ensure the best possible outcome, be a well-prepared and informed patient by reviewing the resources below before you have LASIK. If these materials raise any questions for you, be sure to discuss these questions with your Eye M.D.

Is LASIK For Me? A Patient's Guide to Refractive Surgery (PDF 303K)
This guide, produced by the American Academy of Ophthalmology, offers straight-forward facts about what makes a good LASIK candidate, the risks and benefits of the surgery, how to choose a surgeon and an introduction to the informed consent process.

LASIK Surgery: Why All Patients Need the K Card (PDF 650K)
If you have decide to have LASIK, it is important to keep a record of your pre-operation and post-operation eye information. Your Eye M.D. may need this information if you have other eye surgery later, such as cataract surgery. Bring this "K Card" with you to your Eye M.D. appointment to have it completed and keep it for future use.

Questions to Ask When Considering LASIK
If you are considering LASIK, you should discuss with your Eye M.D. the benefits and risks — including quality of life issues — that could result from correcting vision with surgery rather than eyeglasses or contact lenses.

Next Page: Alternative Refractive Surgery Procedures

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