LASIK is an acronym for laser-assisted in-situ keratomileusis—a type of laser eye surgery that permanently reshapes the cornea to correct refractive errors.
Normally, the cornea—the clear layer in the front of the eye—focuses light directly on the retina in the back of the eye. When the cornea is irregularly shaped, light doesn't focus precisely on the retina, which results in these refractive errors:
- Nearsightedness (myopia)—clear, close vision but blurry distance vision that occurs when the cornea is more curved than normal, resulting in light rays focusing in front of the retina.
- Farsightedness (hyperopia)—clear distance vision but blurry close vision that occurs when the cornea is too flat, and light focuses behind the retina.
- Astigmatism—blurred vision due to an irregularly shaped cornea.
Who is a Good Candidate for LASIK?
LASIK is FDA-approved for people aged 18 and older who've had a stable eyeglass or contact lens prescription for at least two years in a row, and whose eyes are generally healthy. Certain people may not be good candidates for this procedure, including those who have:
- an eye infection or injury
- very thin corneas
- dense cataracts
- severe dry eyes
- uncontrolled diabetes
- a very high refractive error, such as severe nearsightedness
What to Expect
Before the LASIK procedure, the eye surgeon will do an exam to check the shape and thickness of the cornea, look for refractive errors, and take detailed measurements of the eye. Some eye surgeons use newer wavefront- and topography-guided technologies to create a custom map of the cornea, which results in more precise vision correction.
During the procedure, the eye is first numbed using special eyedrops. The surgeon uses a femtosecond laser or blade called a microkeratome to cut a thin flap of tissue from the front of the eye. The doctor then pulls back the flap to reveal the cornea.
Then a laser burns away small amounts of tissue to reshape the cornea so that it focuses light more directly on the retina. There shouldn't be any pain, although some people feel pressure during the procedure. The entire LASIK surgery takes about 15 minutes for both eyes.
After the procedure is completed, the surgeon places the flap back. It will seal on its own, without stitches, in the days following the procedure.
LASIK Benefits and Risks
Today, doctors perform about 600,000 LASIK surgeries annually in the United States. Most people who have this surgery achieve 20/20 vision, which means they can see from 20 feet away, which is what people with normal vision can see at that distance without having to wear glasses or contact lenses. More than 95% of people who've had this procedure say they are pleased with the results.
LASIK can cause side effects, however. Most are mild, such as dry eye, itching, and burning, which affects 20% to 40% of people who have the procedure. Also relatively common are glare and halos around lights at night. These symptoms typically last for a month or two after the procedure, but some people who've had LASIK will continue to have symptoms long-term.
In a small number of cases, LASIK doesn't completely correct vision. In these cases, people will still need to rely on glasses or contact lenses for clear vision after their surgery. Those who don't achieve full vision correction can return to their doctor for an additional procedure. Rarely, people who've had LASIK can lose vision due to infection, scarring, or poor healing.
Another drawback to LASIK is its cost, which is $2,200 per eye, on average. Health insurance typically won't cover the cost.
Image: DavidKevitch/Getty Images
About the Author
Stephanie Watson, Former Executive Editor, Harvard Women's Health Watch
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