The LASIK Procedure:
A Complete Guide

By Liz Segre; reviewed by Charles Slonim, MD, and Brian S. Boxer Wachler, MD

LASIK is the most commonly performed refractive surgery procedure. You may hear people calling it "LASIX," but the correct name is LASIK, which is short for "laser-assisted in situ keratomileusis."

Why is it so popular? LASIK has advantages over other vision correction procedures, including a relative lack of pain afterward and the fact that good vision usually is achieved by the very next day.

An instrument called a microkeratome is used in LASIK eye surgery to create a thin, circular flap in the cornea. Another, newer way of making the flap is with a laser.

The surgeon folds the hinged flap back out of the way, then removes some corneal tissue underneath using an excimer laser. The excimer laser uses a cool ultraviolet light beam to precisely remove ("ablate") very tiny bits of tissue from the cornea to reshape it.

When the cornea is reshaped in the right way, it works better to focus light into the eye and onto the retina, providing clearer vision than before. The flap is then laid back in place, covering the area where the corneal tissue was removed.

Both nearsighted and farsighted people can benefit from the LASIK procedure. With nearsighted people, the goal is to flatten the too-steep cornea; with farsighted people, a steeper cornea is desired. Excimer lasers also can correct astigmatism by smoothing an irregular cornea into a more normal shape.

Before the LASIK Procedure

If you are considering LASIK eye surgery, your first step is to choose a LASIK surgeon.

To decide whether you're a good candidate for LASIK, your eye doctor will perform an eye exam to determine eye health, what kind of vision correction you need and how much laser ablation is required.

Your doctor also will look for signs of dry eye disease, which must be treated and cleared up before LASIK can be performed. Even if your eyes have a normal tear film, your eye surgeon as a precaution may recommend treatment to reduce your risk of developing dry eyes after LASIK.

Also, a corneal topographer usually is used; this device measures the curvature of your eye and creates a kind of "map" of your cornea. With new wavefront technology associated with custom LASIK, you also are likely to undergo a wavefront analysis that sends light waves through the eye to provide an even more precise map of aberrations affecting your vision.

Finally, the doctor will ask you about any health problems you have or medications you take. Some health conditions will disqualify you altogether for LASIK, but others may just postpone the procedure until a later date.

[For more information on disqualifiers for LASIK, please read LASIK Criteria for Success. Or, for a custom report on whether you are a good candidate for LASIK, please take our two-minute screening test.]

During LASIK Surgery

LASIK is an ambulatory procedure — you walk into the surgery center, have the procedure and walk out again. In fact, the actual surgery usually takes less than five minutes, and you're awake the whole time.

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Occasionally, the surgeon will give you a mild oral sedative beforehand.

Even though the surgery is relatively quick, LASIK is a very delicate procedure and it's important to have it performed by a highly skilled surgeon with proper equipment. You also should have someone accompany you to drive you back home afterward.

Your eyes first are anesthetized with special drops, so most people don't feel pain during LASIK surgery.

The doctor will have you lie down, then make sure your eye is positioned directly under the laser. (One eye is operated on at a time.) A kind of retainer is placed under your eyelids to keep them open — normally, this is not uncomfortable.

The surgeon will use an ink marker to mark the cornea before the flap is created. The flap is then created with either a microkeratome or with a femtosecond laser. Whichever device is used, it is securely attached to your cornea with a suction ring to prevent eye movements or loss of contact that could affect flap quality. During the procedure you won't actually see the creation of the flap, which is very thin.

An ultra-thin flap is created on the eye's surface during LASIK corrective eye surgery. After laser energy is applied to reshape the eye, the flap is replaced to serve as a type of natural bandage.

The surgeon uses a computer to adjust the excimer laser for your particular prescription. You will be asked to look at a target light for a short time while he or she watches your eye through a microscope as the laser sends pulses of light to your cornea.

The laser light pulses painlessly reshape the cornea. You'll hear a steady clicking sound while the laser is operating. You also may smell a mildly acrid odor during the corneal reshaping process.

The higher your prescription, the more time the surgery will take. The surgeon has full control of the laser and can turn it off at any time.

After the procedure is finished, you will rest for a little while. If you're having both eyes done the same day, the surgeon typically will begin working on your second eye immediately after treatment of the first eye is finished. Some people choose to have their second eye done a week later.

Your surgeon may prescribe medication for any postoperative pain, but many people feel no more than mild discomfort after LASIK. That's one advantage of LASIK over PRK, which can cause significant eye discomfort for a few days.

After LASIK: Short-Term

As with any kind of surgery, it's important that you follow your doctor's instructions to the letter. Get proper rest, use all prescribed medications as directed and call your doctor immediately if you suspect a problem. What occurs after the surgery can affect your vision just as much as the surgery itself.

Immediately after LASIK, the doctor will have you rest for a bit, then you can go home (someone else must drive). At home, you should relax for at least a few hours.

You may be able to go to work the next day, but many doctors advise a couple of days of rest instead. They also recommend no strenuous exercise for up to a week, since this can traumatize the eye and affect healing.

Avoid rubbing your eye, as there is a chance (though slim) of dislodging the corneal flap.

After LASIK: Longer Term

With LASIK surgery, most people's vision improves right away, but some find that their vision gradually improves even more over the next few days or even weeks.

LASIK outcomes may vary. Most people achieve 20/20 or better vision with LASIK. Some may achieve only 20/40 or not quite as good. In fact, 20/40 is fairly good vision. In most states, the law considers it good enough for driving.

Some patients still need glasses or contact lenses following laser vision correction, though their prescription level typically will be much lower than before.

Postoperative LASIK complications can include infection or night glare (starbursts or halos that are most noticeable when you're viewing lights at night, such as while you're driving). Rarely, people will experience improvement, then notice a gradual worsening of vision (called "regression"). If this happens, discuss it with your surgeon to determine if more surgery (called an enhancement or "touch-up") will be necessary.

Even if you see perfectly after laser eye surgery, you may still need reading glasses or bifocal contact lenses once you hit your 40s. This is because of a condition called presbyopia, which is a normal, age-related loss of near vision. Your distance vision probably will remain crisp, but seeing up close will be more difficult.

Researchers are studying ways to correct presbyopia surgically. So it's possible that you could have one of those procedures later, once they are FDA-approved.

These are important topics to discuss with your LASIK surgeon before deciding on the surgery.

[Page updated January 2010]