For many people, laser eye surgery can correct their vision so they no longer need glasses or contact lenses. Laser eye surgery reshapes the cornea, the clear front part of the eye. This changes its focusing power.

There are different types of laser eye surgery. LASIK - laser-assisted in situ keratomileusis – is one of the most common. Many patients who have LASIK end up with 20/20 vision. But, like all medical procedures, it has both risks and benefits. Only your eye doctor can tell if you are a good candidate for laser eye surgery.

LASIK eye surgery changes the shape of your cornea — the transparent membrane that arcs over your pupil and the colored part of your eye (iris). After the procedure, your cornea should bend (refract) light rays to focus more precisely on your retina rather than at some point beyond or short of your retina.

LASIK eye surgery may be an option for you if you have nearsightedness (myopia), farsightedness (hyperopia) or astigmatism. Nearsightedness occurs when the eyeball is slightly longer than normal or when the cornea curves too sharply, causing light rays to focus in front of the retina and blurring distant vision. Farsightedness is the opposite, in a way: A shorter-than-average eyeball or too-flat cornea focuses light behind the retina instead of on it, making near vision and sometimes distant vision blurry. When the cornea curves or flattens unevenly, the result is astigmatism, which disrupts focus of near and distant vision.

Your eye doctor will likely recommend that you try other ways of correcting your vision before you turn to LASIK eye surgery or another similar procedure. Glasses or contact lenses are your first option. Unlike sight-threatening eye diseases, refractive errors aren't progressive in themselves, and they may actually improve in middle age. Some doctors are reluctant to endorse LASIK eye surgery, reasoning your eyes are basically healthy even if you have nearsightedness or farsightedness. A good surgical outcome depends on careful evaluation of your eye before the surgery.

What might disqualify you from having LASIK eye surgery?

LASIK eye surgery poses particular risks for some people. You should definitely not have this surgery if you have:

Can someone with presbyopia get LASIK eye surgery?

Certain people with presbyopia may benefit from LASIK eye surgery, although there are limitations. Most people in their 40s have some signs of presbyopia — a refractive error that develops as you age — such as difficulty reading or performing other close-up tasks. The condition is usually well managed with the use of reading glasses.

If you have presbyopia, LASIK eye surgery may give you clear distance vision, but it might make it even more difficult for you to see objects close up. To avoid this, you might choose to have your vision corrected for monovision. With monovision, one eye is corrected for distant vision and the other for near vision. Not everyone is able to adjust to or tolerate monovision, so it's wise to undergo a trial with contact lenses before opting for a permanent surgical procedure.

How do you prepare for LASIK eye surgery?

Before surgery, your eye doctor takes a detailed medical history and uses specialized equipment to carefully measure your cornea, noting the shape and any irregularities.

If you wear contact lenses, you'll need to switch to glasses full time a few weeks before this exam. Contact lenses can distort the shape of your cornea, which could lead to inaccurate measurements and a poor surgical outcome.

Skip your eye makeup and eye cream on the day before and the day of your surgery. Your doctor may also instruct you to clean your eyelashes daily or more often in the days leading up to surgery, to remove debris and minimize your risk of infection.

You'll need to have someone drive you to and from your surgery. Immediately after surgery, you might still feel the affects of medicine given to you before surgery and your vision may be blurry.

Refractive surgery is usually considered elective surgery — which means it isn't vital to your health and well-being. For this reason, Medicare and most insurance companies won't cover the cost of the surgery. So be prepared to pay out-of-pocket for your expenses.

How is LASIK eye surgery done?

LASIK is performed using a laser programmed to remove a defined amount of tissue from your cornea. With each pulse of the laser beam, a tiny amount of corneal tissue is removed. The laser allows your eye surgeon to flatten the curve of your cornea or make it steeper. Often, LASIK is performed on both eyes on the same day.

During surgery
You will receive anesthetic eyedrops that numb your eye during the LASIK procedure, which helps ensure you'll experience little pain. You may also be given medicine to help you relax. Your eye surgeon uses a special blade or cutting laser to cut a hinged flap about the size of a contact lens away from the front of your eye. Folding back the flap allows your doctor to access that part of your cornea that needs reshaping. Using a laser, your eye surgeon then adjusts specific parts of your cornea. After reshaping is complete, the flap is folded back into place and usually heals without stitches.

During your presurgical eye exam, your eye doctor uses highly specialized instruments to determine which specific areas of your cornea need to be flattened or curved. This allows your eye doctor to chart your eye and remove tissue from your cornea very precisely. Wavefront-guided LASIK, a new type of LASIK procedure, uses a special device called a wavefront scanner that allows your doctor to create a highly detailed chart — like a topographical map — of your eye. Theoretically, the more detailed the measurements, the more accurate your eye doctor can be in removing corneal tissue. Wavefront-guided LASIK technology continues to evolve.

After surgery
Immediately after surgery, your eye may burn or itch and be watery. You'll probably have blurred vision. You may be given pain medication or eyedrops to keep you comfortable for several hours after the procedure. Your eye doctor might also ask you to wear a shield over your eye at night until your eye heals.

Typically you're able to see the day of your surgery, but your vision won't necessarily be better right away. Expect your vision to improve over the next two to three months. Most people who have refractive surgery eventually attain 20/25 or better vision. Your chances for improved vision are based, in part, on how good your vision was before surgery.

Other types of refractive surgery

Your eye doctor may recommend another type of refractive surgery if you're not a good candidate for LASIK eye surgery. These include:

Photorefractive keratectomy (PRK). PRK is sometimes used if you have a low to moderate degree of nearsightedness or farsightedness, or if you have nearsightedness with astigmatism. PRK removes the thin surface layer of your cornea (epithelium). Your eye surgeon then uses a laser to flatten your cornea or make its curve steeper.

The exposed surface of your cornea repairs itself, assisted by a contact lens you wear as a bandage over your eye for three or four days after surgery. You might have eye pain for a few days until your cornea heals. It generally takes up to a week for your eye to regenerate the surface tissue that was removed. During this time you'll notice variations in your vision. It may take three to six months before your vision improves completely. Most people undergoing PRK have both eyes done on the same day.

PRK has become less common in recent years because more eye surgeons prefer the LASIK procedure. Healing after LASIK is more predictable and usually involves less discomfort and scarring.

Laser epithelial keratomileusis (LASEK). LASEK is similar to LASIK eye surgery and might be an option if you aren't eligible for LASIK. During a LASEK procedure, a much thinner layer — the surface layer (epithelium) — of your cornea is folded back to allow the laser to focus on parts of your cornea that need reshaping. The epithelial flap is then replaced.

If you have very thin corneas, you might be a better candidate for LASEK because the procedure allows your doctor to remove less of your cornea. People who play sports or have jobs that carry a high risk of eye injuries might also prefer LASEK because a thinner flap means less damage to your vision should the flap be torn before it can heal. As with LASIK, the LASEK procedure can be done on both eyes on the same day.