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

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.

LASIK is done most often on people who use glasses or contact lenses because of nearsightedness (myopia). It is occasionally used to correct farsightedness. It may also correct astigmatism.

FDA and American Academy of Ophthalmology developed guidelines and recommendations that detail who would be a good candidate for LASIK.

• You should be at least 18 years old (21 in some cases, depending on the laser used), since the vision of people younger than 18 usually continues to change. An exception is the small child with one very nearsighted and one normal eye. The use of LASIK to correct the very nearsighted eye may prevent amblyopia (lazy eye).
• You should not have this procedure if you are pregnant or breastfeeding since these conditions can affect eye measurements.
• You should not have this procedure if you take certain prescription drugs, such as Accutane or oral prednisone.
• Your eyes must be healthy and your prescription stable. If you're are nearsighted, you should postpone LASIK until your condition has stabilized. Nearsightedness may continue to increase in some patients until their mid to late 20s.
• You should be in good general health. LASIK may not be recommended for patients with diabetes, rheumatoid arthritis, lupus, glaucoma, herpes infections of the eye, or cataracts. You should discuss this with your surgeon.

Other recommendations:

• Weigh the risks and rewards. If you're happy wearing contacts or glasses, you may want to forego the surgery.
• Understand your expectations from the surgery. Are they realistic?

For patients with presbyopia, it's important to note that LASIK cannot correct vision so that one eye can see at BOTH distance and near. However, LASIK can be done to allow one eye to see near and the other far. If you can adjust to this correction, it may eliminate or reduce your need for reading glasses. In some instances, surgery on only one eye is required. If your doctor thinks you're a candidate, ask about the pros and cons.

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.

Immediately following the surgery, there may be a sense of burning, itching, or a feeling that something is in the eye. There may be mild discomfort for which the doctor may prescribe a mild pain reliever medication. It is very important NOT to rub the eye after LASIK, so that the flap does not dislodge or move.

The day of surgery, vision generally is blurry or hazy but by the next day the blurriness improves. The doctor should be called immediately if there is severe pain or any of the symptoms worsen BEFORE your scheduled follow-up appointment (24-48 hours after surgery).

At the first doctor visit after the surgery, the eye shield will be removed and the doctor will examine your eye and test your vision. You may receive eye drops to help prevent infection. Do not drive until your vision has improved enough to safely do so.

Other things to avoid include swimming, hot tubs, whirlpools, contact sports, lotions, cremes, and eye make-up for between 2-4 weeks after surgery. The doctor will give you specific instructions.

It may take up to 3-6 months for your vision to stabilize after surgery.

Some people need an additional surgery to get the best possible results. However, a second surgery may improve distant vision, it may not relieve other visual symptoms such as glare, haloes, or difficulty with night driving. These are commonly reported complaints after LASIK surgery. Often, these problems will go away after 6 months, but a small number of people continue to have problems with glare.

If your distance vision has been corrected with LASIK, it is likely that you may still need reading glasses around age 45.

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