LASIK eye surgery

Alternative names
Laser-Assisted In Situ Keratomileusis; Laser vision correction

LASIK is a surgical procedure that can reduce a person’s dependency on glasses or contact lenses by permanently changing the shape of the cornea (the delicate clear covering on the front of the eye). 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.
LASIK eye surgery is performed most often on people who have myopia (nearsightedness), which means that they only clearly see nearby objects; anything far away is blurry.


A complete eye examination will be done before surgery to make sure your eyes are healthy. Once this is determined, the doctor will measure the curve of the cornea and the size and position of the pupils, the shape of the eyes (making sure there are no irregularities that would prevent LASIK as an option), and the thickness of the cornea (making sure there will be enough tissue left, once the cornea is cut and reshaped).

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 the 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 myopia (nearsightedness). It is occasionally used to correct farsightedness. It may also correct astigmatism.

The FDA has approved the Excimer Laser to correct nearsightedness up to -12.00D with -4.00D of astigmatism, and farsightedness from +1.00 to +6.00 with 1.00D of astigmatism. (Diopter, symbol D, is the measurement of the refractive error. A negative D value indicates nearsightedness and a positive D value indicates farsightedness.)

The FDA, in cooperation with the American Academy of Ophthalmology, has developed the following guidelines and recommendations for good candidates for LASIK:

  • You should be at least 18 years old (21 for some lasers), 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 be pregnant or nursing because these conditions might change the measured refraction of the eye.  
  • You should not be taking certain prescription drugs, such as Accutane or oral prednisone.  
  • Your eyes must be healthy and your prescription stable. If you’re myopic, you should postpone LASIK until your refraction has stabilized, because myopia 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.  
  • 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, LASIK cannot correct so that one eye can see at BOTH distance and near. However, LASIK can be used to correct one eye for distance and the other for near. 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.


  • Over- or under-treatment of the condition may occur, requiring additional surgery, contact lens, or glasses.  
  • Reading glasses may still be needed after surgery.  
  • Some patients, although they may see much better than before LASIK without glasses, will still need glasses for their best vision.  
  • Problems with night driving or visual symptoms, such as glare and haloes.  
  • Problems with a decrease in contrast sensitivity, and even with 20/20 vision, objects may appear fuzzy or gray.  
  • Corneal infection.  
  • Corneal scarring, permanent warping of the cornea and an inability to wear contact lenses.  
  • A loss of vision - not seeing as well after surgery, even with glasses or contacts as before the surgery.  
  • Permanent vision loss.  
  • Flap complications.  
  • Light sensitivity.  
  • Dryness.  
  • Scratchiness.  
  • Patches of red or pink in the white of the eye.  
  • Decreased distance vision at high altitudes.

Expectations after surgery

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 vision to stabilize after surgery.  
  • The most common complaints after LASIK are glare, haloes, and difficulty with night driving. Often, these problems will go away after 6 months, but a small percentage of people continue to complain about glare.  
  • Sometimes additional surgery may be needed in order to get the best possible vision. These re-operations may be called “enhancement surgery.” Generally, while the distance vision may improve with enhancement surgery, other visual symptoms such as glare or haloes may not.  
  • The Academy of Ophthalmology (AAO) reports that of approximately 500,000 Americans who had LASIK surgery in 1999, 70% had 20/20 vision after surgery.  
  • If your distance vision has been corrected with LASIK, it is likely that you may still need reading glasses around age 45.  
  • The long-term effects of LASIK past 5 years after the surgery are yet to be determined.

Johns Hopkins patient information

Last revised: December 7, 2012
by Mamikon Bozoyan, M.D.

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