LASIK is the acronym for laser in situ keratomileusis, sometimes referred to as laser-assisted in situ keratomileusis. The name refers to the use of a laser to reshape the cornea without invading the neighboring cell layers. In situ is Greek for "in the natural or normal place." Medically, in situ means confined to the site of origin without invasion of neighboring tissues. Kerato is the Greek word for cornea and mileusis means "to shape."
LASIK is a type of refractive eye surgery that may reduce a person's dependency on glasses or contact lenses by permanently changing the shape of the cornea. LASIK surgery is most commonly used to correct myopia.
LASIK is considered an elective surgery. Such surgeries are covered in many European and Asian countries. However, most United States (US), Canadian and Latin American insurance policies will not cover the procedure, nor will Medicare usually cover it. In many cases, the cost of the procedure can be covered by medical flex plans or medical cafeteria plans that allow pretax dollars to be set aside for medical expenses. Many ophthalmologists in the US also offer financing plans to patients.
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. A 2003 study reported in the medical journal Ophthalmology found that nearly 18% of treated patients and 12% of treated eyes needed retreatment. The authors concluded that higher initial corrections, astigmatism and older age are risk factors for LASIK retreatment.
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Safety Safety definitions
Pregnancy And Lactation: The U.S. Food and Drug Administration (FDA) advises that pregnant or nursing patients should avoid LASIK surgery because the measured refraction of the eye may be changed due to the pregnancy and lactation.
Effectiveness Effectiveness definitions
INSUFFICIENT RELIABLE EVIDENCE TO RATE
Hyperopia. Studies show that for low to moderate hyperopia (farsightedness), LASIK may be effective in achieving very good to excellent uncorrected visual acuity. Limited research suggests that LASIK may also be effective for hyperopic astigmatism.
Myopia. Some studies show that for mild to moderate myopia and astigmatism, LASIK may result in very good to excellent uncorrected visual acuity. However, for moderate to high myopia, studies show variable resulting uncorrected visual acuity. More evidence is needed to rate LASIK eye surgery for these uses.
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Dosing & administration
General: Immediately after the procedure, the eyes may burn, itch, or feel like there is something in it. Patients may experience sensitivity to light, glare, starbursts or halos around lights, or the whites of the eye may look red or bloodshot. It is estimated that 3-6% of patients who undergo this procedure will have a side effect or complication. According to several large studies, there is approximately a 2% intra-operative (and 3-5% post-operative) complication rate. Most complications do not result in loss of two or more lines of best-corrected visual acuity or interfere with vision long term. The rate of severe complications is approximately less than 1%. Some reported complications of LASIK surgery include: overcorrection and under-correction, visual acuity fluctuation, light sensitivity, double vision, debris or growth under flap, induced astigmatism and macular hole.
Ocular/Otic: Side effects such as dry eyes, nighttime starbursts, and reduced contrast sensitivity may occur relatively frequently. Other side effects may include: corneal infection, corneal scarring, permanent warping of the cornea and an inability to wear contact lenses, loss of vision, permanent vision loss, flap complications, scratchiness, patches of red or pink in the white of the eye and decreased distance vision at high altitudes.
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Mechanism of action
LASIK surgery is a type of refractive eye surgery. Refractive eye surgery is a procedure that changes the way the eye refracts light. As light rays enter the eye, the cornea and lens bend (refract) the rays to focus them on the back of the eye, the retina. If a patient has a refractive error, the eye is shaped in such a way that light rays are not sharply focused on the retina.
The cornea is the part of the eye that helps focus light to create an image on the retina. Usually the shape of the cornea and the eye are not perfect and the image on the retina is out-of-focus (blurred) or distorted. These imperfections in the focusing power of the eye are called refractive errors.
There are three primary types of refractive errors: myopia, hyperopia and astigmatism. Persons with myopia, or nearsightedness, have more difficulty seeing distant objects as clearly as near objects. Persons with hyperopia, or farsightedness, have more difficulty seeing near objects as clearly as distant objects. Astigmatism is a distortion of the image on the retina caused by irregularities in the cornea or lens of the eye. Combinations of myopia and astigmatism or hyperopia and astigmatism are common.
In LASIK, the laser is used to smooth the irregularly shaped cornea into a more normal shape which then corrects the myopia, hyperopia and/or astigmatism.