More than one million LASIK surgeries are performed in the United States each year. But despite LASIK’s widespread use, for those 12 million Americans with farsightedness, it’s no longer the only -- or always the best -- option.
LASIK, which stands for laser-assisted in-situ keratomileousis, is a surgical procedure that uses a laser to reshape the cornea. When people have hyperopia, better known as farsightedness, they also tend to have flatter corneas than people who do not require corrective lenses for optimal sight. For this reason, light rays focus behind, instead of on, the retina, blurring close vision. LASIK corrects the focus by increasing the cornea’s curve.
What is LASIK? First, using a surgical blade, surgeons create a flap of corneal tissue thinner than a strand of hair, then use a laser to reshape the cornea. Afterwards, they fold back the flap, as a kind of natural bandage that reseals itself to the eye. Recovery from LASIK takes a week, usually speeded by prescription eyedrops or ointment. But it may take six months for vision to stabilize from LASIK.
Miraculous as the procedure sounds, LASIK also has limitations. Most patients over age 45 still need reading glasses to correct presbyopia, farsightedness that results from an age-related inability to alter the shape of the eye’s natural lens. And LASIK is not appropriate for someone with thin corneas (which an ophthalmologist can detect). Results are poorer for those with more severe farsightedness, and there is risk that the cornea’s remodeled shape will regress to the pre-LASIK shape sometime after the procedure.
Possible LASIK complications include increased sensitivity to light, halos around lights at night, and dry eye. Infection and increased eye pressure leading to glaucoma are also possible.
Other Laser Choices
- IntraLase. The most recent advance in LASIK uses a computer-guided laser rather than a scalpel to create the corneal flap. The IntraLase directs pulses of light around the cornea’s edges, each forming a tiny bubble. The bubbles ultimately connect to create a corneal flap. The surgery then continues like traditional LASIK.
This procedure is preferable for those with thin or flat corneas and may have fewer complications and greater accuracy than traditional LASIK, but this claim has not been well substantiated.
- Wavefront-guided LASIK. The Wavefront method uses an instrument called an aberrometer to send light waves into the eye, measuring their distortion as they bounce back. Using these measurements, surgeons program a laser to customize the reshaping of the cornea. Wavefront has less risk of causing poor night vision than traditional LASIK. And 92% of those treated with Wavefront end up with 20/20 vision (without glasses) compared with 86% with traditional LASIK. But as with traditional LASIK, postoperative risks include dry eye. And patients must have even thicker corneas than for traditional LASIK: Wavefront may remove 10% more tissue.
- PRK (photorefractive keratectomy). In a PRK, the surgeon first removes the epithelium, or layer of cells covering the cornea, then reshapes the cornea using the same laser as used in LASIK to remove tissue from the cornea. Although LASIK offers shorter healing time and less discomfort, PRK suits someone with thin corneas or other corneal abnormalities and is generally a safer procedure.
- LASEK (Laser-assisted epithelial keratomileusis). LASEK resembles LASIK, except that surgeons apply alcohol to the epithelium for 30 seconds, loosening surface cells from the cornea before peeling the epithelium back and using a laser to reshape the cornea. The epithelium is replaced, and a contact lens is placed over it to speed healing. Like PRK, this option may be preferable to LASIK for people who have thin corneas or corneal disease.
- Laser thermal keratoplasty. The heat from a special thermal laser is applied to the outside edge of the cornea. The heat tightens the edges, causing the center of the cornea to rise. Ideal for mild farsightedness or presbyopia, it’s a short, painless procedure. It also carries less risk of infection or complications than traditional LASIK. However, in some patients, the effect of the procedure wanes with time, and its predictability is imperfect.
- Non-laser Choices -- Conductive keratoplasty. Using a handheld probe, the surgeon applies radio-frequency energy to the edges of the cornea. Like a thermal laser, the energy shrinks the edges, raising the center of the cornea. This treatment is used for hyperopia and presbyopia. Unlike some procedures, it improves vision immediately with little discomfort. However, its correction may not last, making a repeat procedure necessary.
- Refractive lens exchange (RLE). RLE is essentially the same as cataract surgery, but its purpose is to correct far- or nearsightedness. The lens of the eye is replaced with a silicone or acrylic intraocular lens (IOL). This is preferable to LASIK for those who have thin corneas, dry eye, or other cornea problems and for those who are severely farsighted. It’s a particularly good option for those who are developing cataracts.
- Multifocal intraocular lenses (multifocal IOLs). These lenses permit simultaneous focus for both near and far vision. As in traditional cataract surgery, the lens is implanted to replace the eye’s lens. Multifocal IOLs are more likely to offer freedom from glasses or contacts, but there’s no guarantee. And they carry a greater possibility of sensitivity to glare and halos at night (but this side effect occurs less often with second generation lenses).
- Phakic intraocular lenses (phakic IOLs). This procedure can be used in people whose farsightedness is more severe than LASIK can correct. An implantable contact lens is placed in front of the lens through a small incision in the cornea. Because of the incision, phakic IOLs carry more risk than LASIK or PRK. They may also be associated with the development of cataracts and other intraocular complications.
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Posted in Vision on November 23, 2007
Reviewed July 2009
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