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What is LASIK?
The eye and vision errors
The cornea is a part of the eye that helps focus light to create an image
on the retina. It works in much the same way that the lens of a camera
focuses light to create an image on film. The bending and focusing of
light is also known as refraction. 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. Glasses or
contact lenses are designed to compensate for the eye's imperfections.
Surgical procedures aimed at improving the focusing power of the eye are
called refractive surgery. In LASIK surgery, precise and controlled
removal of corneal tissue by a special laser reshapes the cornea changing
its focusing power.
Other types of refractive surgery
Radial Keratotomy or RK and Photorefractive Keratectomy or PRK are other
refractive surgeries used to reshape the cornea. In RK, a very sharp knife
is used to cut slits in the cornea changing its shape. PRK was the first
surgical procedure developed to reshape the cornea, by sculpting, using a
laser. Later, LASIK was developed. The same type of laser is used for
LASIK and PRK. Often the exact same laser is used for the two types of
surgery. The major difference between the two surgeries is the way that
the stroma, the middle layer of the cornea, is exposed before it is
vaporized with the laser. In PRK, the top layer of the cornea, called the
epithelium, is scraped away to expose the stromal layer underneath. In
LASIK, a flap is cut in the stromal layer and the flap is folded back.
Another type of refractive surgery is thermokeratoplasty in which heat
is used to reshape the cornea. The source of the heat can be a laser, but
it is a different kind of laser than is used for LASIK and PRK. Other
refractive devices include corneal ring segments that are inserted into
the stroma and special contact lenses that temporarily reshape the cornea
(orthokeratology).
What the FDA regulates
In the United States, the Food and Drug Administration (FDA) regulates the
sale of medical devices such as the lasers used for LASIK. Before a
medical device can be legally sold in the U.S., the person or company that
wants to sell the device must seek approval from the FDA. To gain
approval, they must present evidence that the device is reasonably safe
and effective for a particular use, the "indication." Once the
FDA has approved a medical device, a doctor may decide to use that device
for other indications if the doctor feels it is in the best interest of a
patient. The use of an approved device for other than its FDA-approved
indication is called "off-label use." The FDA does not regulate
off-label use or the practice of medicine.
The FDA does not have the authority to:
- Regulate a doctor's practice. In other words, FDA does not
tell doctors what to do when running their business or what they can
or cannot tell their patients.
- Set the amount a doctor can charge for LASIK eye surgery.
- "Insist" the patient information booklet from the laser
manufacturer be provided to the potential patient.
- Make recommendations for individual doctors, clinics, or eye
centers. FDA does not maintain nor have access to any such list
of doctors performing LASIK eye surgery.
- Conduct or provide a rating system on any medical device it
regulates.
The first refractive laser systems approved by FDA were excimer lasers
for use in PRK to treat myopia and later to treat astigmatism. However,
doctors began using these lasers for LASIK (not just PRK), and to treat
other refractive errors (not just myopia). Over the last several years,
LASIK has become the main surgery doctors use to treat myopia in the
United States. More recently, some laser manufacturers have gained FDA
approval for laser systems for LASIK to treat myopia, hyperopia and
astigmatism and for PRK to treat hyperopia and astigmatism.
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