Lasik
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.
See the section on FDA-approved lasers for more details
on which lasers have received FDA approval and the specific
indications and treatment ranges for which they were approved.
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