LASIK Eye Surgery
Medical Editorial Review by William C. Shiel Jr., MD, FACP, FACR
What is LASIK?
LASIK is a surgical procedure intended to reduce a person's dependency on
glasses or contact lenses. LASIK stands for Laser-Assisted In Situ
Keratomileusis and is a procedure that permanently changes the shape of the
cornea, the clear covering of the front of the eye, using an excimer laser.
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: persons with myopia, or nearsightedness, have more difficulty seeing distant objects as clearly as near objects.
- Hyperopia: persons with hyperopia, or farsightedness, have more difficulty seeing near objects as clearly as distant objects.
- Astigmatism: 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 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.