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Quality
Eye Care uses the VISX Star S4 ActiveTrak,
with active eye-tracking
and IR(Iris Registration).
The
ActiveTrak 3-D Eye Tracker is
a positioning device that uses infrared cameras
to actively follow the tiniest motions of the
eye in all three dimensions. This allows the patient
to relax during the procedure knowing that the
laser system is actively following eye movement
to ensure greater precision and accuracy during
treatment.
Variable
Spot Scanning (VSS)
is an exclusive VISX laser technology that allows
for a larger treatment area. VSS offers the doctor
greater flexibility in developing a more individualized
laser vision procedure.
Iris
Registration (IR) is the first FDA-approved,
fully automated, non-contact method of alignment
of the correct CustomVue treatment to the corneal
site. Using sophisticated algorithms and multiple
reference points on each iris, IR ensures delivery
of the treatment to the correct area of the cornea.
For
more information contact www.visx.com |
The
excimer laser is the laser used in LASIK,
LASEK,
and PRK
surgery. This particular laser is very precise, removing
as little as 0.25 microns of corneal tissue with a single
pulse. 0.25 microns is the same as one quarter of one
millionths of a meter.
 |
Human
hair etched by excimer laser |
Put
it another way, this is a fraction of the thickness
of a human hair, (pictured here) The
average treatment removes only about the thickness of
a human hair. The fact that this laser can remove so
little tissue without causing significant damage to
surrounding tissue, makes it ideal for corneal surgery
such as LASIK. The laser energy originates from a gas
mixture of argon and fluorine. The laser light itself
is ultraviolet, and thus invisible to the naked eye.
The
laser is controlled by a computer, into which the surgeon
enters the desired prescription correction for a patient's
eye. The number the surgeon programs into the computer
is the patient's refraction (the measurement of the
prescription of the eye), usually modified (by the surgeon,
based on the results of his lasik cases) to adjust for
patient age, the amount of correction, the environment
of the laser room (temperature and humidity), the surgeon's
specific technique, and other factors. The focusing
of the laser, performed by the surgeon, is extremely
important.
The
laser beam produced by the laser is very complex. The
energy or power of the beam must be very carefully monitored
by what is termed "fluence testing". The laser
should also be calibrated so that whatever the laser
is programmed to correct, will be delivered; this is
usually done by treating a plastic plate and reading
the result much like one does when measuring the prescription
of a pair of glasses. In
general, calibration should be performed before every
third eye that is treated by the laser (after treatment
of both eyes of a single patient, before the next patient).
If
you understand the above points, two things become very
clear:
(1)
Laser maintenance is critical to a good outcome.
This is not a machine that you just turn on.
The optics or focusing lenses that modify the laser
beam must be replaced at regular intervals. The humidity
and temperature should be kept as constant as possible,
otherwise the results of surgery may not be predictable.
Trained technicians are a must for laser maintenance.
(2)
The surgeon plays a major role in the surgery
and outcome. There has been a great deal of
emphasis on the high-tech equipment, but the role of
the surgeon cannot be minimized. The laser is just a
tool which depends on a skilled surgeon to be used correctly.
The actual numbers put into the laser are surgeon and
laser-dependent. Depending on who does the surgery and
which laser is used, the results can be quite different.
While
all the current lasers can theoretically treat all types
of prescriptions including astigmatism, not all the
lasers are FDA-approved to treat all of these types
of prescriptions. Treatments not FDA-approved for a
given laser can sometimes be done with that laser, in
a roundabout fashion, but such use is called "off-label".
To add to the confusion, some lasers that are FDA-approved
to treat certain types of prescriptions are only approved
to do so using the PRK technique. When these lasers
are used to treat these types of prescriptions using
the LASIK technique, such treatment is also called "off-label".
"Off-label" does not necessarily mean that
this is unsafe, only that the FDA has not examined the
data to draw any conclusions. The FDA is not in the
business of telling doctors how to practice medicine.
This is why, for example, some prescription medications
are routinely used for reasons other than the original
indications.
Currently,
treatments for farsightedness, farsightedness with astigmatism,
and mixed astigmatism are not all approved for all of
lasers in the U.S. Ask your doctor whether your prescription
can be treated with the laser he or she uses, and whether
it will need to be treated off-label. |
