Refractive Surgery
Refractive surgery is an innovative approach to correcting
the common errors of refraction. Refractive surgery includes
a variety of techniques which surgically alter the eyes' flawed
focus, actually treating the cause for the refractive error
and lessening or eliminating dependence on corrective lenses.
Modern refractive surgery is very safe, accurate and predictable.
Almost all patients will achieve the stated goal of significantly
reducing or eliminating dependency on eyeglass or contact
lens correction for distance vision. Reading glasses, however,
may still be needed in patients over the age 40.
The most highly regarded refractive surgical option is Lasik
or laser assisted in-situ keratomileusis. Altering the surface
contour of the cornea to flatten or steepen the curvature
of its central zone is the basis of all refractive surgical
procedures. As a replacement to radial keratotomy that involves
incisions which modify the curvature of the cornea, Lasik
utilizes a computer-controlled, short wavelength high-energy
light source that precisely sculpts and polishes a new surface
on the cornea. Painless, the procedure takes only a few minutes.
Clinical trials on individuals with otherwise normal nearsighted
eyes began in Europe in 1988 and in 1990, were joined by several
university centers in the USA. The excimer laser procedure,
known as photorefractive keratectomy ("PRK"), and
its cousin LASIK, are very effective indeed. The cumulative
data based on millions of patients continues to confirm its
impressive record of safety and predictability. Since its
release for general use by the FDA in 1996, PRK and LASIK
utilizing the excimer laser has become the most affective
and accurate procedure to surgically correct nearsightedness,
farsightedness and astigmatism. There is a third procedure
referred to as Epi-K. Lasik, PRK, and Epi-K are essentially
identical procedures except for the way we handle the surface
of the cornea. In LASIK, a flap of cornea is reflected back
exposing the corneal bed. Treatment with the excimer laser,
as in standard PRK, beneath the retracted cap alters the curvature
in the desired amount. The cap is then repositioned as it
was originally without suturing or bandages. Comfort is excellent
and vision usually recovers very quickly often adequate to
drive a car by the next day. LASIK is done in a specially
equipped "clean room". Eye drop anesthesia and,
in some cases, mild sedation assures a painless outpatient
procedure. Healing and visual recovery is rapid without need
for prolonged eye drop medications. With LASIK, freedom from
dependence on eyeglass or contact lens correction is a goal
that is almost always realized.
PRK, which predates Lasik, is an identical procedure except
that we do not make a flap of cornea but instead, treat the
surface of the eye by reconturing it. The surface now needs
to heal and we use medications, drops, and bandage soft contact
lenses to promote healing and provide comfort. The soft bandage
contact usually is in the eye for about one week and drops
need to be continued for up to 4 months to allow safe healing
with excellent vision. In contrast, with Lasik, the drops
are normally used for 4 days! In Epi-K, we remove the surface
epithelial cell layer in one continuous piece which may be
replaced after the treatment with the laser. How we remove
the epithelium or make the flap varies slightly depending
upon the procedure.
In Lasik, we create a thin corneal flap by using a surgical
keratome. This is a painless, very reliable, and safe procedure
that is done just before laser sculpting of the surface. The
entire procedure takes only a few minutes and again requires
only topical anesthesia. There is another way to create the
corneal flap in Lasik that utilizes a different laser, the
Femtosecond laser by Intralase. This infared, long wave length
laser creates the flap. This is followed by the excimer laser
which sculps the bed under the flap. Both the surgical keratome
and the Intralase are very effective.
Alcon vs Visx Systems
The Alcon laser system utilizes a Flying Spot treatment which
applies thousands of spots of laser directed by the softwear
of the laser. With Visx, the laser system is a Broad Beam
laser that applies a large beam starting in the center and
expanding to cover the entire surface.
Custom Laser Treatments
One of the more recent advances is the development of Wavefront
Custom laser treatment. Dr. Richard Tax has chosen two different
systems: The Alcon Wavescan and the Visx Customvue. In Custom
treatment, the patient is measured first on a wavescan analysis
topographer that takes a “picture” of the surface.
It measures low order and higher order optical aberrations,
and tells the laser how to treat them to reduce or in some
cases eliminate them. Lower order aberrations are the same
as farsightedness, nearsightedness, and astigmatism. The higher
order optical aberrations, which previously could only be
measured in a laboratory, are now measureable. Coma, trefoil,
quadrafoil, and spherical aberrations are the major aberrations
that can be treated. The advantages are potentially better
dim and night vision, less glare and haloes, more accuracy
and reduced incidence of touch up procedures referred to as
enhancements.
previous
| next
|
