LASIK stands for
Laser Assisted
In-situ
Keratomileusis. This is a long name that means reshaping the corneal
curvature by using laser energy. By reshaping the corneal curvature, it
is possible to refocus the eye, reducing or eliminating the need for
eyeglasses.
Call us at 512-377-5777
directly for your appointment.
How The Eye Works
In order to understand how this works, it
is important to review how the eye works, and how physicians have
approached correcting vision.
The eye is often described as being
similar to a camera, having a lens system at the front, and a method for
creating or storing an image at the back. In a camera, the lens system
focuses light, and then the light strikes the emulsion of the film,
creating an image. That image is then sent to a photoprocessor and the
result is a picture.
In the eye, the cornea, or clear front
surface of the eye, along with the lens of the eye, which sits just
behind the colored part of the eye (iris) and pupil (the black hole in
the center of the iris) form the lens focusing system. The retina, which
is the neurosensory part of the eye, lines the back of the eye and is
similar to the camera film. The optic nerve, which connects the eye to
the brain, transmits the signals created on the retina to the brain for
“processing”.
If the cornea and lens focus images
properly on the retina, clear vision is created. If the images are
focused in front of, or behind the retina, blurry vision results.
Nearsightedness (myopia) occurs when images focus in front of the
retina; Farsightedness (hyperopia) when the images focus behind the
retina. Both nearsightedness and farsightedness usually occur because
the eye is too long (nearsighted) or too short (farsighted).
It is not possible to change the length
of the eye, just as it is not possible to make someone taller or their
feet smaller. It is , however, possible to refocus the eye.
Refocusing The Eye
Refocusing the eye is possibly by
changing the focal power of either the lens of the eye or the cornea of
the eye. The lens, behind the pupil, can be removed and replaced by an
artificial lens of a different focal power. Dr. Thorne does this every
week when he removes cataracts. A cataract is just a natural lens that
has become cloudy and yellow-brown with age. Replacing the lens is not
usually done on young, healthy patients. A better option for refocusing
the eye is by changing the cornea.
The cornea, or windshield of the eye, is
the clear part of the eye at the very front. Because of its location, it
is easy for a surgeon to work on. Additionally, the cornea is the main
refracting surface of the eye (responsible for about 70% of the focusing
power). By changing the corneal power a small amount, a large amount of
refocusing can occur.
The cornea, if examined closely,
demonstrates a certain amount of curve. The more curved it is, the
steeper the cornea, the more strongly it focuses light. The less curved
it is, the flatter the cornea, the less it focuses light. This fact is
the basis of corrective eye surgery.
In nearsightedness, the light rays are
focusing in front of the retina. If the corneal curve can be made a
little flatter, it will focus less strongly, moving the nearsighted
image back in the eye to a position closer to the retina. The reverse is
accomplished in farsighted eyes by steepening the cornea and thus
bringing images up from behind the retina to the correct focal point.
The first attempts to correct
nearsightedness were performed in Japan and consisted of creating
relaxing incisions in the cornea, allowing the center to move back as
the outside zones of the cornea relaxed. A Russian ophthalmologist, Dr.
Fyodorof popularized this procedure in the 1980’s, proving
unequivocally that it worked. This procedure was called Radial
Keratotomy, or cutting the cornea in a spoke-like pattern. RK, as it is
usually called, is still a good procedure for certain patients, and Dr.
Thorne is an expert in performing it.
RK’s popularity was limited by the
amount of nearsightedness it could correct (only up to about 5 diopters),
and the often mentioned halos and small fluctuations is vision
throughout the day.
Laser
In 1979, IBM patented a new laser, called
an EXCIMER (for excited dimer),
designed for etching computer chips. As
chip technology changed, it became obsolete. Investigations did continue
using the laser for medical purposes. It was discovered that the excimer
was especially accurate in treating the cornea. The laser, not using
heat, could remove microscopic bits of corneal tissue very accurately
and precisely where the laser was focused, leaving the surrounding
tissue undisturbed.
The Excimer was initially used to perform
PhotoRefractive
Keratectomy(PRK). PRK simply means removing tissue with
light rays from surface of the eye. The procedure worked by removing a
tiny amount of tissue from the front of the cornea just over the pupil,
creating a slightly flat spot. That flat spot refocused light entering
the pupil further back, closer to the retina. It was soon discovered
that the very outer covering layer of the cornea, the epithelium, did
not absorb laser energy well, so the surgeons started wiping it away,
treating the underlying cornea, and then allowing the epithelium to grow
back. Normally, this took about 3 days. The vision was blurry and the
eye scratchy during that period, but subsequently the visual results
were excellent.
Like PRK has limitations, but is
still an excellent procedure. In PRK, the more nearsighted the eye, the
more tissue needs removing. The more tissue removed, the more likely
scar tissue will form, which in the eye is cloudy, and therefore if too
much laser is performed, it is possible to get a slight haze in the
visual axis. This fact stimulated the development of LASIK.
Like PRK, LASIK improves vision by
flattening the central cornea by removing a microscopic amount of
tissue. The difference is that in LASIK, the tissue is removed from the
deeper layers of the cornea. This is done by creating an anterior
corneal flap that is about 30% of the thickness of the cornea. This is
performed by using an instrument called a MICROKERATOME (microscopic
corneal cutter). This instrument delicately creates a round flap that is
not completely removed, but merely folded out of the way. The laser then
removes the tissue, and the flap is returned to its original position.
The flap sticks down without sutures, like two pieces of plate glass
stick together. The flap is really hinged, resembling the cover of a
book.
With LASIK, it is possible to correct
high degrees of nearsightedness safely and effectively.
LASIK can also be used to correct
farsightedness. The procedure is exactly the same, but the central
cornea needs to be steepened, not flattened as in nearsightedness, so
the laser is applied to the zone surrounding the center, tightening it
up and making the center zone “shoulder up” to increase its curve.
What about astigmatism?
Astigmatism means
that the curve of the cornea is steeper in one meridian than in the
other. An eye without astigmatism is like a basketball…because it is
round, it has the same radius of curvature in all directions. Because
the radius of curvature determines how strongly light is focused, in
spherical corneas, light entering the eye from any direction is focused
at the same spot. An eye with astigmatism is like a football…steeper
around the middle, and flatter from end to end, creating two radii of
curvature, and hence two focal points. With LASIK, the laser can be
programmed to correct both radii of curvature, successfully correcting
vision is patients with astigmatism.
What about needing reading glasses ?
The
need for reading glasses which magnify the print occurs to almost
everyone who is over 45. It occurs because the natural lens of the eye
loses its elasticity as it ages, so it can no longer automatically focus
from distance to near. LASIK will not correct that problem, and most
patients over 45 who have LASIK will need reading glasses.
Monovision is correcting one eye fully
for distance and leaving the other a little under corrected for distance
so that it can see better up close. Many people who are middle age like this
option.
What about financing?
George C. Thorne, M.D. offers our patients the opportunity
to finance
your laser vision correction procedure at 0%
interest with CareCredit, a
healthcare 
financing plan that assists our patients in paying for their
treatment over time, without any up-front payment required. It's ideal
for co-payments, deductibles, and treatment not covered by insurance.
With CareCredit, you can take care of the bill without another thought
and focus on what's most important - your eyes.]
Using CareCredit for your
healthcare expenses leaves your major credit cards available for other
important purchases and unexpected expenses. CareCredit has
interest free plans available with flexible payment terms. And if you're
looking for a way to stretch your payments out over a longer time
period, they have low interest plans that give you a longer time to pay.
To obtain a CareCredit
Instant Credit Application, click here.
