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_Lasik Surgery _
By: Rambod Mostafavi
Seeing well without contact lenses and glasses is the dream of millions of
Americans and modern medical science has enabled that dream to come true
(Caster, 8). Since first grade, Dede Head, a 30-year-old fitness trainer in
North Carolina, has worn glasses to correct sever nearsightedness and
astigmatism. Over the years she became accustomed to wearing glasses and
contacts, but this has limited many important aspects of her life, including
sports. She then heard of a laser eye surgery that “supposedly”, helped to
correct a person’s vision by means of lasers. She immediately signed up for
the procedure and ever since that day, she has not worn glasses or contacts.
Dede is just one of the eight hundred-fifty-thousand people who have undergone
a procedure by the name of LASIK or Laser In-Situ Keratomileusis. If surgical
procedures were movies, LASIK would be this years box office smash as it has
received much media coverage and many praises; however, not that many people
know what LASIK is, what the advantages and disadvantages are, and most
importantly if LASIK is right for them (Buratto, 1). LASIK is basically a type
of laser surgery which can help correct nearsightedness (myopia), which is the
inability to see distant objects, farsightnedness (hyperopia), which is the
inability to see close, and astigmatism, the inability to focus light waves
evenly. LASIK has grown greatly in the last year, mostly because of 4 reasons;
it is fast (procedure takes about 5-10 minutes), safe, painless, and the
results are almost always prolificThe eye is just like a camera because it
works by focusing light waves that pass through it. Light rays that enter the
eye must first pass through the most outer layer of the eye called the cornea.
The cornea performs 2/3 of the focusing process, the remainder of is then
completed by the crystalline lens which further focuses the light on the
retina. This requires extreme precision in that the focused light must fall
exactly at the level of the retina (Gallo, 126). The retina is a nerve tissue
that carpets the inner surface of the eye, much like wallpaper covers all
aspects of a wall. The retina converts the light into electrical signals,
which are transmitted to the brain by the optic nerve. Just as a camera cannot
produce clear photographs of the image if the incoming light is not focused on
the film, we cannot produce a clear vision if the cornea and crystalline lens
do not focus the light precisely on the retina. This is where LASIK steps in.
A laser is a device that creates a very special kind of light energy that is
usually invisible to the human eye (Caster, 16). In LASIK, ophthalmologists
use a certain type of laser called the excimer. By using invisible ultraviolet
light, the excimer is able to break covalent bonds between molecules. What
sets excimer aside from other lasers used in medicine is the wavelength used.
At one-hundred ninety-three nm (nanometers), excimer lasers remove tissue by
breaking the covalent without creating much thermal energy (Slade, 25). This
allows for precise removal of tissue with minimal surrounding tissue damage.
The very thin layer of the cornea that is removed, changes the curvature of
the cornea ever so slightly, thus then results in a change in the light
focusing ability. In nearsightedness (myopia), light rays from distant objects
are not focused on the retina, but instead they are focused in front of the
retina (See Figure 1). Therefore to correct nearsightedness in a LASIK
procedure, the curvature of the cornea must be decreased or in another words
made flatter by removing corneal tissue in a disc-shaped pattern, or from the
central cornea. A computer determines the exact pattern and number of pulses
that are needed to do this. In farsightedness (hyperopia), light rays from
distant objects are focused not onto the retina, but behind it (See Figure 1).
To correct this, the central portion of the cornea must be made steeper; and
this is accomplished by removing corneal tissue in a donut shaped pattern, or
in another words more from the peripheral areas. Eyes with astigmatisms focus
light waves unevenly because of the irregular shape of the cornea; football
shaped as opposed to the usual round, basketball shaped corneas. The excimer
laser can remove corneal tissue asymmetrically, and so the end result is a
round, symmetrical surface (Sloat, 90). LASIK, did not just develop suddenly
overnight in some ophthalmologist’s mind; however, LASIK is part of an evolved
procedure (Gallo, 127). Today’s vision correction revolution dates back
decades through the sheer genius, persistence, and ingenuity of Professor Jose
Barraquer (Slade, 8). Refractive surgery, which is the type of surgery LASIK
is characterized as, started in Bogota, Columbia in 1948 when Barraquer
started performing a procedure called Freeze Keratomileusis. This procedure
involved adding a disc of corneal tissue (donated from another person) with a
predetermined curvature in the cornea giving it structure. In a journal found
2 decades after this procedure, it stated that patients who had myopia could
see better after the procedure; however he stated a few months after the
surgery, that some patients would lose their eyesight due to infection. The
reason for this was that Barraquer used an unsterilized shaver to cut the
cornea. It was not until the late 1970’s that refractive surgery resurfaced
when US surgeons visited the Soviet Union. The surgeons brought back a
procedure called Radial Keratotomy (RK) which made spokelike incisions in the
cornea by using a handheld diamond scalpel. The results were good, but
scientists noticed that the incisions structurally weakened the eye.
Scientists and doctors worked for 2 decades to develop Radial Keratotomy into
a procedure that was both safe and produced good results. Then in 1994, a
company by the name of Summit Technologies developed the first excimer laser
that could be used for surgery. A year after, the Food and Drug Administration
(FDA) approved this excimer laser and stated that it could only be used to
correct mild nearsightedness in a procedure called Photorefractive Keratectomy
(PK). In PRK, surgeons scrape away the very outer layer of the cornea (less
than 5% thickness of the entire cornea) and then use the excimer laser to
vaporize the underlying corneal tissue to a predetermined depth (no more than
fifty percent thickness of the cornea). These results were very good as 90
percent of the cases showed that the patients achieved at least 20/40 vision,
which is the usual standard to pass a driver’s license test; however, the
surgery had many drawbacks. While the procedure itself was not painful,
patients had significant pain and discomfort for almost a week after the
surgery (Gallo, 129). Worst of all, it often took a week to even see anything
and six months to get the full benefits of the surgery (Gallo, 129). Dr.
Stephen Slade, a refractive surgeon, summarized the procedure well by saying,
“PRK works well, but it hurts and the results take too long. To be honest,
patients don’t like it.” Soon after PRK was introduced, surgeons began testing
a procedure called Laser In-Situ Keratomileusis, which was first partially
introduced by the father of ophthalmology, Barraquer in 1950 (Slade, 8).
Keratomileusis is derived from the Greek root keras (horn-like cornea) and
mileusis (carving) and basically it is a procedure that involves slicing and
peeling back the outer layer of the cornea (anterior cornea), leaving a hinge
on one side, while the laser sculpts the tissue underneath (corneal stroma).
After the excimer laser is done, the flap is placed back to where it was
before, and no stitches are needed because the corneal flap heals by itself
when left to dry. You are probably wondering if they still used the diamond
scalpel, and the answer thankfully is not. Surgeons use a very precise
instrument called the microkeratome (See Figure 3) which makes LASIK very
unique compared to other surgeries. This device is a mechanical shaver that
has a sharp blade, which moves back and forth at very high speeds (See figure
2). After a suction ring has been placed on the cornea, the microkeratome is
place on top of the cornea and advances across it at very small increments
creating a flap that is only 1/3 inch in diameter. This instrument cuts the
cornea at a uniform thickness and creates a portion of the cornea uncut. After
the suction ring and the microkeratome have been removed, the corneal flap is
folded back (See Figure 4), exposing the middle portion of the cornea. Also in
LASIK surgery, the excimer laser can be used at different frequencies and
therefore produce different desired results in the same patient. Each laser
pulse in a LASIK procedure removes ten-millionths of an inch of corneal tissue
in twelve-billionths of a second while in a PRK procedure, the laser removes
about twice as much in about the same time. The amount of corneal tissue
removed depends on how nearsighted or farsighted the patient is (Gorman, 60).
The more nearsighted a patient is the more tissue must be removed to obtain a
flatter cornea, and the same goes with farsightedness, except the cornea has
to be made steeper. Back when Barraquer started Keratomileusis In Situ, he
noticed that he was having great success with patients who had myopia and did
not know why patients who had hyperopia and astigmatism were not enjoying the
same results. Surgeons even today notice, that after LASIK, patients who have
myopia before the surgery get better results than patients who have other
vision ailments (such as hyperopia, astigmatism, and presbyopia) (Gallo, 128).
Ophthalmologists now believe that the reason has to do with how the excimer
laser reshapes the cornea (Gallo, 128). In a patient who has myopia, the laser
makes the cornea flatter while in a hyperopic situation, the laser makes the
cornea steeper. The problem does not come during the surgery but after it when
the cornea bed reshapes itself to match the “new” cut cornea. They call it the
cornea bed because it is just like a bed because as you lie on a mattress, it
will reshape itself to the contour of your body. Once the cornea is made
flatter, the cornea bed has no problem reshaping itself to the new contour;
however, this is not always the case for hyperopia and astigmatism. The
corneal bed, which is located behind the outer layer of the cornea, has
trouble reshaping itself to either a steeper or narrower shape.
Ophthalmologist do no fully understand why this occurs, but they do urge that
LASIK provides better results for people who suffer from myopia and therefore,
that is why the vast majority of people who undergo LASIK do so to correct
nearsightedness (Buratto, 9). The results of LASIK are astounding (Gallo,
129). The obvious goal of LASIK is to get a vision of 20/20, which is perfect
vision. 20/20, 20/40, and so on are measures of visual acuity; a person with
20/40 needs to stand twenty feet away from something that a person with 20/20
can see fine from forty feet away. Last March, the Journal of Ophthalmology
stated that 3 months after the surgery, seventy-percent of the patients who
have had LASIK, have 20/20 vision. A follow up 2 years after the surgery
showed that sixty-three-percent kept the “perfect vision” while
ninety-nine-percent had at least 20/40 vision. The amount of vision
improvement generally is tied to the degree of nearsightedness and
farsightedness before the surgery. Dr. Stephen Slade, who is one of the
pioneers of LASIK said, “The less nearsighted or farsighted you are, the more
likely you’ll get 20/20. For low myopes, ninety-five percent can get 20/20.
For high myopes, the figure might drop to sixty percent.” Usually, for every
good thing that comes along, there are some unfavorable circumstances that
follow; however, there are not too many complications or side effects in LASIK
(Shovlin, 113). Complications are very rare, but they will be more common in
patients with high nearsightedness, farsightedness, and astigmatism because
they require more laser treatment. Also no patient has ever become blind after
a LASIK procedure; however, there are a list of possible complications that
can result in decreased vision after the surgery. One complication results
from the anterior cornea (flap) being placed unevenly after the laser
treatment, which usually results in a corneal haze. Another possible
complication is that of an infection, which only occurs in .5 percent of the
time. However, by far, the most common complication is under or over
correction, which are due to the laser removing either too much tissue or too
little tissue respectively. Under correction results from lack of corneal
tissue being removed and is usually fixed with a procedure called “touch up”
(another mini LASIK procedure but without any further cuts). If too much
corneal tissue is removed, the problem is a lot more serious because surgeons
must perform a Keratophakia, in which they have to add corneal tissue. Under
correction and over correction are the main reasons that all patients do not
receive 20/20 vision, and that is why no patient can ever be guaranteed
perfect vision. Last January, a review in LASIK of 1,062 eyes found that
complications occur in about 5 percent of the cases. Tests before the
procedure are now being taken more seriously than before, because those tests
determine how much laser treatment is needed. While the recovery period of
LASIK is remarkably short, forty-percent of people who had the procedure see
halos or starbursts around bright lights for several months (Buratto, 5).
Ophthalmologists believe this effect seems to be caused by the edge created
between the treated and the untreated part of the cornea which bends and
distorts the light as it enters the eye. Seeing halos or starbursts usually
occurs during night, when the pupil dilates and the edge of the cornea falls
right into view and for this reason, people with exceptionally large pupils
should not undergo LASIK. These starburst effects, as ophthalmologists call
it, usually go away after a few months. Little research is available on
LASIK’s long-term safety and effectiveness, but there is information available
on PRK. Last year, a review in ophthalmology traced eighty-three British
patients who underwent PRK in 1990, and found no serious complications in any
of them. This is attributed to the amount of untouched, deep cornea
(approximately fifty percent of the entire cornea), which maintains the eyes
original overall shape. This is opposite of RK which left only 10% of the
untouched cornea (Voelker, 1494). Despite its increasing popularity, LASIK is
not for everyone. People with extra-thin corneas are not good candidates of
this surgery because the surgeon does not have enough tissue to work with.
Ophthalmologists also turn away people who have rheumatoid arthritis and
diabetes because they have problems with dry eyes, and are hence poor healers.
As people approach forty years old, they begin to lose the ability to change
their focus from far to near (presbyopia), but don’t worry, it is natural in
everyone. Baby boomers who have LASIK to try to correct presbyopia, usually
trade their distance glasses in for reading glasses (or vice versa). Surgeons
are now answering this problem with “mono-vision”, which is correcting one eye
for far distance and the other for focusing on close distances. After this
procedure, the brain adapts, using each eye for different functions; however,
patients often experience blurry midrange vision and have depth perception
problems. “Most patients don’t mind it, but it drives some people nuts,” says
Dr. Slade. “There is a revolution happening in vision correction,” says Dr.
Guy Kezirian, a refractive surgeon in Arizona, and spokesman for the
International Society of Refractive Surgery. “We’re seeing a stampede of
people interested in a surgical alternative.” The question I ask is, why not?
Glasses can be very inconvenient, and contacts can be a hassle, so why not
venture in this vast, growing field of LASIK? LASIK is not just an eye
operation anymore, it is a 2 billion dollar a year industry that has
revolutionized the way surgery is looked at. Usually costing two thousand
dollars per eye, LASIK is not a surgery that anyone can afford, especially
since it is not covered by insurance. Yet when asked, a LASIK patient
consistently states that the surgery was one, if not the, best thing which
they have ever done for themselves: no worries of sleeping with contact lenses
and contracting a sight threatening infection (Slade, 254). No fear of scuba
diving or swimming with contacts, and no fear of waking up 3 a.m. after having
heard noises downstairs, and not being able to find your glasses. LASIK
surgery gave Diane, a forty-five-year-old doctor assistant, a newfound sense
of freedom. Before the surgery, she couldn’t clearly see her feet when she was
in the shower, but now after LASIK, she is taking rock-climbing lessons with
her twelve-year-old daughter; something she would have never done if she were
wearing glasses or contacts. Stories like this are becoming common as
Americans flock to eye doctors at record rates for this “surgical fix”. LASIK
is blossoming like a flower in the Fertile Crescent and soon everybody will be
taking advantage of its wondrous gift that it provides; the gift of sight.
_Bibliography _
WORKS CITED (REFERENCE PAGE) 1. Bull, Edward. LASIK Surgery. (Online)
Available http://zyworld.com/Phidelt738/Lasik-pg1.htm. November 13, 1999 2.
Buratto, Lucio. “Eyes Wide Open About LASIK.” Harvard Health Letter. 25,
October, 1999: 1 3. Caster, Andrew M.D. The Eye Laser Miracle. Toronto:
Ballentine Books, 1997 4. Gallo, Nick. “No More Glasses!” Better Homes and
Gardens. 77, October, 1999: 126-130 5. Gorman, Christine. “R U Ready to Dump
Your Glasses? Laser Surgery Can Work Wonders.” Time. October 11, 1999: 58-66
6. Shovlin, Joseph. “A Glaring Problem after LASIK.” Review of Optometry. 136,
October 15, 1999: 113-114 7. Slade, Stephen. Machat, Jeffery. Probst, Louis.
The Art of LASIK. New Jersey. SLACK Inc., 1999. 8. Sloat, John. “Here Comes
the Hyperopes.” Review of Optometry. 136, October 15, 1999: 89-93 9. Voelker,
Rebecca. “New Techniques Resculpt the Cornea.” JAMA (Journal of the American
Medical Association). 274, November 15, 1999: 1493-1498
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