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About Lasik
Common
Vision Problems
Vision
Correction Techniques
Excimer
Laser Treatment -- Lasik,
IntraLasik, PRK,
and LASEK
Corneal
Rings (Intacs)
Holmium
Laser (LTK) and Conductive Keratoplasty (CK)
Implantable
Contact Lenses
Radial
Keratotomy (RK)
Astigmatic
Keratotomy (AK)
Automated
Lamellar Keratoplasty (ALK)
Excimer
Laser Treatment -- Lasik,
IntraLasik, PRK,
and LASEK
The excimer laser makes pulses of invisible ultraviolet light. Each
pulse of light removes a microscopic layer from the front surface of the
cornea, changing the curvature of the cornea ever so slightly.
To correct nearsightedness, the curvature of the cornea must be decreased
-- the cornea must be made flatter. To correct farsightedness, the curvature
of the central cornea must be increased. To correct astigmatism, the curvature
must be altered in one specific direction.
Only a very small amount of tissue is removed, usually less than the thickness
of a hair. Low amounts of nearsightedness, farsightedness, or astigmatisim
will require smaller amounts of tissue removal, and larger corrections
will require greater amounts. The total treatment usually takes less than
one minute of actual laser time.
A computer running specialized software determines the exact pattern of
pulses needed to remove the right amount of corneal tissue. The computer
also directs the actual operation of the laser system.
There are several variations of laser vision correction, each of which
has advantages and disadvantages. We are happy to treat you with the method
of your choosing. We will discuss your specific situation after we have
taken your personal history and performed measurements and calculations.
Each of these variations involves using the identical laser to correct
the vision. The difference is in the type of flap that is made, prior
to using the excimer laser.
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Lasik
(laser in-situ keratomileusis). This is our most common type of treatment.
A flap is made using an instrument known as a microkeratome. The laser
energy is then applied under the flap. Lasik allows for the most rapid
visual recovery. If you desire, both eyes can be treated at the same
time.
-
IntraLasik
(all-laser Lasik). The flap is created with the Intralase laser. The
vision is then corrected using the excimer laser. The visual recovery
is slower than with standard Lasik, though both eyes can be treated
at the same time.
-
PRK
(photorefractive keratectomy). No flap is made. The soft material
on the surface of the eye is removed with a brush, or with an alcohol
solution, and the laser energy is then applied to reshape the eye.
A contact lens is worn for 5-7 days while the soft material regenerates.
Only one eye is usually treated at a time; the other eye is usually
treated in 2-4 weeks.
-
LASEK
(laser epithelial keratomileusis). For patients with relatively thin
corneas, large pupils, very high corrections (or a combination of
these), LASEK may allow for the largest treatment size, which may
be important in diminishing glare and halos. A very thin flap is made
involving only the soft material that coats the front surface of the
eye. The laser energy is then applied under the flap. This ultra-thin
flap heals in 5-7 days, during which time the vision is blurry. Only
one eye is usually treated at a time; the other eye is usually treated
in 2-4 weeks.
Results
The vast majority of patients no longer need glasses or contact lenses
for distance vision after excimer laser treatment. Almost all patients
who have excimer laser treatment see better without glasses after the
procedure.
After
the initial treatment, 90% of patients will have 20/25 or better vision
without glasses, and 99% will have 20/40 or better vision without glasses.
20/40 vision is good enough to pass the driver's vision test without glasses.
For patients with mild nearsightedness, farsightedness, or astigmatism,
the results are even better. Patients requiring higher amounts of correction
will have less accurate results. The general rule is: more accurate results
will be obtained in people who require less treatment.
If needed, the results can be further improved through a repeat excimer
laser procedure. There is no additional fee to have a "touch-up"
procedure. We perform "re-treatments" in 7% of our patients.
These results are very impressive, but it is impossible to tell you exactly
what your results will be. No guarantees can be made about the outcome
of excimer laser surgery in any individual case, because each person responds
in a slightly different way. If you will only be satisfied with "perfect"
20/20 vision without glasses after excimer laser surgery, then please
do not have the surgery. Avoid any doctor or clinic that promises you
a specific result, because that simply is not possible.
The quality of vision after excimer laser treatment is usually superior
to vision with contact lenses or glasses. Patients generally have less
glare than they had with contact lenses, and of course the inconvenience
and discomfort of contact lenses is eliminated. Side vision isn't blocked,
as it is with glasses, and there is no longer the problem of dirty, wet
or scratched glasses.
Complications
Excimer laser treatment is subject to complications, but the complication
rate is very low. Complications are rare, but will be more common in patients
with high amounts of nearsightedness, farsightedness, or astigmatism,
because these patients require larger amounts of treatment. Most complications
can be partially or totally corrected through a repeat laser procedure.
By far the most common complication of excimer laser treatment is under-correction
or over-correction. These complications occur because the patient experiences
an abnormal healing response, or because slightly too much or too little
tissue is removed from the surface of the cornea. Further laser treatment,
known as an "enhancement" or a "touch-up", can then
be used, usually resulting in excellent vision without glasses or contact
lenses.
Under-corrections
and over-corrections are the main reason that all patients do not have
perfect uncorrected vision after the initial excimer laser treatment.
About
2% of excimer laser patients will experience optical aberrations, including
glare, halos at night, or ghost images. This occurs if light is entering
from around the edge of the treatment area. Some people have pupils that
dilate more than the treatment area. Use of the Alcon LadarVision
laser, with its eye tracker and substantially larger treatment areas,
has dramatically improved this problem.
Complications affecting the health of the eye are extremely rare, but
are possible. During the early healing phase, the eye is susceptible to
infection. You will be asked to follow certain instructions, including
using antibiotic eye drops. Carefully following these instructions will
decrease the infection rate to far below 1%. Even if an infection does
occur, use of antibiotic eye drops will almost always control the infection.
Steroid eye drops are very important after excimer laser treatment, because
they are used to control the healing response. However, if used improperly
for too long, these drops can damage the eye by causing cataracts or glaucoma.
It is very important to go to all scheduled follow-up appointments, especially
if you are still taking steroid eye drops.
About 1% of excimer laser patients experience some loss of best-corrected
vision, which is the best vision possible when using glasses or contact
lenses. About 2% of patients will experience an improvement in the best
corrected vision. Of course, you probably will no longer use glasses or
contact lenses for distance vision after the surgery, so you may not even
be aware that your best possible vision is different.
Some professionals, such as commercial and military airplane pilots, care
very much about their best-corrected vision. These pilots must have best-corrected
vision of 20/20 in both eyes. If the best-corrected vision is anything
but a perfect 20/20, the pilot's license will be lost.
A mild loss of best-corrected visual acuity might not even be noticed
or might be just a minor annoyance. A severe loss of best-corrected visual
acuity would be noticed by almost every patient and might make it hard
to work in occupations that require fine vision. Severe losses of best-
corrected visual acuity are exceedingly rare.
Either an irregularity or a haziness in the corneal surface could cause
a decrease in best-corrected vision. Short-term irregularities during
the initial months of healing may occur in up to 5% of cases and almost
always resolve as the healing progresses.
Re-treatments
Not all patients get a satisfactory result from excimer laser treatment.
This may be due to under-correction, over- correction, or one of the complications
described above. The most common problem is an abnormal healing response,
resulting in under-correction or over-correction.
Patients who experience under-correction or over-correction can usually
undergo a second procedure to obtain a better correction. In most cases,
a significant improvement in the vision will occur, but it is important
to realize that this, too, is a laser procedure, and therefore has the
same risks that the first laser procedure had. It is possible but extremely
rare that your vision can be worse after a "touch-up" procedure.
Complications can occur, even if no complications occurred during your
first procedure.
If your vision is quite good after your excimer laser treatment, but not
perfect, you should consider carefully whether you want to have a "touch-up"
procedure. If your vision is really not satisfactory, then a "touch-up"
procedure is a good idea. Overall, 7% of our patients undergo "touch-up"
procedures, though this will vary significantly from surgeon to surgeon.
Which laser treatment is best for me -- Lasik, IntraLasik,
PRK, or LASEK?
The original form of excimer laser treatment is known as PRK (for "photo-refractive
keratectomy"). In PRK, the thin layer of soft tissue coating the outside
of the eye is removed and the laser energy is applied to the superficial
tissue underneath. In LASEK--with an "E"--a thin flap is made using the
soft tissue on the surface, and the laser is then applied to the superficial
tissue underneath. LASEK is therefore very similar to PRK.
The most popular variation of excimer laser treatment is called Lasik
(for "laser in-situ keratomileusis"). In this technique, the laser applications
are made deeper within the cornea, rather than near the corneal surface.
This is accomplished by creating a flap in the front 20-30% of the cornea
and then applying the laser treatment to the tissue beneath the flap.
This flap can be made with a special laser, in which case the procedure
is known as IntraLasik.
When the laser treatment is applied to the tissue deep within the cornea
instead of to the surface, the healing response is lessened, which greatly
speeds up the vision recovery period. Patients usually see quite well
the next day after Lasik or IntraLasik, as opposed to waiting several
weeks with PRK or LASEK..
Most of the pain fibers in the cornea are in the surface portion. Because
this portion of the cornea is removed in PRK but not in Lasik (it is part
of the flap, which is folded back into place after the laser energy is
applied), there is much less discomfort after Lasik.
Lasik requires an additional surgical step, which is the creation of the
flap. The flap is created with an instrument known as a keratome, which
cuts and then folds back a thin layer of the front of the cornea. Creation
of the flap takes about 15 seconds and is virtually painless. When the
flap is made with the laser (IntraLasik), it takes about two minutes.
The return of vision is slightly slower when IntraLasik is used.
Complications with the flap occur about 1% of the time. Almost all of
the complications are mild and can be easily treated, often by lifting
or repositioning the flap. The most serious complication would involve
improper creation of the flap; when this occurs, the patient is asked
to wait three months, and then can return for a repeat treatment.
We perform all four variations of laser vision correction -- Lasik, IntraLasik,
PRK, and LASEK. During your initial consultation, we will talk to you,
obtain measurements of your eyes, and determine which procedure is the
best for your specific situation. Lasik is usually our procedure of choice.
Patients greatly prefer the Lasik procedure in terms of rapid vision recovery
and decreased pain. The vision recovery with Lasik is so rapid that most
of our patients return to work the very next day.
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Corneal
Rings (Intacs)
Corneal rings (also known as Intacs, intrastromal corneal rings, or ICR)
are small pieces of plastic that are embedded in the edge of the cornea.
The arc-shaped rings make the central portion of the cornea flatter, decreasing
the amount of nearsightedness. Currently, corneal rings are available
to treat only low amounts of nearsightedness, and treatments for astigmatism
and farsightedness are still being developed.
By using rings of varying thickness, different amounts of nearsightedness
can be corrected. However, corneal rings are made in only a very limited
number of thicknesses, so they can only be used for very specific corrections.
If the visual result is not ideal, or if the eye changes in the future,
the corneal rings can be removed, but there might not be another ring
that is appropriate to correct the vision. In contrast, excimer
laser treatments are available for a wide range of focusing errors and
are easily adjustable with retreatments.
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Holmium
Laser (LTK) and Conductive Keratoplasty (CK)
Farsightedness is the result of too little curvature of the cornea. In
order to correct farsightedness, the central cornea must be made steeper.
With the excimer laser, the central cornea is made steeper by removing
tissue in a doughnut-shaped pattern from the peripheral cornea.
Another type of laser, known as the holmium laser (manufactured by Sunrise
Technologies), is also currently available to treat farsightedness. The
holmium laser produces infrared light, which causes tissue to constrict,
and is therefore very different from the ultraviolet excimer laser. The
excimer laser reshapes the cornea by removing tissue; the holmium laser
reshapes the cornea by causing tissue to constrict.
To treat farsightedness, the holmium laser is applied to the periphery
of the cornea in a pattern of multiple spots. As this peripheral tissue
constricts, the central cornea steepens, resulting in a decrease in farsightedness.
This technique, known as LTK (laser thermal keratoplasty), is effective
in reducing lower amounts of farsightedness.
However, the results of LTK are frequently not permanent; commonly, a
very substantial loss of effect will occur over the first two years, and
the procedure will need to be repeated. For this reason, we will only
very rarely recommend this technique.
A similar technique, known as or radio frequency keratoplasty (RFK) or
conductive keratoplasty (CK), uses radio frequency energy to constrict
the tissue. CK has been approved by the FDA to treat low amounts of farsightedness
(hyperopia), though astigmatism cannot yet be treated.
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Implantable
Contact Lenses
Intraocular implants, also known as implantable contact lenses or phakic
intraocular lenses, are tiny plastic lenses inserted inside the eye, behind
the cornea. These lenses bend the incoming light rays and can correct
nearsightedness, farsightedness, and astigmatism.
Intraocular implants have been used successfully for many years to the
replace the crystalline lens when it turns cloudy -- forming a cataract
-- and has to be removed. When used to treat nearsightedness, farsightedness,
or astigmatism, intraocular implants are placed in front of the crystalline
lens, and the crystalline lens is left inside the eye. Some implants are
placed in front of the iris (the colored part of the eye) and are known
as anterior chamber implants. Others are placed behind the iris and are
referred to as posterior chamber implants.
The long-term safety of intraocular implants for nearsightedness, farsightedness,
and astigmatism has not been determined and extensive tests are currently
underway. Because they are placed near critical structures inside
the eye, there is concern that they may cause cataracts or glaucoma. If
determined to be safe, intraocular implants may be used to treat people
with too much nearsightedness or too much farsightedness for the Lasik
technique.
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Radial
Keratotomy (RK)
Radial keratotomy was the first surgical procedure to be widely used to
correct nearsightedness and, contrary to most people's understanding,
does not involve the use of a laser. RK was invented in the Soviet Union
in 1973 and was first performed in the United States in 1978. Over one
million people around the world have been treated with RK.
Like excimer laser surgery, RK corrects nearsightedness by altering the
shape of the cornea. The doctor makes a series of incisions in the periphery
of the cornea. This increases the corneal curvature slightly where the
incisions are made, and decreases the curvature in the central portion
of the cornea. The incisions are made in a radiating pattern, like the
spokes on a bicycle wheel. By varying the number, length, depth, and location
of these incisions, different amounts of nearsightedness can be corrected.
Although patient satisfaction with RK was very high, RK has now been largely
replaced by excimer laser techniques and is seldom used today. Lasik and
PRK produce results that are more accurate than RK and can treat a much
wider range of focusing errors. Because of this greater accuracy, excimer
laser patients are much less likely than RK patients to require a "touch-up"
procedure. Also, RK patients experience side effects more commonly than
do excimer laser patients. These side effects include "starbursts" when
viewing a bright light against a dark background and fluctuation in vision
throughout the day. RK patients, but not excimer laser patients, experience
a temporary, reversible fluctuation in vision when at high altitudes.
Pilots, mountain climbers, and skiers may be affected by this and should
not have RK.
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Astigmatic
Keratotomy (AK)
Astigmatic keratotomy is a variation of RK, used to treat astigmatism.
AK uses arc-shaped incisions in the cornea, whereas RK uses radial incisions,
like the spokes of a wheel. Neither RK nor AK is performed with a laser.
At the Caster Eye Center, we do not perform RK or AK.
AK is often performed in conjunction with RK and can also be performed
in conjunction with excimer laser surgery. This is important, because
not all excimer lasers can correct astigmatism, so excimer laser treatment
of nearsightedness and farsightedness is occasionally combined with AK
treatment of astigmatism. For mild or moderate astigmatism, AK's predictability
is good but certainly not perfect. In most cases, it is more accurate
to treat astigmatism with the excimer laser than to use AK.
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Automated
Lamellar Keratoplasty (ALK)
Performed from the 1970s until the mid-1990s, ALK was the forerunner to
Lasik. In ALK, a keratome was used to peel back the front layers of the
cornea, creating a flap, just as it is used in the Lasik procedure today.
No tissue is permanently removed in the making of the flap; by making
the flap, it enables the doctor to work on the deeper tissue of the cornea.
In ALK, the keratome was then used a second time to remove a small disc
of cornea from under the flap, causing the central cornea to flatten and
lessening nearsightedness. In Lasik, the tissue under the flap is instead
removed using the excimer laser, which is much more precise.
ALK has been completely replaced by Lasik and is not performed anymore.
In fact, ALK was never very popular because the second part of the procedure,
removing the disc of tissue, was not adequately precise. However, without
ALK we would probably not have Lasik today. Lasik is a combination of
the flap technique of ALK with the precision of the excimer laser -- a
truly remarkable combination.
Because ALK has been performed since the 1970s, we have a long track record
showing the safety of making corneal flaps. This is very important: because
of ALK, we know that there are no long term safety problems from making
corneal flaps.
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