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LASIK & PRK
The cornea and lens combine to focus visual images on the retina,
in the back of the eye. When the overall shape of the eye is
incorrect or when the curvature of the cornea is incorrect, the
visual images are not in focus. The cornea accounts for
approximately two-thirds of the focusing power of the eye. By
surgically changing the corneal curvature, the image can be
placed clearly in focus on the retina with most or all of the
blur eliminated.
Laser In Situ Keratomileusis (LASIK) and the
older Photo-Refractive Keratectomy (PRK) are two surgical
techniques which utilize lasers to reshape or change the
curvature of the cornea.
LASIK
LASIK had its origins about thirty years ago and was originally
developed to treat patients who had very poor vision due to
corneal disease. It has now evolved into a successful technique
for correcting refractive errors. The current procedure, done on
an outpatient basis, involves both the use of conventional and
laser surgery to correct nearsightedness, farsightedness and
astigmatism. LASIK can correct a much higher degree of
nearsightedness, with or without astigmatism, than any other
refractive procedure, with excellent results. Current data
indicate that 99.7% of patients maintain best corrected visual
acuity of 20/20 or better.
The LASIK Procedure
In performing LASIK, eye drop anesthetic is used to numb the eye.
The surgeon then uses a special instrument called a
micro-keratome to cut into and behind a layer of the cornea. A
portion of the cornea is lifted back to create a flap and expose
the inner portions of corneal tissue. The eye is then positioned
under the excimer laser, which has been computer programmed to
remove microscopic amounts of the internal corneal tissue.
Removal of the tissue changes the curvature of the cornea.
Infrared tracking technology is currently being used which allows
the computer to adjust the treatment for any tiny movements of
the eye during the laser treatment. This allows for more safe and
accurate outcomes.
If the patient is nearsighted, tissue closer to the central part
of the cornea is removed to decrease the curvature and
effectively flatten the cornea. If a patient is farsighted,
tissue in the peripheral part of the cornea is removed to
increase the curvature of the cornea. To correct for astigmatism,
selected tissue at certain angles is removed to ensure that the
cornea curves equally in all directions.
After the laser has been used, the flap is returned to its
original position. The corneal tissue has extraordinary natural
bonding qualities that allow effective healing without the use of
stitches.
Since only local anesthetic is used, patients remain awake during
the procedure. The entire procedure takes only a few minutes.
Improved vision is often possible on the day following the
surgery. After surgery, eye drops are prescribed, and it is be
necessary to wear protective eye goggles, like sport goggles, at
night for approximately one week.
Advantages of LASIK:
The advantages of LASIK include a much faster healing time than
other refractive surgical methods, rapid visual recovery, less
risk of scarring, less risk of corneal haze, and less post-op
discomfort. As a flap is created during LASIK surgery, flap
management is an additional consideration.
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Photo-Refractive Keratectomy
(PRK)
Photo-Refractive Keratectomy, or PRK, is another method of
surgically reshaping the cornea using the excimer laser. The
difference between LASIK and PRK is that for PRK, a corneal flap
is not created. That is, the outer layer of the cornea remains in
place and the laser removes tissue directly from this outer
layer. PRK is used for low to moderate amounts of
nearsightedness.
Just as in LASIK, the laser treatment for
PRK requires only a few minutes. But unlike LASIK, the healing
period takes longer, there is greater discomfort, more
medications are used for a longer period of time, and the time to
visual recovery is prolonged. The correction for nearsightedness,
farsightedness, and astigmatism is the same as in LASIK. The
majority of refraction surgeons prefer to perform LASIK over PRK
except in instances of thinner than normal corneas or when there
is a question relating to optic nerve health.
Intra Ocular Lenses (IOLs) for Refractive
Surgery or Implantable Contact Lens (ICL)
When the eye is unable to properly focus, the
result is blurry vision. One option to correct for this is IOLs
(Intra Ocular Lenses). IOLs have been used for many years to
replace the natural lens during cataract surgery. IOLs for
refractive surgery differ significantly from other refractive
methods in that they do not involve changing the shape and/or
structure of the cornea (the clear outer layer of the eye). IOLs
replace the natural lens (phakic lens) of the eye and can correct
for significant refractive errors, which can greatly enhance
vision.
Phakic IOLs are ideally suited for individuals who are poor
candidates for other refractive options, such as LASIK. This
includes those with high refractive errors, including myopia
greater than -10 diopters and hyperopia greater than +4 diopters.
In addition, phakic IOLs are also an excellent choice for those
with keratoconus, those who have thin corneas, or for those who
are no longer able to tolerate contact lenses or eyeglasses.
The IOL Procedure
Inserting a phakic IOL is a nearly identical process to the lens
implantation portion of a cataract procedure. Before surgery, an
extensive set of eye tests are taken to determine the proper
power of the lens to be inserted. The actual procedure is then
performed through a small incision in the cornea. In some cases,
tiny foldable IOLs can be inserted through a smaller incision
(1/8 of an inch wide). Once inside the eye, these lenses unfold
into a full-sized IOL. The advantage of the small incision
approach is improved safety and faster recovery of vision after
surgery.
The Intra Ocular Lens is implanted between the
iris and the front surface of the human lens. IOLs are made of
the same plastic as certain types of contact lenses. The
procedure is typically performed with a general or topical
anesthetic.
Health Issues Associated with Phakic
IOLs
As with any surgery, complications are rare but do exist. The
main drawback to IOLs is that, unlike other refractive surgery
options, the incision and procedure is performed inside the eye
(as opposed to on the surface). The nature of this surgery
carries heightened risks for internal eye infection or damage. A
consultation with your Ophthalmologist or surgeon can address
potential health complications.
Because the 'IOLs for refractive surgery'
procedure is a reversible process, it offers an advantage over
some other procedures. If the results are less than optimal, the
patient can choose to have the IOLs surgically removed. IOLs
typically last forever. Unlike other refractive surgery options,
IOLs do not weaken the strength or integrity of the eye.
Intacs
Nearsightedness is an
extremely common condition in which the curvature of an
individual's cornea is too steep to properly focus light onto
the retina. Intacs (Intrastromal Corneal Ring Segments) are a
safe, easy, non-laser alternative for correcting mild
nearsightedness. Intacs are extremely thin, crescent-shaped
plastic polymers that, when implanted in the eye, restore the
cornea to its ideal curvature, resulting in clear, focused
vision.
An initial consultation with a
refractive surgeon can determine whether or not a patient is a
good candidate. Intacs are ideally suited for individuals with
nearsightedness of -1.00 to -3.00 diopters and no more than 1.00
diopter of astigmatism. (A diopter is a measure of the power of
eyeglasses or contact lenses). Patients also need to have stable
vision and generally healthy eyes to qualify for
Intacs.
Prior to the insertion of Intacs, a small opening
is made at the very edge of the cornea. Two crescent-shaped
pockets or tunnels are made on the periphery of the cornea,
outside the central optic zone (the area where the main ocular
functions occur). These pockets are created between the layers of
the cornea (known as the stroma), and the Intacs are fitted
inside. The thickness of the Intacs depends on the amount of
flattening needed -- the thicker the Intac, the more flattening
occurs. Once the Intacs have been fitted inside the eyes, the
small opening is closed up.
Intacs essentially reshape the cornea, allowing it to maintain
its proper curvature. Anesthetic eye drops numb the eye to make
the short procedure virtually pain-free. The procedure lasts 15
to 30 minutes and is performed on an outpatient basis.
Following surgery, many patients return home and rest for the
remainder of the day. Improved vision typically begins to occur
within the first 24 hours. Intacs are designed to remain in the
eye permanently, although they can be surgically removed if the
need arises. They are about as easy to detect as a pair of
contact lenses.
Orthokeratology
It is estimated that roughly 30% of the U.S.
population suffers from nearsightedness, or difficulty seeing at
a distance. Orthokeratology (also referred to as Ortho-K or OK)
is an older, essentially outdated method of temporarily reshaping
the cornea with a rigid contact lens. It is rarely used
today.
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