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Conductive keratoplasty
(CK):
Non-Invasive Eye Surgery for
Hyperopia and Presbyopia
Conductive keratoplasty (CK)
is a relatively new type of
refractive surgery that uses
mild heat from radio waves
to shrink the glue-like
connective tissue (collagen)
in the periphery of the
cornea.
This steepens the cornea,
giving farsighted patients
with presbyopia better near
and distance vision while
improving near vision for
patients with presbyopia
alone.
If you are nearsighted, CK
is not for you, although
expanded indications such as
for astigmatism correction
are being studied.
Better surgical techniques
and technology now address
earlier problems with CK in
that some corneas tended to
revert to original states
and vision corrections
failed to remain stable
(regression). With recent
clinical studies revealing
more stable results, CK is
gaining wider acceptance
among eye surgeons and
patients.
Long-term data ultimately
will determine whether CK's
results will be comparable
to other vision correction
procedures such as LASIK.
CK technology exclusively
belongs to Refractec Inc.
(Irvine, Calif.), which
markets the system under the
trade name of Refractec
ViewPoint CK. The Wall
Street Journal estimates
costs of CK vision
correction per eye to be
between $1,500 and $2,000,
and a physician investment
in the system to be about
$50,000.
A similar technology known
as laser thermal
keratoplasty (LTK), on the
other hand, appears to have
faded away. The Hyperion LTK
system had been sold by
Sunrise Technologies
International Inc., Menlo
Park, Calif., which filed
for bankruptcy in 2002 after
initially receiving FDA
approval to market the LTK
system in 2000 for temporary
reduction of hyperopia. The
FDA approval also noted the
tendency for patients
treated with LTK to
experience regression.
LTK used laser-based
technology to achieve
shrinkage of collagen,
whereas CK uses radio waves
applied at deeper levels
within the cornea to achieve
more lasting thermal
effects. The main advantage
of CK is that it is
non-invasive. Unlike LASIK,
CK does not involve knives
or lasers cutting into
ocular tissue, nor is any
instrument inserted into the
eye. Therefore, CK tends to
cause fewer surgical
complications than other
refractive procedures.
CK, the Radio Waves Eye
Surgery
Conductive keratoplasty
received FDA approval in
April 2002 for people 40 or
older with mild
farsightedness. In 2004,
expanded FDA approval
included presbyopia, a
condition that develops
beginning about middle age
in which your eye's natural
(crystalline) lens stiffens
and can no longer focus at
near, middle, and distant
ranges at the same time. CK
correction for presbyopia
differs from hyperopia in
that only one eye (the
non-dominant eye) is
corrected for near vision,
while the other eye is left
untreated.
After someone with
presbyopia receives CK, the
treated eye is able to see
at near ranges, while the
untreated eye sees at middle
to distant ranges.
Candidates for this type of
vision correction, known as
monovision, may be asked
first to wear contact lenses
for near vision correction
to make sure they are able
to adapt. But this is not a
requirement. The eye surgeon
instead might hold a +1.00
lens for near vision
correction in front of the
non-dominant eye to see if
the person experiences
significant distance blur at
a distance with both eyes
open. People who do not have
blurry distance vision under
these circumstances likely
are very good candidates for
CK.
CK offers a major advantage
in that the procedure is
less likely to blur distance
vision with monovision
correction than contact
lenses or laser vision
correction.
CK uses heat from radio
frequency waves to shrink
collagen and change the
shape of the cornea. The
surgeon uses a hand-piece
containing a tiny,
pen-shaped probe
(Keratoplast Tip) that
releases the frequency over
the periphery of the cornea.
The procedure takes about 15
minutes.
To qualify for CK correction
of hyperopia, you must be 40
or older and have between
+0.75 and +3.25 diopters of
refractive error, with no
more than 0.75 diopters of
astigmatism. Also, your
glasses or contact lens
prescription cannot have
changed within one year
before the surgery.
To make sure CK correction
of presbyopia is right for
you, your eye surgeon may
test you with a trial period
of wearing monovision
contact lenses in which one
eye is corrected for near
vision and the other eye is
corrected for far vision.
Or, the surgeon may
determine if you are a good
candidate for monovision
correction by holding a test
lens in front of your
non-dominant eye to make
sure your distance vision
remains sharp. [Read more
about monovision with
contact lenses.]
CK treatment parameters for
presbyopia allow induction
of myopia in the eye being
corrected for near vision
between a range of -1.00 to
-2.00 diopters. As with
hyperopia correction, your
glasses or contact lens
prescription cannot have
changed within one year
before the surgery.
Note also that FDA approvals
indicate that CK corrections
at this time are temporary,
although recent improvements
in surgical technique appear
to be stabilizing outcomes.
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