Conductive Keratoplasty For
Presbyopia & Hyperopia
Can you discard your reading
glasses?
Let's
explore the relatively new, non-laser
procedure known as conductive keratoplasty
(CK), which was specifically developed to
reduce dependence on reading glasses as well
as to reduce dependence on glasses and
contact lenses for those affected by
hyperopia (farsightedness). CK is a
minimally invasive procedure that uses
radiofrequency to reshape the cornea. It is
performed using the ViewPoint CK System by
Refractec, Inc., and it is the only
FDA-approved technology for the temporary
improvement of near vision for those who are
presbyopic.
If you’re not certain if you have
presbyopia
or hyperopia, you may want to return to
click here for a more detailed
review. However, I’ll present presbyopia
again in this chapter because of its
importance to this subject matter.
Presbyopia and Reading Glasses
Presbyopia, indicated by one’s difficulty
with focusing on near objects, is a normal
characteristic of the aging eye. For those
over the age of 40, it is usually well
understood. There is difficulty with
focusing on near objects or comfortably
focusing on near objects for any length of
time.
Presbyopia occurs as the eye’s natural lens
gradually loses its elasticity, thereby
preventing accurate focusing on objects at a
near distance. Those with presbyopia may
experience eye fatigue with sustained
efforts of near focusing, such as reading a
newspaper. There may be even more
difficulties when attempting to read in dim
light. Finally, the problem tends to worsen
with each passing year beyond the age of
forty.
For those who are naturally myopic
(nearsighted), simply removing their
distance correction (glasses or contact
lenses) usually allows near focusing with
ease. Some individuals with
hyperopia
(farsightedness) discover their presbyopia
while in their 30’s because the eye has lost
enough natural focusing ability that the
hyperopia presents itself with blurring of
both distance and near acuity.
Treatment Options
for Presbyopia
Many individuals who discover their own
presbyopia simply resort to a pair of
“dime-store” reading glasses and this works
fine. There is no reason for concern over
the power of the glasses as they will do no
harm, however, I always advise patients to
keep the reading material at a fixed
distance and vary the reading glasses power
as they select their “readers”. Keep in
mind that, as the power of the glasses
increases, the focal point moves closer
indicating that the reading material (or
object of concern) must be moved closer as
well, in order to remain in focus.
Conversely, as the reading glass power
decreases, the focal length is farther away
and the reading material must be moved
farther away. In any case, just think of
“readers” like a magnifying glass… choose
whichever one you desire.
Other options for presbyopia include bifocal
or trifocal glasses and “bifocal” (actually
multifocal)
contacts. “Bifocal” type
contacts have not enjoyed tremendous
success, however, due to quality of vision
concerns and, of course, the need to wear
eyewear at all.
For those who desire not to wear any
correction at all, but who are already
presbyopic (age 40 and above), clinical
efforts have usually been directed toward
achieving distance vision in one eye and
near vision in the opposite eye. This type
of situation, known as “monovision” or
“blended vision”, has been utilized for
decades with contact lens wearing patients.
Once the patient’s dominant eye has been
determined, the non-dominant eye is usually
selected for the near vision treatment. For
those choosing a surgical option, such as CK
for monovision, a trial is usually completed
to allow the patient to experience
monovision. One eye can be temporarily
corrected for near using either temporary
glasses or a contact lens. If monovision is
well tolerated, the patient may elect to
undergo the CK procedure to give the
non-dominant eye near vision. The dominant
eye is left untreated as it will serve the
purpose of far distance vision.
The only surgical option for presbyopia that
is FDA approved is NearVision CKâ using the
ViewPointä CK system by Refractec. Any
other type of surgical procedure to enhance
near vision would be much more invasive and
carry far greater risk, in my opinion.
Examples of other surgical options would
include LASIK or PRK (both to make one eye
nearsighted), phakic intraocular lens
implants (see Chapter Twelve),
refractive lens exchange (see Chapter Thirteen), and
laser thermokeratoplasty (LTK), the latter
of these having been wholly abandoned due to
100% regression of effect[i],
[ii]. NearVision CKâ is safe – very
safe. I’ll review the details on safety
below.
Conductive
Keratoplasty (CK) for the Hyperope
If you refer back to Chapter Six, I gave a
refractive surgery decision algorithm that
presented CK as a procedure of choice for
individuals age 40 and above who have +1.0
to +3.0 diopters of hyperopia. In fact, the
Refractec ViewPointä CK system was evaluated
in multicenter controlled clinical trials
and received FDA approval for treatment of
hyperopia between +0.75 and +3.25 diopters,
with astigmatism up to 0.75 diopters. The
approval was specifically for individuals
age 40 and above in whom the refraction was
stable for the prior year[iii].
A newer method of CK, known as “Light Touch”
CK, has shown even greater promise to treat
those with hyperopia, even up to +3.5
diopters of power[iv].
In this method of CK, there is greater
effect with fewer spots placed on the cornea
and less pressure placed on the probe tip by
the operating surgeon. This also means that
surgeons may be able to treat more patients
with even greater degrees of hyperopia, with
less chance of induced astigmatism because
the treatment is farther from the center of
the cornea.How CK
Works
Conductive keratoplasty works because the
procedure results in steepening of a
relatively flat central cornea. “CK offers
a higher quality of vision with less night
vision symptoms,” says esteemed refractive
surgeon, Richard L. Lindstrom, M.D., chief
medical editor of Ocular Surgery News and
clinical professor at the University of
Minnesota[v].
“CK is not only a safe procedure, but it
also provides the patient with a larger
optical zone and a smooth blend. Research
suggests that CK creates an aspheric cornea
equipped with mild multifocality.” This
means that patients have significant
improvements in near vision {in patients
treated for
presbyopia} with minimal loss of
distance vision.
The Conductive Keratoplasty (CK)
Procedure
CK is a very quick procedure, requiring only
a few minutes per eye, and involves the
operating surgeon treating the peripheral
cornea with radiofrequency (RF) delivered
via a keratoplasty tip placed against the
eye in the proper anatomical position.
There is no cutting, no injections, and no
laser. First, the eye is anesthetized
with topical eye drop medications.
Next, a speculum is placed, which holds the
lids apart and prevents blinking. The
cornea is marked with rinse-away ink to
guide the plan of treatment. The
patient is asked to look at a fixation
light. Then, the operating surgeon
places a series of circumferential RF spot
applications, which follow the pre-placed
corneal markings. The
radiofrequency quickly, briefly, and in
controlled fashion, heats the corneal
collagen, which causes the collagen to
shrink and contract. This acts like a
purse-string, tightening the mid-periphery
of the cornea like a belt with resultant
steepening of the central cornea. This
reduces hyperopia, in the case of treating
farsightedness, or induces mild myopia
(nearsightedness), in the case of treating
presbyopia. A nomogram is utilized to
determine how many RF spots are required for
a given degree of correction.
According to refractive surgeon, Marguerite
B. McDonald, M.D., professor at Tulane
University in New Orleans, “approximately
80% of patients need only eight treatment
spots with CK with Light Touch”[vi].
Patients with greater degrees of hyperopia
may require 16, 24, or even 32 spots of RF;
the exact number being dictated by a
nomogram that is refined according to the
surgeon’s personal results.
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The CK
Procedure
This illustration shows the
keratoplasty tip being applied to
the cornea. In this depiction,
there are three rows of
radiofrequency (RF) spots indicated
by the pale white areas on the
cornea.
Illustration courtesy of
www.JirehDesign.com
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The Conductive
Keratoplasty Procedure
Once the CK procedure is finished, the
patient can usually leave the office with
instructions to use anti-inflammatory,
antibiotic, and sometimes dilute anesthetic
eye drop medications. Post-op
discomfort or pain is actually quite
unusual, however, when this occurs, the
topical medications and anesthetic agents
should easily control the discomfort.
Most patients can return to work and normal
activities the very next day.
Though almost half of patients have
excellent vision the next day, the other
half tend to have blurred vision that
gradually improves, typically regaining
excellent vision within two weeks. Some
patients will have fluctuations of vision
over several weeks or even several months
time.Retreatment…or
“Touch Ups”
CK does tend to have some degree of
regression of effect. As some surgeons have
stated, “CK can turn back the hands of time,
but it cannot stop it”. Dr. Marguerite
McDonald tells her patients that they will
most likely need a touch-up in about two
years time. For those being treated for
presbyopia, she states, “They must
understand that they will have a 90%
reduction in the use of their reading
glasses but not 100%, and it’s a tool that
they will have to get accustomed to using.”
There is probably only about 0.25 diopters
of regression of effect per year[vii],
which means that the CK treatment may need
to be repeated every few years. Hence, the
FDA’s terminology that CK was FDA approved
“for the temporary” reduction of
hyperopia
and/or presbyopia. It does not state that
the treatment has a permanent effect,
however, for an individual with +2.5
diopters of hyperopia, it might be eight or
ten years or more before the effect has
completely regressed. Nonetheless,
re-treatments will be a necessity for most
individuals to maintain the full effect of
the original treatment.
Clinical Studies Regarding the ViewPointä
CK System for Hyperopia
In the U.S. clinical studies of the
ViewPointä CK System, patients age 40 and
above with 0.75 to 3.25 diopters of
hyperopia were treated. Nine months after
the procedure 50% of the patients had 20/20
uncorrected vision, 74% had 20/25 or better
uncorrected vision, and 93% had 20/40 or
better uncorrected vision[viii].
There were no statistically significant
differences in contrast sensitivity testing
between pre-op and post-op eyes. This
indicates that patients have good quality
vision, that is, it is sharp and there is no
degradation of night vision.
Patients in the U.S. clinical studies that
supported FDA approval for treatment of
hyperopia were required to complete a
questionnaire regarding their satisfaction
with their results. Approximately 80% of
the patients surveyed were “satisfied” or
“very satisfied” with their CK results. Six
percent of the patients reported being
“dissatisfied” with the results and 3% were
“very dissatisfied” with their CK results.
Ioannis G. Pallikaris, M.D., Ph.D., the
esteemed and highly respected refractive
surgeon at the University of Crete, Greece,
completed one of the longest-term studies on
CK for
hyperopia[ix].
In his study, 38 eyes of 26 patients were
treated for hyperopia with the Refractec
ViewPointä CK System and followed for 30
months. At 30 months post-op, uncorrected
visual acuity was 20/20 or better in 52.5%
and 20/40 or better in 89% of eyes. No eye
lost more than one line of Snellen eye chart
visual acuity or had induced
astigmatism of
greater than 2.0 diopters. Again, in their
study, there were no statistically
significant changes in contrast sensitivity
between pre-op and post-op eyes.
In another study conducted at Stanford
University Department of Ophthalmology,
Danny Y. Lin, M.D. and Edward E. Manche,
M.D. completed CK on 25 eyes of 14 patients
and followed-up for two years. They found,
two years post-operatively, the uncorrected
visual acuity was 20/20 or better in 64% of
eyes and 20/40 or better in 95% of eyes. No
eye lost more than one line of best
spectacle corrected visual acuity or had
induced astigmatism greater than 0.75
diopters. They found the rate of regression
of effect was only +0.024 diopters per month
between 12 and 24 months. This is only
+0.29 diopters of regression in that year,
which is consistent with previous results.
Clinical Studies Regarding the Use of CK
for Presbyopia
In the clinical studies conducted to
evaluate the safety and effectiveness of CK
for the treatment of resbyopia, a total of
150 patients (188 eyes) were enrolled and
underwent treatment at five different
centers[x]..
This study was part of the Phase III
multicenter clinical trial of Refractec’s
ViewPointä CK System for the treatment of
presbyopia. One hundred twelve patients
underwent CK in their non-dominant eye
only. The remaining 38 patients had CK in
both eyes because their dominant eye was
hyperopic (farsighted). The average patient
age was 53 years.
At the one-year post-op interval, 89% of the
eyes treated for near could read newspaper
size print or smaller. Interestingly,
distance vision remained very good with 97%
having uncorrected visual acuity at distance
of 20/20 or better and 100% had 20/40 or
better.
With regard to safety, the data was
exceptional. Two of the eyes in the group
had a transient decrease in vision of more
than two lines of best spectacle corrected
visual acuity at the one-month post-op time
interval. However, this vision degradation
had resolved in both eyes by three months.
Contrast sensitivity testing in dim light
(sopic contrast sensitivity) was unchanged
from pre-op to post-op. There was not a
single device related adverse event.
Subjectively, 98% of patients stated
their vision was “improved”.
Eighty-four percent were “satisfied” or
“very satisfied”. The quality of depth
perception was rated as “fair” to
“excellent” by 100% of patients.
GeGeneral Risks and Complications With CK
Risks associated with CK are under 1%,
however, as with any procedure, a good
candidate is properly informed. In October,
2004, I did an interview with Marguerite
McDonald, M.D., who was a medical monitor
and clinical investigator for the FDA
clinical trials involving CK. When I asked
her about the safety of CK, including any
post-op visual aberrations, she replied, “In
recent studies, CK has been shown to
decrease higher aberrations. Actually it was
the safest {ophthalmic} device ever to be
presented to the American FDA. The incidence
of complications and adverse events was
lower than anything they had ever seen. They
have very strict criteria and they {the FDA}
only approve very safe devices or procedures
and this was still the safest device ever
presented for those with hyperopia”.
Some patients will present with blurred
vision, especially the first few days after
surgery. This is expected. A very small
percentage of patients will have any
significant induced
astigmatism when “Light
Touch CK” is utilized. However, when this
minor complication occurs, the surgeon can
often just place a “bonus spot” that will
help alleviate the astigmatism. As reported
at MyClearVision.com, the official website
for fractec, Inc., the following side
effects may rarely occur with CK[xii]:
· Discomfort and/or foreign body
sensation
· Glare
· Halos
· Overcorrection
· Tearing
In the FDA controlled clinical trials, only
1% of patients had loss of two or more lines
of best spectacle corrected visual acuity
(BSCVA) on the Snellen eye chart
postoperatively. In other words, if a
patient had 20/20 vision pre-operatively and
the BSCVA postoperatively was 20/30, this
represents loss of two lines of vision on
the eye chart. None of the post-op eyes in
the FDA trials had a BSCVA worse than 20/40,
which is the level of vision required to
pass a driver’s license exam in most
states. Also, no eyes that had 20/20 or
better vision pre-op had any worse than
20/25 BSCVA one year post-operatively.
Importantly, and this bears repeating in
reference to safety, there were no
statistically significant differences in
contrast sensitivity testing in pre-op
versus post-op eyes. Only 1% of eyes
had significant induced astigmatism. One
percent of patients complained of double
vision (usually due to
astigmatism) and 1%
of patients also had an increase in
intraocular pressure (pressure inside the
eye greater than 25 mm Hg). The increase in
intraocular pressure is probably unrelated
to the procedure itself, however, as this
may occur naturally, especially in the group
represented here (age greater than 40)[xiii].
It should be mentioned that, although there
are no long-term studies with CK patients,
there is at least two and one-half years of
follow-up on the early adopters of the
procedure. In these patients, CK has been
shown to be safe, effective, and predictable
for correcting low to moderate degrees of
hyperopia and presbyopia.
When Should CK Not Be Used?
Taken directly from the FDA’s “New Device
Approval”, effective April, 17, 2002,
conductive keratoplasty (CK) should not be
used for patients who[xiv]:
· are pregnant or nursing
· have an abnormally shaped cornea
· have thinning of the cornea
· have a history of herpes infection in the
eye
· have an untreatable dry eye
· have an autoimmune disease (e.g., systemic
lupus)
· have a collagen vascular disease (e.g.,
rheumatic fever)
· have clinically significant allergies
· are insulin dependent diabetics
· have a compromised immune status (lack of
ability to fight diseases)
· have an implantable electrical device such
as a pacemaker, defibrillator, or cochlear
implantConclusions Regarding CK with
ViewPoint CK System
The evidence appears conclusive to me that
conductive keratoplasty with the Refractec
ViewPointä CK System is safe, effective, and
predictable for those with mild to moderate
hyperopia up to +3.25 diopters. Remember,
CK is only FDA approved for individuals age
40 and above!
Using CK in individuals younger than age 40
may occasionally be suitable, and this is
perfectly legitimate and legal. When a
physician uses a device or procedure in a
manner that is not exactly consistent with
FDA approval, this is known as “off-label
use”. Off-label use is common and
acceptable. In many cases, it simply means
that the FDA trials did not look at the
device, procedure, or medicine for that
particular indication or subset of
patients. If you are 38 or 39 years old,
have
hyperopia up to 3.25 diopters, and you
desire CK, just discuss this with your
refractive surgeon. You might be a
candidate.
In general, however, if you have hyperopia
of +1.0 to about +3.75 diopters and you are
under age 40, you should probably only be
considering LASIK, Epi-LASIK, or
IntraLASIK
as potential surgical solutions to your
refractive error. If you are under age 40
and you are +4.0 diopters hyperopic or
above, in general, I do not recommend any
type of surgery. The risks would generally
outweigh the benefits. If you are over age
40 and are +4.0 diopters or above, then you
should consider
refractive lens exchange
(RLE), which is detailed in Chapter
Thirteen. Please refer to the refractive
surgery nomogram for more on these
recommendations (Chapter Six).
For those who are fortunate enough not to
require any glasses or contact lens
correction for distance, but who are
troubled by the need for readers and are age
40 and above, CK is an excellent option.
Treatment with CK for presbyopia showed
outstanding results with an extraordinary
degree of safety. Plus, the efficacy and
predictability is there, even in the FDA
controlled trials. As eye surgeons have
gained further experience post FDA approval,
developments such as “Light Touch” CK have
allowed treatment with even fewer RF spots
and perhaps even better visual outcomes.
If it were my eye, I would choose CK over
any other procedure if I were hyperopic (up
to 3.25 diopters) and over age 40. If I
were presbyopic and required reading glasses
(I am presbyopic but I am myopic in my
non-dominant eye after LASIK in 1996), I
would choose CK for my non-dominant eye. In
this
website, CK gets an “A” as a refractive procedure for the hyperopic and presbyopic…
and I don’t grade on the curve!
[i] Vinciguerra P, Kohnen T,
Azzolini M, Radice P, Epstein D,
Koch DD. Radial and staggered
treatment patterns to correct
hyperopia using noncontact holmium:
YAG laser thermal keratoplasty. J
Cataract Refract Surg.
1998:24(1):21-30.
[ii] Tassignon MJ, Trau R,
Mathys B. Treatment of hypermetropia
with the holmium: YAG laser – laser
thermokeratoplasty (LTK) {in
French}. Bull Soc Belge Ophthalmol.
1997;266:75-83.
[iv] Lindstrom, RL,
Durrie, DS, Wu, HK. Perspectives
on Conductive Keratoplasty, Royal
Hawaiian Eye Meeting 2005 Symposium,
Monographs – Ocular Surgery News. July
15, 2005.
[v] Lindstrom, RL, Durrie, DS, Wu,
HK. Perspectives on Conductive
Keratoplasty, Royal Hawaiian Eye Meeting
2005 Symposium, Monographs – Ocular
Surgery News. July 15, 2005.
[vi]] Light-touch technique offers
potential for CK improvement. Ocular
Surgery News. July 1, 2005 issue.
[vii] Personal Interview of
Marguerite McDonald, M.D., by
Chris
A. Knobbe, M.D., published via the
Web at EyeMDLink.com, Nov, 2004.
Available at:
http://www.eyemdlink.com/NewsArticle.asp?NewsID=42
[viii] Refractec Patient Information
Booklet. Copyright 2001.
Available at:
www.fda.gov/ohrms/dockets/ac/01/briefing/3806b1_03_PatientBooklet_draft.PDF
- 11-29-2001.
[ix] Ionnis G. Pallikaris, MD, PhD,
Tatiana L. Naoumidi, MD, Nikolaos I.
Astyrakakakis, OD. Long-term results of
conductive keratoplasty for low to
moderate
hyperopia. Journal of Cataract
and Refractive Surg. Vol. 31, Issue 8,
pp. 1520-1529 (August 2005).
[x] McDonald, MB, Durrie DS, Asbell,
PA, Maloney R, Nichamin L. Treatment of
presbyopia with conductive keratoplasty:
six-month results of the 1-year United
States FDA clinical trial. Cornea.
2004;23:661-668.
[xiii] Refractec Patient Information
Booklet. Copyright 2001.
Available at:
www.fda.gov/ohrms/dockets/ac/01/briefing/3806b1_03_PatientBooklet_draft.PDF
- 11-29-2001.
[xiv] New Device Approval, FDA
website, ViewPoint CK System.
Available at:
www.fda.gov/cdrh/mda/docs/p010018.html -
Posted: 04-17-2002.
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