Conductive Keratoplasty For Presbyopia & Hyperopia

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 ViewPoint 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.

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

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 implant

Conclusions 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!
 

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[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.

[iii] Food and Drug Administration. ViwPoint CK System – P010018. Rockville, MD: Dept of Health and Human Services; April 11, 2002. Available at http://www.fda.gov/cdrh/pdf/P010018a.pdf. 

[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.

[xi] 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

[xii] Reported side effects, My Clear Vision.com website, available at: http://www.myclearvision.com/410.asp?nav=400

[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.