New Energy for Your Practice?
A look at how CK can expand your refractive offerings.
By Stephen Pascucci, M.D.

Now that conductive keratoplasty (CK) has received FDA approval for correction of low-to-moderate hyperopia, interest in this procedure is growing rapidly. With that in mind, we asked nine surgeons who've performed this surgery to share some of what they've learned. Hopefully, their experiences will answer questions you may have about the procedure and shorten the learning curve if you choose to add CK to the options you offer your hyperopic patients.

To start, we asked Stephen Pascucci, M.D., to talk about:

• how the procedure works
• what kind of results you and your patients can expect
• how CK compares to other hyperopic procedures
• why hyperopic patients tend to prefer it to the alternatives
• how he fits it into his practice on a day-to-day basis.

Then, we asked eight other surgeons to share pearls from their experience performing the surgery and working with CK patients, both pre- and post-op.

• Some hyperopic procedures, such as hexagonal keratotomy, were modifications of myopic procedures and only moderately successful at best.
• Procedures such as clear lens extraction and replacement with IOLs have been successful, but many surgeons are reluctant to resort to such invasive procedures when performing elective surgery for low refractive errors.
• For a while it appeared that holmium YAG laser thermo-keratoplasty (LTK) would fill the need for a specific procedure for the correction of hyperopia. However, because of significant over-corrections, loss of uncorrected distance vision and regression over time, LTK hasn't met the expectations of most patients and surgeons.
• Of all the existing options, LASIK for hyperopia has been the most successful and effective procedure: It's produced minimal over-corrections, stable outcomes and low regression rates. Unfortunately, the irreversible nature of LASIK and the steps involved in the procedure don't appeal to the conservative hyperopic population. This probably explains why hyperopic LASIK typically comprises only about 15% of a surgeon's laser vision correction practice.

One of the biggest advantages offered by CK is that it avoids many of the problems that have undercut the success of the other procedures.

How CK works

Conductive keratoplasty is a form of thermokeratoplasty, performed using the CK ViewPoint System that's manufactured by Refractec Inc., in Irvine, Calif. FDA guidelines for the procedure state that patients should have between +0.75 and +3.25 diopters of hyperopia and no more than 0.75 diopters of cylinder.

To perform CK, the surgeon inserts a probe, 450 microns long and about 90% as wide as a human hair, into a series of spots forming a circular band around the mid-periphery of the patient's cornea. The probe releases controlled high-frequency radio wave energy (350 kHz), and the impedance, or electrical resistance, of the corneal collagen causes it to heat up in response. The heating causes the collagen to shrink in a predictable manner. The resulting shrinkage produces an effect akin to tightening a belt around the periphery of the cornea, causing the central cornea to steepen.

Typically, the procedure is performed on an outpatient basis in a short-procedure-room setting, using an operating microscope and topical anesthesia. A standard procedure takes 3 to 5 minutes.

How well does it work?

So far, the data indicate that CK is effective and stable over time. Researchers believe that the reason CK works so well is that the effects of the treatment penetrate more than 500 microns into the cornea. This makes it possible to achieve a stable hyperopic treatment without cutting or removing corneal tissue.

Some statistical data:

• In trials, the CK procedure met or exceeded FDA safety requirements. Less than 1% of patients lost more than 2 lines of best-corrected vision at 6 and 9 months, and that number dropped to zero at 12 and 24 months.
• All patients had a best-corrected visual acuity of at least 20/40 at every point during follow-up. Nearly 90% of patients achieved 20/30 vision or better by 12 months after CK.
• Regression has been minimal: The mean loss of correction over 12 to 24 months was 0.28 diopters.
• Induced astigmatism appears to be the most undesirable side-effect following CK, but it occurs infrequently. Only 2 to 3% of patients had an increase in astigmatism of more than 2D at the 1- and 3-month visits. This declined to less than 1% by 9 to 12 months and was 0% by 24 months. Also, any induced cylinder appears to be regular and does not, typically, influence best-corrected visual acuity. (Note: CK produces slightly more induced astigmatism than LTK. However, patients experience more regression of the hyperopic correction after LTK.)

The FDA is currently requiring label wording stressing that CK produces "a temporary reduction of hyperopia," because of the limited amount of follow-up data available when CK was approved. If future data continue to show stability of the correction, this requirement could eventually be dropped.

Meeting patients' needs

Traditionally, hyperopic patients are older than myopic patients. They're also more conservative and risk-averse. When I conducted an informal survey of patients 40 to 60 years old who were considering vision correction surgery and asked what factors were most important to them when choosing which procedure to undergo, the two factors ranked the highest were:

• the safety of the procedure
• not cutting the cornea.

Other surgeons have told me that their middle-aged patients say the same thing. That might explain why, out of 60 million hyperopic patients in the United States, few have seriously considered LASIK, let alone had the procedure.

To gain acceptance in hyperopic circles, CK must not only meet the safety yardstick but must specifically address the visual concerns and frustrations of this group of patients. Typically, these patients have had good vision all their lives; now that their vision has begun to deteriorate with age, they're very frustrated. They want to regain near visual function but at the same time not sacrifice distance vision. Regaining near and intermediate function -- without losing distance acuity -- allows an aging hyperopic patient to feel younger and healthier again.

The desire to retain distance vision is part of the reason that LTK hasn't fared too well with these patients. The LTK procedure often overshoots the desired refractive result, with an attendant loss of distance vision. This is perceived as a significant drawback by these patients.

Because CK promises to do a good job of giving these patients what they want, I believe the hyperopic population will embrace CK in a way they haven't embraced previous options. This should result in a more equal balance between the number of myopic and hyperopic refractive correction procedures performed every year.

How we use it in our practice

Currently, my CK population represents about 15% of our vision correction procedural volume -- about the same as our percentage of LASIK. (We offer all refractive services, except phakic IOLs.) I expect this percentage to increase as the public learns about CK and its advantages compared to LASIK.

We set aside a specific time during the week to see patients who are interested in an evaluation for vision correction procedures. Our evaluation for CK typically takes 2 hours; it's similar to our evaluation for laser vision correction procedures.

If all is well, we make sure the patient is thoroughly educated about the procedure, including the temporary decrease in distance vision and symptoms that may be experienced in the immediate post-op period. I ask the patient to take home our informed consent document, read it carefully, and sign it if he's in agreement. (For a discussion of the informed consent document, see "Getting Informed Consent".)

Questions frequently asked by potential patients include:

• What are the differences between LASIK and CK?
• What do I (the doctor) recommend?
• What will happen immediately post-op? Will it interfere with my ability to return to work and daily life? (I tell them they'll most likely be able to drive within 1 to 2 days.)

Among those patients who investigate the possibility of having CK done, the acceptance rate is high.

To make sure things go smoothly during the procedure:

• We perform the procedure in our ASC.
• I schedule CK on the same days that we perform laser vision correction procedures. We group the patients by procedure.
• During the procedure, I use the microscope of our excimer laser, although you could use a short-procedure room and a coaxial microscope for the same purpose.

	The ViewPoint CK System from Refractec Inc.

CK doesn't require any special instrumentation (other than the ViewPoint System used to perform the procedure) or a special recovery room. So far, we've purchased one ViewPoint unit; it's about the size of a VCR, which makes it easy to move from location to location. In general, the costs per case run lower than the cost of performing LASIK, so I don't expect it to take a long time to recoup our investment.

For now, we're marketing the procedure via seminars and print ads, but we intend to begin a radio and TV ad campaign soon.

Outlook: promising

Success in the marketplace depends, in part, on how the company behind a procedure handles its introduction. Refractec has been very careful to introduce CK into the market in such a way that the initial cases are being handled by experienced refractive surgeons who can, in turn, introduce the procedure to others.

CK also holds promise as a treatment for several refractive problems that previously weren't considered severe enough to warrant riskier procedures. Researchers in other countries are considering using CK to treat presbyopia, progressive hyperopia following RK, astigmatism, hyperopic surprises following IOL procedures, undercorrected LASIK-H, over-corrected myopic LASIK and refractive cylinder in Keratoconus.

In the meantime, our initial patients are quite happy with their results. With good outcomes and multiple potential uses, it seems likely that CK will further fuel the public's interest in vision correction procedures. That bodes well for both hyperopes and their doctors.

Dr. Pascucci practices at Northeastern Eye Institute in Scranton, Pa. His practice focus includes refractive surgery as well as cornea, external disease and anterior segment surgery.

Conductive Keratoplasty in Practice: Helpful Strategies

We asked eight surgeons who perform CK to share "pearls" from their experience. For convenience, we've organized their comments into sections covering:

• patient selection
• preparing the patient
• marking the cornea
• performing the operation
• treating astigmatism
• post-op care.

Patient selection

As with any procedure, selecting appropriate patients is key:

Edward E. Manche, M.D.: Choose your CK patients carefully. Ideal patients for conductive keratoplasty are in their late 40s or early 50s with low hyperopia (about 1.5 diopters) and little or no astigmatism.

These patients have had excellent distance vision all their lives and they're bothered by the need for glasses for near and intermediate vision. They tend to be risk adverse, and they like the safety profile of CK.

Penny A. Asbell, M.D.: Good candidates for CK include:

• patients in their 40s who say they have great distance vision without glasses, but complain that reading is becoming difficult
• patients in their 50s who say they have great distance vision without glasses, but need reading glasses for near
• hyperopic patients in their 50s who wear bifocals or progressives.

If the patient's current refraction is about +1D, CK will help the patient maintain good distance vision and provide good near vision without the need for glasses. However, if the refraction is between +1 and +3D, results will depend on the patient's age. Older patients will still need reading glasses post-surgery.

Note: Occasionally, an autorefractor will show low minus power when the patient is really a hyperope. You can check using manual refraction.

Robert K. Maloney, M.D.: CK needs to be properly positioned in the practice. It's appealing to the risk-averse baby boomer as a safe alternative that doesn't cut the eye or remove tissue. We position it as the safest method for correcting low and moderate levels of hyperopia, and this attracts patients who wouldn't come to see me for LASIK.

Preparing the patient

It's crucial to make sure that patients have realistic expectations about post-op visual changes:

Edward E. Manche, M.D.: It's important to counsel patients preoperatively about what to expect in the post-operative period. They should expect an immediate improvement of near vision with some blur at distance, the result of transient consecutive myopia and induced astigmatism. The transient myopia will resolve within 2 to 6 weeks, and any induced astigmatism should resolve over the first 3 to 6 months.

Dan Durrie, M.D.: Patients have a tendency to continue to improve over the first week after the procedure, so I make sure to tell them that. I tell them to expect 25% improvement in the first few hours, 50% over the next couple of days, and that by the end of the week their reading and distance vision should be significantly improved.

Penny A. Asbell, M.D.: Remind patients that CK won't prevent aging-related changes inside the eye -- we all develop an increasing need for reading glasses as we age.

Marking the cornea

To ensure accurate placement of the corneal marks:

Dan Durrie, M.D.: Make sure the ink on the marker is very dry. Also, don't use too much ink, or it may smudge. Placing your marks in the appropriate spots on the cornea is the most important part of the procedure.

Marguerite McDonald, M.D.: When you make the inked mark on the cornea, press down slowly and firmly, but release pressure very quickly and get the marker away from the cornea. This is because the cornea "bounces back" several times a second after the pressure is released, causing multiple marks to be made. If you end up with multiple marks, it will be so difficult to follow the pattern that you might have to cancel the case.

It's also helpful to tell the patient not to move at the exact moment that you're marking the cornea.

Peter S. Hersh, M.D., F.A.C.S.: Make sure you dry the surface of the cornea so that your markings stay put, and to avoid creating a well of water around the probe. Water will decrease energy uptake, increasing the risk of inducing astigmatism.

Jonathan M. Davidorf, M.D.: Three useful strategies:

• While you're still working out your nomograms, we recommend being conservative -- it's easy to add additional spots to fine-tune outcomes, so you should err on the side of undercorrecting.
• Avoid placing spots inside the 6-mm zone; there's a point beyond which you'll cause corneal flattening rather than steepening. That's why centration is so important.
• Make sure the patient is fixating coaxially while you mark the center of the pupil. As with other refractive procedures, the debate still looms about whether or not line-of-sight centration would be preferable. For now, we do know that center-of-pupil centration works well, and we're evaluating the comparative merits of line-of-sight centration.

R. Bruce Grene, M.D.: CK is a straightforward procedure, but, as is true of all refractive surgery, it requires intense attention to detail. Be sure you center the marking ring and use uniform application technique for each probe spot.

Performing the operation

Once the cornea is correctly marked:

Jonathan M. Davidorf, M.D.: Make sure that hydration is uniform -- but don't overdo hydrating the eye. I prefer to apply the probe on a uniformly dry cornea, taking care to avoid causing desiccation and disruption of the corneal epithelium. The energy used during CK conducts through the fluid on the cornea, so the amount of moisture present will affect how much shrinkage occurs at each spot. If one area is more moist than another, you may induce astigmatism.

Peter S. Hersh, M.D., F.A.C.S.: Two useful strategies:

• Be pretty vigorous with your initial push into the cornea; then wait a few seconds before giving the application. You'll initially get a little "pop" through Bowman's membrane, and then the cornea will lift up a little and engulf the probe. By waiting a few seconds you allow the probe to become well-seated. It also helps you to make sure you're at the proper depth, which is another way to avoid inducing astigmatism.
• When I'm treating with more than one concentric ring, I like to start my treatments at the 7-mm ring before proceeding to the 6-mm ring, rather than starting with the 6 and proceeding to the 7. This allows me to meticulously place the 6-mm ring to get perfect centration.

You can also use those first two 7-mm spots as your guide, and if you find that you're off a little bit, you can make up for that in your 6-mm spots.

Marguerite McDonald, M.D.: Check the tip for charred epithelial debris between treatment spots. Crusted epithelium can prevent the tip from being fully seated.

Dan Durrie, M.D.: I use a Mastel fixation device, which provides great illumination and also gives a qualitative keratometry reading to let me know whether I've induced any astigmatism with the procedure.

Treating astigmatism

CK can also be a powerful tool for correcting astigmatism:

Jonathan M. Davidorf, M.D.: We've corrected as much as 3D of astigmatism using CK; in Mexico they've treated more than 6D of astigmatism.

To correct mild astigmatism, you can start by moving spots along the steep meridian out slightly. If your nomagram calls for 16 spots, for example, you can pull 2 spots along the steep meridian from 6 and 7 mm to 7 and 8 mm.

An alternative way to treat astigmatism is to place additional spots along the flat meridian. But be careful: This is a powerful tool. I don't recommend placing spots closer than 8 mm for the purpose of treating astigmatism. I prefer to place the extra spots at the 8 or 9 mm zone.

Post-op care

To help patients manage post-op discomfort:

Jonathan M. Davidorf, M.D.: Our typical CK patients report post-op tearing and mild grittiness, rather than pain. NSAIDs do seem to help make them more comfortable. We're still not sure whether a post-op bandage contact lens makes a significant difference in comfort. (Currently, I'm not using bandage contact lenses.)

R. Bruce Grene, M.D.: In our experience, CK patients have 2 to 3 days of moderate discomfort. We treat them with a shorter version of the regimen we developed for PRK post-op care:

• Ocuflox (Allergan) tid for 3 days
• Pred Forte (Allergan) tid for 3 days
• Acular unit dose (Allergan) tid for 3 days
• Celluvisc (Allergan) prn for irritation
• tetracaine unpreserved qd for pain not relieved by Acular and Celluvisc.

Robert K. Maloney, M.D.: CK patients are somewhat less comfortable than LASIK patients in the first 24 hours postoperatively. To ensure the patient's comfort, I use a bandage contact lens and give the patient about 30 drops of sterile tetracaine to use as needed during the first 24 hours.