Success with conductive keratoplasty includes careful centering, inking

The loose lens test is a helpful way to interact with patients, find good candidates and determine realistic surgical expectations.

WAILEA, Hawaii — Centering carefully and marking the cornea with a marker that has been inked several times when performing conductive keratoplasty may improve postoperative visual results.

“I center over the center of the entrance pupil and repeat it under two levels of illumination: dim and bright,” said Marguerite B. McDonald, MD, FACS, director of the Southern Vision Institute and clinical professor of ophthalmology at Tulane University. She spoke here on conductive keratoplasty (CK) at Hawaii 2003: the Royal Hawaiian Eye Meeting.

Dr. McDonald uses a halogen otoscope as a coaxial illumination source, along with a Sinskey hook to make the epithelial mark. She said to press firmly when marking the cornea.

“Press for several seconds, but remove the marker very quickly to avoid a smeared mark, which makes surgery much more difficult,” she said.

For enhancement, Dr. McDonald recommends marking the position of the old spots before taking the patient into surgery.

“The marks often disappear under the operating microscope,” she said.

She marks the old spots at the slit lamp, using a speculum and an inked Sinskey hook or fine-tipped marking pen.

“You want to avoid these areas for enhancement,” she said.

A good operating microscope is necessary to observe the impressions of the marker on the epithelium.

“The ink can be misleading if it smears. The indentation is the most accurate way to locate the proper position of the treatment spots,” said Dr. McDonald, a principal investigator for the presbyopia clinical trial of CK. “If all else fails, abort the case and let at least 30 minutes pass. That way, the smeared marks will have faded and you can try again.”

Astigmatism

Once the initial treatment plan is executed, patients should be checked with both a keratometer and the Mastel ring to locate the amount and axis of the astigmatism.

“I use the keratometer to determine exactly how much cylinder is present, and the Mastel ring to precisely locate it,” Dr. McDonald said.

If the intraoperative Ks indicate more than 2 D of astigmatism, an extra spot is added on the 7-mm ring in the flattest meridian.

“But to create this extra spot, there must be more than 2 D of astigmatism on keratometry,” she said.

If an extra spot is created, Dr. McDonald checks again and continues to add additional spots until the cylinder is 2 D or less.

“Higher corrections — with more treatment spots — are more likely to induce cylinder. However, the need for extra spots, especially more than one, decreases with surgeon experience,” she said.

To successfully incorporate CK into a refractive practice, physicians and their staff need to have a new vocabulary, and everybody has to be consistent, Dr. McDonald said.

“We have pretty much banished the word monovision; instead, we use the phrase ‘blended vision,’” she said.

Practices must also ensure that they project an image of credibility, without overpromising.

“Emphasize the value of the procedure to the person and not the technology,” Dr. McDonald said. Physician confidence in performing CK is important as well.

Lens test

“The loose lens test is a wonderful way to interact with the patient, find good candidates and manage expectations,” Dr. McDonald said. “Lenses need to be loose because you’re going to be flipping them up very quickly, and you’re going to be handing them to patients.”

The four recommended powers are +0.75 D, +1.5 D, +2 D and +2.5 D.

“I have always had a rule in my practice that I’ve never broken until now, which is don’t mention refractive surgery to happy people who don’t mention it first. If they’re wearing glasses or contacts, don’t even mention LASIK. Don’t mess with success. But I’ve learned that low hyperopes and plano presbyopes are ‘secret shoppers.’ They want you to initiate the dialogue about CK,” Dr. McDonald said.

Results of the loose lens test tend to underestimate the results of actual CK, but patients who are happy with the test will nearly always be satisfied postoperatively, she said.

“Patients just love the interactive aspect. They get to know you, and you get to know them very quickly. It’s an excellent way to communicate the advantages and limitations of vision correction with CK,” she said.

A contact lens trial can also be offered as a supplement to a loose lens test, though this is rarely necessary.

Reinforcing expectations

After surgery, patients need to be encouraged, and they should also be reminded of the need to wear reading glasses on occasion.

“Keep reinforcing the goal of vision for daily life, such as being able to read the instructions on a microwave dinner, a price tag at the clothing store, restaurant menus and engage in light reading. If you are involved in a detailed activity, like taking a sliver out of your grandson’s palm, you’ll need reading glasses. But for most of your life you’ll be free of glasses,” Dr. McDonald said.

In patients over 40 years old with up to 2.5 D of hyperopia, Dr. McDonald no longer performs LASIK.

“I also will do CK between 2.5 D and 3 D, though the enhancement rate is higher,” she said.

“I just do CK,” she said. “That’s how confident I am about the procedure.”

Failed monovision contact-lens wearers, pseudophakes, post-photorefractive keratectomy patients and radial keratotomy patients up to eight radials may also be considered, though the surgical approach to these patients is still under study.

Clinical results for CK for presbyopia promising NEW ORLEANS — The most recent data from the Food and Drug administration phase 3 clinical trial of conductive keratoplasty for the treatment of presbyopia are promising, according to Marguerite B. McDonald, MD, FACS. The 12-month follow-up of 130 patients (160 eyes total) found that 97% of patients could see 20/20 in the distance and read magazine- and newspaper-size print. Three-fourths of patients could see 20/20 and read J2 on an eye chart. Overall, 96% of patients reported being “satisfied” to “very satisfied” with their outcome. CK creates a band of collagen shrinkage that steepens the central cornea to reduce hyperopia. (Artwork courtesy of Refractec.) The majority of study patients were plano or emmetropes. “I really expected excellent results and we are achieving them,” Dr. McDonald said. Enrollment of about 200 patients has been completed. “It is a landmark, of course, that we have finished enrollment. We can close the door now and just track these people,” she said. Officials at Refractec Inc. said they anticipate filing for FDA premarket approval later this year, with approval expected in early 2004. Between April 2002 and January 2003, nearly 7,000 procedures were performed nationwide. The appeal of an outpatient office procedure has been established in demographic studies, Dr. McDonald said. “CK opens the door for refractive surgeons to interact with a completely different group from our LASIK population. Patients tend to be 10 to 15 years older than the average LASIK patient. They are also risk-adverse. They like the idea that there are no blades involved with CK,” she said. Topical anesthesia is applied and the procedure take less than 5 minutes. For the most part, CK also circumvents the dry-eye issue that is prevalent in older patients who undergo LASIK. “The CK treatment spots are so tiny, they interrupt very few corneal nerves,” Dr. McDonald said. Furthermore, refractive change closely mirrored the slow hyperopic creep in natural hyperopes who never have surgery.

For Your Information:

• Marguerite B. McDonald, MD, president of the American Society of Cataract and Refractive Surgeons, can be reached at the Southern Vision Institute, 2820 Napoleon Ave., Suite 750, New Orleans, LA 70115; (504) 896-1240; fax: (504) 896-1251; e-mail: margueritemcdmd@aol.com. Dr. McDonald is a paid consultant for Refractec.

• Refractec Inc., manufacturers of the ViewPoint CK system, can be reached at 5 Jenner, Suite 150, Irvine, CA 92618; (949) 784-2600; fax: (949) 784-2601.