Light-touch technique offers potential for CK improvement

The 1-mm compression technique is still in early stages of use but has proven to cause less induced cylinder than conventional CK.

CLEVELAND — A new approach to conductive keratoplasty, NearVision CK with LightTouch, has certain advantages over the conventional method, Marguerite B. McDonald, MD, FACS, reported here.

At The Cleveland Clinic Foundation Cornea and Refractive Surgery Summit 2005, Dr. McDonald discussed the current findings on this minimal-compression technique, which has been in use only since April 2004.

Marguerite B. McDonald, MD, FACS

The technique is a modification of the key factors that influence the effectiveness of CK: the number of spots, the diameter of the spot placement and the amount of pressure used by the surgeon. Initially described by H.L. Rick Milne III, MD, it involves making a 0.5 to 1 mm compression of the cornea with the keratoplasty tip during application of the radiofrequency energy. The dimple produced with CK with light touch is one-fifth to one-seventh the size of the corneal dimple produced in the conventional method, according to Dr. McDonald. Additionally, approximately 80% of patients need only eight treatment spots with CK with light touch vs. most needing 16- or 24-spot treatments with conventional CK.

“The inspiration came from a patient who had a shallow anterior chamber, and I did not want to compress his cornea,” Dr. Milne said in a follow-up interview with Ocular Surgery News. “At 1 week postop, he had a remarkably greater response compared to my patients that received conventional CK.”

Dr. Milne said that he immediately knew what he had done to cause the difference and decided to treat additional patients with the CK light-touch technique, thereby achieving similar results.

The difference

With conventional CK, the keratoplasty tip depresses the cornea and the foot pedal is pushed at the moment of maximal pressure, creating a dimple in the cornea and a light ring around the keratoplasty tip from 5 to 7 mm, Dr. McDonald explained. With CK with light touch, the surgeon barely touches the cornea, she said.

“It’s easier to apply identical amounts of light pressure on the cornea than to produce identical amounts of extreme pressure on the cornea. In other words, with the conventional technique, there are certain positions with your hand where you’re probably not pressing as hard as others,” she said. “By just touching the cornea lightly when applying all CK treatment spots, which are now placed further from the visual axis, there’s less induced astigmatism.”

“Another advantage is that fewer treatment spots are needed to get a clinically significant effect, so when the patient returns in a couple of years [for a vision upgrade] there’s more space for additional touch-ups,” she added.

Dr. Milne said he believes the variability of compression between each spot is the key to cylinder.

Dr. McDonald advised instructing the patient to look at the fixation light during CK with light touch because otherwise the patient is able look away, whereas with conventional CK the patient is unable to move due to the pressure.

Dr. Milne’s technique is slightly different.

“I have the patients look at the fixation light only initially to get their eye into the right position, but then have them pretend to hold their eye still like they are a statue,” he said. “If they are trying to fixate on the light while the probe is being seated, then they will move their eye, because whenever the surgeon touches the cornea it makes the fixation light appear to move.”

Dr. McDonald emphasized that a steady hand position is important.

Although there is currently no proven nomogram for CK with light touch, some physicians who have been practicing the technique have been using Dr. Milne’s nomogram, according to Dr. McDonald.

Dr. Milne and Daniel S. Durrie, MD, pooled their data on light-touch CK to compare its efficacy to that of conventional CK (Figure). When comparing this limited data on CK with light touch to the Food and Drug Administration’s clinical trials data on conventional CK, the light-touch outcomes are better and are achieved with fewer spots, Dr. McDonald said.

In a side-to-side comparison of the pooled data with the CK FDA presbyopia clinical trials, she explained, the outcomes from CK with light touch are better than the conventional method in several ways, including the percentage that are within ±0.5 D of the intended outcome (85% vs. 63%); the percentage with no change in cylinder (90% vs. 71%); the percentage with less than 1 D of induced cylinder (6% vs. 17%); and the percentage with greater than 1 D of induced cylinder (4% vs. 12%).

Side-by-side comparison: Conventional CK vs. light-touch CK. Images: Refractec

Advantages

Light-touch CK provides a more robust effect, less postoperative discomfort because of fewer spots, less induced cylinder and better uncorrected near vision in a shorter time postoperatively, Dr. McDonald said. She said that it is not completely clear why better uncorrected near vision occurs sooner – perhaps because there is less corneal edema when spots are fewer and are applied further from the visual axis – but “patients are happier and therefore surgeons and staff are happier” as a result.

Another way to ensure patient satisfaction with both conventional CK and CK with light touch is to target the right patient population, she emphasized.

“You have to become personally involved in the process and interact with the patient to make sure the patient’s expectations are set correctly,” she advised.

Reflecting on her experiences with conventional CK patients, Dr. McDonald said people need to be informed that they will most likely need a touch-up in 2 years as their presbyopia progresses.

“I tell patients that they may need re-treatment because CK does not turn the clock off, it just resets it,” Dr. Milne said. He said that this approach is based on what Dr. Durrie tells his patients, and it expresses the reality of what patients should expect.

“The part of the eye that is aging is not the cornea, which CK reshapes; but rather the lens of the eye, which will continue to age,” he added.

Patients may choose eventually to have a lens procedure to “turn the clock off,” but CK is a less invasive and excellent entry procedure for people who are interested in becoming less dependent on their glasses, he said.

Furthermore, it is important to establish the education and treatment plan with the patient, according to Dr. McDonald.

“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,” she said.

The usual factors such as history and information about their lifestyle must also be considered when determining a good CK candidate, she said.

Five critical skills

The five critical skills for successful CK with light touch are centration and marking; tip placement; steady hand; amount and consistency of pressure; and consistent and full depth throughout the delivery of the CK pulse, according to Dr. McDonald.

“If you remember only one thing, it’s to take 5 minutes to align and center the person properly; then it will take 1 minute to do the surgery,” she stressed. “Always center over the entrance pupil, turn off or dim all the other lights in the room so the patient isn’t looking somewhere else, and make sure you have vertical microscope alignment.”

A major reason for induced cylinder is a microscope moved out of alignment, she said.

“Most CK surgeons have a carpenter’s level attached to the flat area just behind the oculars, so that they can continuously check the perpendicularity of the microscope,” Dr. McDonald said.

Despite all of the successes with CK with light touch, she said that it is still a new idea, and additional research is required until its safety, efficacy and stability are established.

“However, everyone who has tried this [light-touch] technique once has switched immediately, and the number of times I’ve had to add a bonus spot for induced cylinder is dramatically decreasing. Actually, I haven’t added one yet since switching to the light-touch technique a few months ago,” she concluded.

For Your Information:

• Marguerite B. McDonald, MD, FACS, can be reached at 2820 Napolean Ave., Suite 750, New Orleans, LA 70115; 504-896-1240; fax: 504-896-1251. Dr. McDonald has no direct financial interest in the products mentioned in this article. However, she is a paid consultant for Refractec.
• H.L. Rick Milne III, MD, can be reached at 803-256-0641. Dr. Milne has no direct financial interest in the products mentioned in this article nor is he a paid consultant for any companies mentioned.

• Aleta Mayne is the Associate Editor of Ocular Surgery News, Latin America edition.