Laser market provides valuable options for low levels of hyperopia

Regression may be a thing of the past as developments continue in laser and laser-like procedures for hyperopia.

Issue: October 15, 2001

The history of laser and laser-like surgical procedures for the correction of hyperopia has been checkered at best. Hot-needle thermal keratoplasty failed, as did the original version of contact laser thermal keratoplasty. Haze and regression marred early attempts at hyperopic photorefractive keratectomy (PRK). Each procedure could be counted on to correct some degree of hyperopia, but long-term stability, quality of vision and patient comfort were elusive.

As marketable hyperopia correction procedures, these early techniques left much to be desired. As building blocks for today’s more effective techniques, they were unparalleled. Today, hyperopic LASIK achieves uncompromised outcomes in patients up to +3 in the United States and up to +5 in Canada.

Sunrise Inc.’s recently approved laser thermal keratoplasty (LTK) provides a cost-effective, holmium laser-induced collagen shrinkage fix for hyperopes requiring 1 to 1.5 D of correction. With positive outcomes resulting from 2 years of clinical trials, conductive keratoplasty (CK) appears to have advantages over both procedures. CK uses high radio frequency energy, delivered with a thin metal tip in concentric rings of multiple spots around the periphery of the cornea, to shrink collagen and steepen the center of the cornea. This technology is manufactured by Refractec.

PRK and LASIK

In an interview with Ocular Surgery News, Canadian refractive surgeon Robert J. Mitchell, MD, described his experiences providing PRK and LASIK to approximately 400 hyperopic patients during the past 5 years.

“When we started doing hyperopic PRK in 1994, we achieved good results initially, but then we started [experiencing complications] in about two out of 10 patients,” he said.

In response to that, Dr. Mitchell began cutting back on the degree of hyperopia he would treat. He began treating as much as 8 D of hyperopia with PRK, but eventually scaled back.

“Not every patient over that range gets into trouble, but enough do that it’s not worthwhile doing it. I concluded that I should stay lower in my hyperopic PRK correction. The +1, +2 and +3 do well and the +4 and +5 still do fine, but after that watch out,” he said.

Dr. Mitchell switched to LASIK for hyperopic patients in 1995.

“By going over to LASIK we found that we had virtually no regression — certainly nothing compared to PRK. We didn’t get the haze that we got with PRK and we didn’t get those central nodules that you could get with the high PRK correction. So LASIK for hyperopia was a big improvement over PRK,” he said.

Dr. Mitchell attributes much of his success with hyperopic LASIK to his use of a flying-spot, third-generation Asclepion-Meditec MEL70 excimer laser, which he says provides excellent centration, and a third-generation Moria microkeratome, which he adds has made his life “infinitely easier.” With this combination, Dr. Mitchell is confident providing LASIK to patients with up to 5 D of hyperopia.

“After that I chicken out,” he said.

LASIK and LTK

David R. Hardten, MD, offers LTK to hyperopic patients and is an investigator in the CK clinical trials as well. However, the procedure he uses most frequently to treat hyperopia is LASIK.

“LASIK works very well for hyperopia and hyperopic astigmatism,” he said. “The vast majority of patients want rapid visual recovery and minimal induced myopic shift followed by regression back to the point of stability, and they get this with LASIK.”

He said he uses LTK mostly for monovision treatments.

“With LTK, you take a +1 patient and make him or her –3. Then they go back to plano over a year or two. So the percentage of induced nearsightedness you get with LTK is even greater, and that’s why most of us limit our use of LTK to 1 D and below in patients in an older age group who will appreciate the near vision they get,” he said.

The two primary issues in hyperopic LASIK, according to Los Angeles refractive surgeon Robert K. Maloney, MD, are dry eye syndrome and quality of vision.

“Dry eyes are related to severing nerves, and quality of vision is related both to changes in the ocular surface and the amount of irregular astigmatism you leave after the laser treatment,” he said.

A tracking laser, such as the Visx Star S3, is crucial to hyperopic LASIK because of the size of the optical zone needed in these patients, he suggested.

“We started using the Visx S3 Star ActiveTrak laser about a year ago, and since then our results for hyperopia are significantly better.”

LASIK and CK

Dr. Maloney, a long-time LASIK proponent and also a CK investigator who has performed more than 50 of the radio frequency collagen shrinkage procedures, says not only does CK appear to provide as good an outcome as LASIK, but it may also do even better. It has advantages over LTK as well, he pointed out.

“The advantage of CK compared to LTK is that it appears to be permanent. It doesn’t seem to wear off. We now have data out to 2 years, and it indicates that regression the first year after CK is the same or less than LASIK,” he said.

So, he suggested, CK is as stable as LASIK. CK uses a probe that penetrates 450 µm into the cornea, delivering radio frequency energy deep into the cornea. According to Dr. Maloney, it appears that this depth of penetration is what gives CK its stability.

“The accuracy of CK appears to be equivalent to LASIK as well, in terms of percentage of eyes within 0.5 D of emmetropia and percentage of eyes seeing 20/20. We think that CK is best for 3 D of hyperopia or less, and that seems to be the range where LTK is most effective as well,” he said.

According to Dr. Maloney, so far CK has also exhibited advantages over LASIK.

“With CK, we have not seen the hazy vision and dry eyes that sometimes accompany hyperopic LASIK. None of the patients in my subset of the study had dry eye after CK. None complained of blurry or hazy vision or double vision. Those are rare complaints after hyperopic LASIK, but they’re significant. So a potential advantage of CK is that it gives better quality of vision than hyperopic LASIK and better patient comfort,” he said.

However, recovery with CK is slightly slower than with LASIK; the eyes are a little more uncomfortable during the first 24 hours and a bandage contact lens should be placed on the eye to maintain comfort.

“CK patients, like LASIK patients, have an initial overshoot. They are initially myopic and then over the next few weeks to a month they regress to emmetropia,” he said.

One advantage of CK, he said, is that you can do it with the patient sitting up at the slit lamp.

“It’s easier than doing LASIK,” he said, “It really is an in-office procedure.”

Dr. Maloney admits to sounding like a CK cheerleader, but he says he didn’t start out this way.

“When I started the clinical trials, I was skeptical because we’d failed with various versions of thermal keratoplasty so many times, ” he said.

“The old hot needle thermal keratoplasty didn’t work, the original version of contact LTK didn’t work. The Sunrise noncontact LTK worked, but then there was significant regression. So when I started the CK trial I really didn’t expect to see a permanent effect. In fact, when I agreed to participate in the trial I did it with the understanding that the procedure was free and the patients were paid for their participation because I wasn’t at all confident that there was a benefit. But in fact, the patients did great, and these patients referred other patients for the clinical trial, which is very unusual.”

Dr. Maloney and Marguerite B. McDonald, MD, presented phase 3 clinical trial outcomes of CK for the treatment of hyperopia in 400 eyes earlier this year at the American Society of Cataract and Refractive Surgery meeting.

Dr. Maloney presented interim results of the trial, which at the 9-month follow-up found that uncorrected visual acuity was 20/20 or better in 60% and 20/40 or better in 96% of the eyes treated. Also, 60% of the eyes were within 0.5 D of intended correction and 80% were within 1 D. There were no adverse events or complications at 9 months.

Dr. McDonald reported that at 12 months, 51% of eyes were at 20/20, 73% were at 20/25 and 91% were at 20/40 or better. Vision was stable at 6 months.

For Your Information:

Robert J. Mitchell, MD, can be reached at 705 Chinook Center, 6455 MacLeod Tr. SW., Calgary, AB, Canada T2H-OK9; (403) 258-1773; fax: (403) 258-2704.
David R. Hardten, MD, can be reached at 710 E. 24th St., Suite 106, Minneapolis, MN 55404; (612) 813-3600; fax: (612) 813-3658; email: dhardten@mneye.com.
Robert K. Maloney, MD, can be reached at 10921 Wilshire Blvd., Suite 900, Los Angeles, CA 90024; (310) 208-3937; fax: (310) 208-0169; e-mail: drmaloney@maloneyvision.com.
Sunrise Technologies can be reached at 3400 W. Warren Ave., Fremont, CA 94538; (510) 771-2389; fax: (510) 771-2292; Web site: www.sunrise.md. Refractec Inc. can be reached at 3 Jenner, Suite 140, Irvine, CA 92618; (949) 784-2600; fax: (949) 784-2601.