FDA approves AquaFlow

With a batch of new instruments at their disposal, surgeons are increasingly showing interest in epi-LASIK, the latest variation in laser refractive surgery.

It was more than 3 years ago that Massimo Camellin, MD, described laser epithelial keratomileusis, or LASEK. That was an early sign of surgeons' interest in returning to excimer laser surface ablation for refractive surgery.

While LASIK is still by far the most frequently performed refractive surgical procedure, interest in surface-based approaches has grown steadily since the introduction of LASEK. At first a number of surgeons learned Dr. Camellin's alcohol-based technique and then introduced variations of their own. Soon, though, a separate and distinct technique began to emerge, employing a microkeratome-like device rather than alcohol to loosen the epithelial sheet.

Epi-LASIK flap is created using the VisiJet EpiLift device (left). An eye 1 day after epi-LASIK (right). Images: Lohmann CP

Now there are at least three devices on the market for use in epi-LASIK, and with the variety of choices has come increased interest in and use of the technique.

Back to the surface

With almost a decade of experience with mid-stromal ablation in LASIK, why are surgeons once again showing interest in corneal surface ablation?

PRK, the first form of excimer laser corneal surface ablation, was described in the late 1980s and widely adopted by refractive surgeons. But when LASIK was introduced in the 1990s, PRK quickly lost popularity to the microkeratome-based procedure, seemingly for a number of reasons.

The principal reason for the move from PRK to LASIK seemed to be the reports of patient discomfort or pain with PRK. The 3 or 4 days between laser treatment and re-epithelialization were difficult for some patients, and there were reports of patients unwilling to have a second eye done because of the pain they experienced with the first.

Another reason for the abandonment of PRK was its lengthy visual recovery. Patients often took up to 6 months to reach a stable refraction, a definite disadvantage for a procedure being paid for out of pocket.

A perhaps more political reason for the move to the microkeratome-based procedure may have been the "bladeless" aspect of PRK surgery. During PRK's heyday in the early 1990s, there was talk in optometric circles about the fact that technicians were programming the lasers for refractive surgery. What was the surgeon's role? If techs could program the laser, so could optometrists.

The appearance of LASIK seemingly solved all these problems at once. With ablation performed under a stromal flap, there was no need for epithelial removal and therefore no painful re-epithelialization period. The time to visual stabilization after LASIK, even in the earliest reports, seemed to be days rather than months. And LASIK involved the use of a sophisticated microkeratome, taking it definitively out of the domain of optometry.

New reasons

So what is now drawing surgeons away from LASIK and back to ablation of the stromal surface? After a decade of experience with LASIK, some limitations have been recognized.

Porcine cornea histology shows an intact epithelial fl ap fl ipped back at the hinge. Flap created with the epikeratome blade of the Amadeus II (Advanced Medical Optics). Image: Sarra G-M

One is a limit to the depth of ablation. Theo Seiler, MD, and others have suggested that the residual stromal bed after LASIK ablation should be no less than 250 µm thick because of the risk of corneal ectasia with a thinner bed. With a mean corneal thickness of 550 µm and microkeratome flaps sometimes approaching 200 µm in thickness, this does not always leave room for the degree of ablation needed for higher refractive errors. Elimination of the stromal flap, as in epi-LASIK, solves this problem.

Another drawback of LASIK is the potential for microkeratome complications. Buttonholes, free caps, thin flaps, ocular penetration, all are possible with use of a microkeratome to create a flap.

A third drawback, described by Eric D. Donnenfeld, MD, and others, is the possibility of LASIK-induced dry eye. These authors noted that LASIK flap creation transsects the long posterior corneal nerves, significantly reducing corneal sensation. They suggested that the nerves may not heal for 6 months or more, resulting in dry eye signs and symptoms in post-LASIK patients. More recent reports by Martha P. Calvillo, MD, and colleagues using confocal microscopy suggest that the nerves may not be healed even at 3 years.

All these factors are cited as reasons for a return to the corneal surface.

But why not LASEK?

A number of surgeons have adopted LASEK and have reported good results, but there has not been a mass movement of surgeons to the procedure to date. If this is so, why are surgeons showing an interest in epi-LASIK?

Chris P. Lohmann, MD, of Regensburg, Germany, has one of the largest case series in the world with epi-LASIK. He said he believes the epikeratome-based procedure has distinct advantages over alcohol-based LASEK.

Epi-LASIK is more standardized than LASEK and less painful for the patient, Dr. Lohmann said.

In the LASEK technique as originally described, the epithelium is loosened by application of alcohol, and a blunt instrument is used to move the epithelium to the side of the cornea in a sheet. After excimer laser application, the epithelial sheet is stretched back across the cornea. There is no microkeratome cut.

Reports of LASEK results often cite reproducibility of the epithelial flap as a potential problem.

Dr. Lohmann said he thinks problems such as pain and haze following LASEK are related to problems with the creation of the flap. He said the use of an epikeratome — in his case the EpiLift System, manufactured by Gebauer and distributed by VisiJet — makes the procedure more predictable, more comparable to LASIK.

Dr. Lohmann said epi-LASIK is now his "standard technique in excimer laser refractive surgery."

Even Dr. Camellin, the developer of LASEK, is showing interest in what he called its "sister," the epi-LASIK procedure. In an e-mail interview he said he is not "abandoning LASEK in favor of epi-LASIK," but he is investigating all the epikeratome devices one at a time. He has begun with the Centurion SES Epikeratome from Norwood EyeCare.

Dr. Camellin noted that "the basis of the techniques LASEK and epi-LASIK are the same, that is, the conservation of an epithelial flap."

He said that, while he does not have a long personal follow-up with the epi-LASIK procedure, he feels the real advantage of epi-LASIK is that it allows all surgeons to create a good flap regardless of their level of surgical skill with the procedure.

Richard L. Lindstrom, MD, noted that epi-LASIK has advantages and disadvantages in comparison to LASIK.

"They are similar in difficulty," he said. "The range of correction seems to be the same if topical mitomycin is used. Epi-LASIK appears to be less comfortable than LASIK for the patient, with slower visual recovery."

One advantage of the surface procedure may be better postop vision, Dr. Lindstrom suggested. Epi-LASIK has a similar quality of vision to PRK, which may be superior to LASIK, he said.

Devices for epiLASIK EpiLift System Distributed worldwide by VisiJet, manufactured by Gebauer FDA 510(k) approval received September 2004 Visijet Inc. 192 Technology Drive, Suite Q Irvine, CA 92618 U.S.A. +1-949-450-1660 fax: +1-949-453-9652 www.visijet.com Centurion SES Epikeratome with EpiEdge Distributed by Norwood EyeCare FDA 510(k) approval received in 2003 Norwood EyeCare 6455 East Johns Crossing Suite 425 Duluth, GA 30097 U.S.A. +1-678-720-0698 fax: +1-678-720-0710 epi-lasik@norwoodeyecare.com www.norwoodeyecare.com Moria Epi-K Distributed by Moria Not for sale in the United States Moria Inc. 1050 Cross Keys Drive Doylestown, PA 18901 U.S.A. +1-215-230-7662 fax: +1-215-230-7670 moriausa@moriausa.com www.moriausa.com

Dr. Lohmann said he switched to epi-LASIK not because the results were better, but because epi-LASIK gives him consistency.

"I know that the results I have here, everyone else will also get with a little training," he said.

Dr. Lindstrom is a newcomer to the epi-LASIK technique. He has done only one case using the VisiJet EpiLift. He said the learning curve appears to be short.

"It made a perfect flap," even on that first case, Dr. Lindstrom said. "The recovery period pain is similar to LASEK, and the recovery of vision is similar as well. The flap is, however, easier to make than a good LASEK flap."

A note from the editors:

Advanced Medical Optics has an epikeratome blade in development for the Amadeus II microkeratome. The blade may be available in the United States and Europe in the second quarter of 2005, an AMO official said.

For Your Information:

• Chris P. Lohmann, MD, can be reached at the University Eye Clinic, Franz Josef Strauss Allee, Regensburg 8400 Germany; +49-94-1-944-9201; fax: +49-94-1-944-9202.
• Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 106, Minneapolis, MN 55404 U.S.A.; +1-612-813-3600; fax: +1-612-813-3660.
• Massimo Camellin, MD, can be reached at Via Dunant 10, Rovigo 45100, Italy; phone/fax: +39-042-541-1357.
• VisiJet Inc. can be reached at 192 Technology Drive, Suite Q, Irvine, CA 92618 U.S.A.; +1-949-450-1660; fax: +1-949-453-9652; Web site: www.visijet.com.
• Norwood EyeCare can be reached at 6455 East Johns Crossing, Suite 425, Duluth, GA 30097 U.S.A.; +1-678-720-0698; fax: +1-678-720-0710; e-mail: epi-lasik@ norwoodeyecare.com; Web site: www.norwoodeyecare.com.
• Moria Inc. can be reached at 1050 Cross Keys Drive, Doylestown, PA 18901 U.S.A.; +1-215-230-7662; fax: +1-215-230-7670; e-mail: moriausa@moriausa.com; Web site: www.moriausa.com.

References:

• Calvillo MP, McLaren JW, et al. Corneal reinervation after LASIK: Prospective 3-year longitudinal study. Invest Ophthalmol Vis Sci. 2004;45:3991-3996.
• Donnenfeld ED, Solomon K, et al. The effect of hinge position on corneal sensation and dry eye after LASIK. Ophthalmology. 2003;110(5):1023-1029.
• Seiler T, Koufala K. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg. 1998;14(3):312-317.
• Tim Donald, ELS, is the OSN Copy Chief.