spotlight on technology & technique
Refractive Surgery Evolves Again
A new device combines the advantages of surface ablation and LASIK.
By Christopher Kent, Senior Associate Editor

Ever since the idea of using laser ablation to perform refractive surgery first appeared, individuals have searched for ways to perfect the procedure. Each new variation has raised the bar higher, but changing strategies have also introduced new problems. Those problems have, in turn, lead creative minds to develop still more improvements and variations.

One of those creative minds is Ioannis Pallikaris, M.D., Ph.D., professor and head of the Department of Ophthalmology at the University of Crete, Greece. Dr. Pallikaris is known for many accomplishments, including describing and naming the procedure of LASIK and being co-inventor of ray-tracing technology. In response to problems with LASIK, including the increasing incidence of iatrogenic ectasia and evidence that LASIK flaps may produce unpredictable biomechanical corneal changes, Dr. Pallikaris turned his attention to improving surface ablation procedures such as LASEK.

The Centurion SES EpiEdge epikeratome is one of two handpiece-and-blade sets that can be used with CIBA Vision's Centurion SES System.

Creating an Epithelial Sheet

His most recent invention, which Dr. Pallikaris calls a "subepithelial separator," or SES, is similar in appearance and function to a microkeratome, except that it substitutes a disposable, oscillating, PMMA block for the microkeratome blade. The PMMA block separates the softer epithelium, along with the basement membrane, from the stiffer Bowman's membrane as it crosses the eye.

The result is a very thin, hinged flap -- a sheet of epithelial cells, created without the use of alcohol. (Because alcohol is toxic to epithelial cells, removing it from a procedure such as LASEK results in faster healing and less pain for patients.) The flexible, plastic "blade" isn't sharp, so it can't cut into the stroma. Dr. Pallikaris has dubbed refractive surgery using this device "Epi-LASIK." (The suffix "epi-" is derived from the Greek word for superficial, or surface-based.)

CIBA Vision is now marketing Dr. Pallikaris' invention as the Centurion SES EpiEdge epikeratome. (CIBA Vision received FDA 510(K) approval for the device in early September and the CE Mark in October.) The EpiEdge epikeratome is one of two handpiece-and-blade sets that can be used with the Centurion SES System, introduced by CIBA Vision in the U.S. in April of this year. (The other set is a microkeratome for use in traditional LASIK procedures.)

Advantages of Epi-LASIK

As well as eliminating the use of alcohol from LASEK, this procedure has several other advantages:

► The epikeratome produces a precise, reproducible delamination of the epithelium -- more precise than current microkeratomes. Ac-cording to CIBA Vision, early clinical results indicate that Epi-LASIK produces fewer flap complications than a standard microkeratome.

► The flap separates below the basement membrane, thus preserving its integrity. (Electron microscopy has confirmed this.) When alcohol is used, the cleavage plane falls within the basement membrane.

Dr. Pallikaris believes that leaving the basement membrane intact provides much more stability and support for the epithelium. In addition, basal epithelial cells show no irregularities and the hemidesmosomes are not adversely affected by the procedure. In contrast, electron microscopy shows that LASEK epithelial flaps made using 18% ethanol for 25 seconds have fragmented hemidesmosomes and basement membrane remnants attached to basal epithelial cell membranes; the basement membrane layer shows discontinuous and irregular extracellular fragments.

► Unlike a LASIK microkeratome, the SES doesn't cut into the stroma. As a result, a free flap isn't the kind of major problem experienced with LASIK.

► Because the surgeon is replacing an intact epithelium, the worst complication likely to occur is a corneal abrasion. Risk of haze, striae and subepithelial debris is minimal.

► Studies using porcine eyes have shown that tissue is completely separated by the epikeratome, so reflection of the separated tissue requires minimal manipulation. (This could also make post-surgery healing easier.)

► Early trials have shown that patients have high-quality vision by the first day post-op.

	The EpiEdge epikeratome creates an epithelial sheet using a dull, flexible, plastic separator that can't cut into the stroma.

Feedback From the Field

Marguerite McDonald, M.D., who practices at the Southern Vision Institute in New Orleans, is one of a handful of surgeons with experience using the EpiEdge epikeratome. "I've been interested in the return to surface ablation for some time," she says, "for a number of reasons, including safety, patient preference for avoiding use of a knife, and the improved results of wavefront-guided ablation. This instrument is a very useful step in that direction."

According to Dr. McDonald, the EpiEdge epikeratome is easy to use. "It's just like a microkeratome, except that instead of a blade it has a flexible plastic separator with a dull edge that slips along under the epithelium, following the path of least resistance. It makes a beautiful hinged sheet every time. I recently spent a day in Mexico City with two other surgeons using the device; it never dug into the stroma, regardless of the surgeon's technique."

Although extensive clinical results are not yet available, the Greek team reports excellent outcomes. "The first few surgeons to use the device have been pleased with its performance," says Dr. McDonald, "and it's pretty clear from the early Greek data that these patients have less pain than PRK patients. However, we suspect that the proper post-op cocktail will still play some role in keeping these people happy and pain-free.

"The main issue we're dealing with right now is deciding the best way to manage the epithelial sheet, once it's made. Several methods work well, including irrigation, wiping with the Weck-cel, and letting the sheet cling to a contact lens, but we want to be able to recommend a specific method rather than several options."

Epi-LASIK vs. LASIK

Dr. McDonald notes that there are some striking differences between Epi-LASIK and LASIK. "If the epithelial sheet happens to tear off during Epi-LASIK -- which did happen twice out of 20 cases that day in Mexico City while we experimented with different "sheet management" techniques -- you can reposit the sheet. As long as you've made a mark that will enable you to tell whether the sheet is upside down or rightside up, you can simply put it back on the eye and cover it with a contact lens.

"Even if the epithelial sheet gets torn off and lost or destroyed, it's not a big problem. You put a contact lens on the eye, and you have either a "free sheet" LASEK or a PRK. Patients will see well the next day, and they'll have their little cocktail of meds to keep them comfortable. The epithelium will regrow in 4 or 5 days.

"On the other hand, if you have a bad microkeratome pass while making a LASIK flap, you have a devastating problem -- potential corneal blindness, potential lawsuit. It's a disaster all around."

Dr. McDonald also points out that Epi-LASIK will make it possible for many more doctors to offer refractive surgery to their patients. "You can't really do an occasional LASIK," she says, "because you have to have a fairly high volume to keep your skill set 'up to snuff' and keep your nurses and techs on their toes. But you can do an occasional Epi-LASIK and get great results, even if you only do one every few months. The risk/benefit ratio is very different.

"This will allow people who don't have a huge refractive practice to offer the best options to their patients."

For More Information

To learn more about Epi-LASIK or CIBA Vision's Centurion SES System, contact your CIBA Vision representative at (800) 845-6585, or visit www.cibavision.novartis.com on the Web.