April 2010

 

COVER FEATURE

 

Cataract Surgery

Femto lasers in cataract surgery


by Michelle Dalton EyeWorld Contributing Editor

 

Femto lasers: At a glance

• Femtosecond lasers for use in cataract surgery offer more precise and reproducible capsulorhexis • Differences in the platforms comes from how they opt to image the cataract • Femtosecond lasers for cataract surgery can also be used to create LRIs • Using the femtosecond laser in cataract surgery allows for easier emulsification of the cataract

 

Three different platforms all promise better safety, efficacy, and consistency

Femtosecond lasers With the femtosecond lasers, the capsulorhexis can be placed precisely where the surgeon wants Source: William W. Culbertson, M.D.

Remove the cataract

Aspiration alone can remove the cataract from the bag Source: William W. Culbertson, M.D.

Intraoperative OCT

Intraoperative OCT can help determine the relevant dimensions of the anterior chamber Source: William W. Culbertson, M.D.

Using lasers to perform certain parts of cataract extraction harkens back to the days when Nd:YAG for posterior capsulotomy was first introduced. These days, the interest in using lasers has increased, as three companies are developing or have brought femtosecond technology to the cataract surgeon. These new lasers have the means of not only removing the cataract, but of creating precise capsulorhexis and treating astigmatism via limbal relaxing incisions. The three companies working on these lasers are: LenSx Lasers (Aliso Viejo, Calif.), LensAR (Winter Park, Fla.), and Optimedica (Santa Clara, Calif.). EyeWorld spoke with the medical monitors or key investigators here in the U.S. about their roles in the development of these lasers. At this point, only the LenSx has clinical indications cleared by the Food and Drug Administration (FDA). The remaining two are still under investigation. Roger F. Steinert, M.D., Irving H. Leopold Chair and Professor of Ophthalmology, professor of biomedical engineering, and Director, Gavin Herbert Eye Institute, University of California, Irvine, Calif., notes the technology offers potential improvements in “many categories,” he said, including incisions, capsulorhexis, and nucleus softening. Using a femtosecond laser “makes some of the more difficult and unreliable parts of cataract surgery more precise and more dependable,” said William W. Culbertson, M.D., professor of ophthalmology, and director, Cornea and Refractive Surgery Services, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, Miami.

“First of all, the femtosecond laser in cataract surgery will be soon inevitable especially in premium lens implantation,” said Zoltán Zsolt Nagy, M.D., clinical professor of ophthalmology, Semmelweis Uninversity, Budapest, Hungary. “With the aid of this laser the surgeon can guarantee the exact diameter and centration of the capsulorhexis. We all know that the crucial point of phacoemulsification is the rhexis, which should be central, curvilinear and continuous.”

Safety, efficacy

According to Stephen G. Slade, M.D., director, Laser Center of Houston, Houston, and medical director, LenSx, the two main issues with any new laser are its efficacy and safety. “Efficacy may be more important, and it has more impact,” he said. “There’s vitreous loss in 4%-6% of cataract cases—I got those numbers by calling Abbott Medical Optics [Santa Ana, Calif.] and Alcon [Fort Worth, Texas] and determining the ratio of vitreous packs to surgical packs. So if 5% of the cases are breaking the capsule and creating vitreous loss, that’s something we’d like to change. We’re used to hearing the well-known surgeons get up on the podium and talk about their personal complication rates, in the very low single digits, but in the ‘real world’ we’re probably higher.”

Since the middle of February, Dr. Slade has been using the LenSx at his Houston center; at press time he had results from 8 patients. “They’re all 20/20 or 20/25 the next day,” he said. “These are very quiet eyes. This technology looks to me like IntraLase, except on a bigger scale.” One of the keys to all three of the laser platforms, and why several leading cataract surgeons are excited about their potential, is the automation these lasers can provide—in creating the capsulorhexis and in pre-chopping the nucleus, reducing the overall energy needed to remove the cataract. “The femtosecond is a more accurate, reproducible, natural evolution of this technology,” said John A. Vukich, M.D., surgical director, Davis Duehr Dean Center for Refractive Surgery, Madison, Wisc. “While cataract surgeons are doing a good job now, the femtosecond laser introduces the ability to be more consistent.” Dr. Vukich is a principal investigator for Optimedica, a company already known for its retinal lasers. “The field of femto laser technology has the potential to, in the simplest of terms, help automate many of the crucial steps of surgery,” said Louis “Skip” Nichamin, M.D., Brookville, Pa. “It’s a reproducible, safer operation to improve outcomes.” Using the femtosecond laser for incisions makes them more “precise and repeatable, and we believe they may be proven to self-seal more reliably,” Dr. Steinert said. “Astigmatic incisions can be programmed to be precisely repeatable, which should lead to greater accuracy.”

The beauty of these lasers is that “the capsulorhexis can be placed exactly where you want it to be, which is quite a difference from how we do it now,” Dr. Culbertson said. The value for cataract surgeons is in delivering a consistent end result, “and that allows the average ophthalmologist to do a better job,” Dr. Vukich said. “The adoption of this technology will be much quicker than the IntraLase was for LASIK.”

Dr. Culbertson agreed, saying that the capsulorhexis may be oval or oblong when created manually, which the surgeon will not realize until the IOL is implanted. “If the goal is to have a 0.5 mm overhang on the edge of the IOL, if you’re a half-millimeter off, 90 degrees of the circumference of the IOL will not be covered by the capsule,” he said, adding there are three potential sources for error in creating a capsulorhexis: the shape, the size, and the positioning. “In the more modern IOLs and IOLs to come, those variables will be more important,” he said. “Right now, we overcome any inconsistencies with smaller capsulotomies, but that can also make surgery more difficult.”

These femtosecond lasers “increase the safety, provide better outcomes, better efficiency, etc. It’s my opinion those will be the reasons cataract surgeons embrace the technology,” Dr. Nichamin said. The “brilliance” of these lasers is their ability to segment the nucleus into smaller fragments, “so all it takes is the aspiration alone to get the cataract out of the bag,” Dr. Vukich said. “Less energy is needed, you’re less likely to put stress on the zonules or traumatize the capsular bag, etc. The less manipulation you need to do, the better.”

Dr. Nagy added that while in most cases, surgeons can manually achieve a perfect rhexis, but that patients may inadvertently move, rendering the rhexis anything but perfect. He said younger patients are more anxious about premium lens implantation and are more likely to move during surgery. That can lead to lens tilt (even in aspheric lenses), which inevitably leads to higher order aberrations, leaving the patient with a post-op visual acuity that is not as good as it could be, he said. “Think of it like this … imagine if you could always place your incision in the same exact place, with the same exact size, and the same exact architecture every time, and control astigmatism on top of it. You’ll inevitably have better results,” Dr. Slade said.

Accuracy of the lasers

The lasers can also be used to soften the nucleus before removal, Dr. Steinert said. “In many cases, the entire lens can be simply aspirated, with little to no ultrasound power. As a result, the safety and efficiency of the lens removal should markedly improve,” he said. Because the laser procedure is being performed before “any surgical entry, the open-eye time is reduced with increased safety as well as surgical efficiency,” Dr. Steinert said. Saying the average cap diameter in terms of shape “has been very inaccurate through the years, and we’ve just accepted it. But now we don’t have to; these lasers are precise down to the micron level instead of millimeters,” Dr. Culbertson said.

With the Optimedica laser, Drs. Culbertson and Vukich said they are “within 0.1 mm in terms of intended diameter. It’s like night and day compared to a manual capsulorhexis.” Data from the LensAR study “showed significant improvement in capsulorhexis accuracy,” Dr. Nichamin said. “We were able to quantitate how much better the rhexis was in terms of symmetry and size. My personal experience supports those findings as well. I used the same laser in Mexico on a number of eyes and my results were identical.”

With “absolutely” no doubt these lasers are more accurate, Dr. Slade said “you’re asking if a laser can draw a circle more precisely than a surgeon with a bent needle.”

Using a femtosecond laser will “not only make the procedure safer, but it decreases the amount of phaco energy,” Dr. Nagy said. “We can cut the lens into four quadrants without any phaco energy, so the temperature rise will be lower, which is good for the endothelial cells.”

There is a “great deal of variability” in how surgeons create wounds, Dr. Nichamin said, and that variability lies directly in the surgeon’s hands. “We know the best wound architecture is square, that they’re far more stable and strong than rectangular wounds. These lasers can be programmed to reproduce the ideal wound structure which will reduce the incidence of wound problems,” he said. “With clear corneal incisions, these femtosecond lasers will allow us to have safer and more stable incisions.”

Platform differences

Because two of the lasers have not yet received FDA approval, most of the details are considered proprietary, the investigators said. “They’re all equivalent in terms of the concept,” Dr. Vukich said. “They all provide more accurate cuts and capsulorhexis than you can do manually.”

Some of the basic differences are how the lasers image the ocular structures to focus in three-dimensions the direction of the laser energy, Dr. Nichamin said. “LenSx is using optical coherence tomography,” he said, adding the LensAR is using Scheimpflug imaging, “which may or may not offer potential advantages.”

Dr. Culbertson added the Optimedica laser “uses real time intraoperative OCT [optical coherence tomography] visualization to determine the relevant dimensions of the anterior chamber and the thickness of the cornea and the lens.”

Pricing considerations

Most anterior segment surgeons have recognized “the safety and stability of using the femtosecond laser in LASIK, and it’s a short extension to see its benefits for cataract surgery,” Dr. Culbertson said. Cost considerations are likely to be rationalized because “it’s a safer and more effective operation,” Dr. Nichamin said. Because the technology has the potential to lend itself to LRIs by addressing lower levels of astigmatism, “surgeons who weren’t completely comfortable with a diamond blade can now treat patients with a laser,” he said.

Although cataract surgeons will not be able to pass along any costs associated with the cataract removal to Medicare patients, they would be able to pass along any refractive procedures performed with the laser (such as limbal relaxing incisions), Dr. Nichamin said. Patient acceptance of femtosecond technology during cataract surgery is going to drive the demand, Dr. Slade predicted. “They think we’ve had lasers forever; patients instantly got the messaging with the IntraLase and LASIK, and I think they’ll follow suit with these,” he said. The femtosecond laser “will revolutionize the premium lens industry,” Dr. Nagy said, agreeing that patient demand will be the driving force for rapid surgeon acceptance. These lasers “facilitate premium implants,” Dr. Vukich said. “Patients want the best implant and want the best laser possible for those implants. You’ll need a viable financial model to justify the purchase, but it will provide an upstream benefit.”

“LASIK didn’t succeed because surgeons wanted to buy more lasers,” Dr. Slade said. “At some point, it became patient-driven, and the same dynamic will come into play with this technology.”

Edtiors’ note: Drs. Steinert, Nagy, and Slade have financial interests with LenSx (Aliso Viejo, Calif). Dr. Culbertson has financial interests with Optimedica (Santa Clara, Calif.). Dr. Vukich has financial interests with Optimedica (Santa Clara, Calif.). Dr. Nichamin has financial interests with LensAR (Winter Park, Fla.).

Contact information

Culbertson: 305-326-6364, wculbertson@med.miami.edu
Nagy: nz@szem1.sote.hu
Nichamin: 814-849-6547, ldnichamin@aol.com
Slade: 713-626-5544, sgs@visiontexas.com
Steinert: 949-824-8089, steinert@uci.edu
Vukich: 608-282-2000, javukich@facstaff.wisc.edu

Femto lasers in cataract surgery Femto lasers in cataract surgery
Ophthalmology News - EyeWorld Magazine
283 110
216 217
,
2017-04-06T10:07:04Z
True, 4