Read the January issue of Refractive Surgery Outlook
Femtosecond Laser: Positive Results, Wider Uses
By Linda Roach, Contributing Writer
Scoffed at just a few years ago as an overpriced microkeratome, the femtosecond laser is convincing even former skeptics that it may well write a new chapter in the story of ophthalmic surgery.
At the fall ISRS Annual Meeting, during Subspecialty Day before the AAO Joint Meeting with PAAO, the evidence in favor of new surgical uses for this high-tech tool was abundant; and the buzz it created a testament to its growing popularity worldwide.
Attendees at the ISRS meeting heard positive reports from researchers who have tested ophthalmic femtosecond lasers for much more than making LASIK flaps, including:
- Every phase of cataract surgery in which tissue is cut or altered.
- Reshaping the cornea without disturbing the ocular surface.
- Limbal relaxing incisions to correct small amounts of astigmatism.
- Restoration of accommodation by cutting structural fibers in the crystalline lens to make it more flexible.
Advice: Cautious Skepticism
"Most refractive surgeons were pretty skeptical when the ophthalmic femtosecond laser first came out. I certainly was," recalled Richard L. Lindstrom, MD,¹ in an interview with Refractive Surgery Outlook. "But then we got our first Intralase (AMO) and began cutting LASIK flaps with it. We could measure the advantages. In large practices, we could see the reproducibility of results between surgeons, and the lower complication rates."
Surgeon’s growing acceptance of the femtosecond laser is evidenced in the 2009 ISRS annual survey of U.S. refractive surgeons, which showed 52 percent of respondents (n=134) identified the femtosecond laser as their preferred device for cutting LASIK flaps.²
It's a Laser Knife
"Now, I think of the femtosecond laser as a very controllable laser knife," Dr. Lindstrom said. "Any procedure for which we currently use a sharp knife or a blade, we can consider using it."
Ronald R. Krueger, MD,³ believes the femtosecond laser is becoming the new scalpel for eye surgery and advises persistent skeptics to keep their minds open. “A lot of people would say, 'Why do I need a femtosecond laser? I get good results without it.' That's just like what everybody said to Charlie Kelman about phaco," Dr. Krueger said. "But if the femtosecond laser is really making cataract surgery more precise, so you can avoid the known complications and make it safer, then we have an obligation to pursue it for our patients."
VisuMax: An 'All-in-One' Method of Refractive Correction
The VisuMax femtosecond laser (Carl Zeiss Meditec) can replace both the mechanical microkeratome and the excimer laser in myopic refractive surgeries, without an extended learning curve, according to an Indian surgeon who has performed hundreds of these "all-in-one" femtosecond surgeries.
Rupal Shah, MD,4 delivered her much-anticipated report at the ISRS meeting in which she described her experience using the VisuMax to carve precisely shaped intrastromal lenticules. They are removed by lifting a flap (called FLEx) or through a 4 to5 mm incision ("SMILE"). She has used this technique in 477 eyes.
Good Outcomes, Quickly
"What was most surprising for me were the amazing refractive outcomes. Less than a thousand eyes have been done worldwide, yet the refractive outcomes are as good as with an excimer laser on which millions of procedures have been done," Dr. Shah said in an interview with Refractive Surgery Outlook.
Dr. Shah reported on 477 all-femtosecond surgeries to correct myopia of -0.50 D to -10.0 D (mean: -4.30 D ± 2.01 D); she had follow-up data for six months on 253 eyes; three months on 350; and one month on 477. The results included:
- Accuracy: 93 percent of eyes were within ± 0.5 D of the refractive target at six months.
- Post-op UCVA: 67 percent of eyes were 20/20 or better at six months. Before surgery 65 percent could see 20/20 corrected. (Early results with a new 500 kHz VisuMax indicate it might improve the number of patients seeing 20/20 uncorrected after surgery to nearly 90 percent at one week, Daniel Reinstein, MD,5 reports.)
- Visual recovery: At one month, 19 percent of eyes showed a BSCVA loss of -1 line. After Zeiss adjusted the laser's scan pattern, this improved significantly (one month after surgery: -1 line, 5 percent; -2 lines, 1 percent), Dr. Shah said.
Procedure Minimizes Aberrations
- Induced aberrations: Total levels of higher-order aberrations rose only slightly after the procedure -- a big contrast with excimer-laser surgeries.
- Stability: Minimal change in refraction between one week post-op and six months.
- BSCVA: At six months, this was the same as or better than preop in 92 percent of eyes, while 26 percentgained one line, and 4 percent gained two lines.
- Lost BSCVA: Overall, 5 percent lost one line at six months; 3 percent lost two lines.
- Adverse events: Two eyes developed grade 1 haze and three had diffuse lamellar keratitis. All resolved without complications. There were seven procedures with suction loss; one case was aborted.
FEMTEC: An Intrastromal Fix for Presbyopia?
What if a refractive surgeon could reshape the cornea by weakening its biomechanical structure, without cutting through the epithelium, endothelium, Bowman’s membrane or Descemet’s membrane? That capability, combined with the concept of a multifocal cornea, led to the intraCOR ® procedure for alleviating presbyopia using the FEMTEC laser (Technolas Perfect Vision, Heidelberg, Germany).
Six-month results from a prospective, fellow-eye-controlled clinical trial so far support the safety and efficacy of treating presbyopia in this way, according to Gerd U. Auffarth, MD,6 of the University of Heidelberg.
Spectacle Independence in 16 of 25
The 25 emmetropes in the study showed mean near-VA gains of 4.29 lines (logMAR) in the treated eye, without any loss of distance acuity, Dr. Auffarth said. Mean near VA on the logMAR scale improved from 0.7 (20/100) before surgery to 0.27 (20/33) afterward (p < 0.01). Sixteen patients reported reading without spectacles. Yet UCDVA was stable (mean 0.11 logMAR pre-op; 0.12 post-op).
The 20-second intraCOR treatment placed pulses of laser energy in concentric circles around the visual axis (depth >100 ?m), with the goal of producing ? +2D of add. The laser pattern created a hyperprolate cornea by severing stromal fibers, which allowed the central cornea to move anteriorly. The bubbles of vaporized tissuefaded by 1 week.
Hints About Long-Term Refractive Stability
Although these patients require longer follow-up, another research group's 12- to 18-month results with intraCOR suggest that the refractive gains might last. Sinan Goker, MD,7 et al. reported stable VA at one year and beyond in 336 eyes (180 of them presbyopic) treated with intraCOR. Patients were corrected for hyperopia (n=302) and post-surgical residual refractive error (34), in addition to presbyopia as needed.
Near VA was J1 or J2 in 70.3 percent; J3-J5 in 20.6 percent; and J5-J7 in 9.1 percent. Twelve eyes (6.45 percent) lost one line of BCVA, and 3.2 percent lost two or more lines. The most common complication was glare and haloes at night, especially if the treatment zone was decentered >1 mm, Dr. Goker said.
LenSx: 'No-Touch' Laser Treatment Can Liquefy the Lens
Last September the femtosecond laser officially moved into the arena of cataract surgery in the U.S., with the approval of the LenSx 550 (LenSx Lasers, Aliso Viejo, CA) for capsulotomy. But the company and its competitors hope to transform this first step in femtosecond-assisted cataract surgery into a stampede.
LenSx is conducting international clinical trials of its femtosecond laser to assist or replace two other manual parts of cataract surgery: chopping and liquefying the lens, and making optically-optimized corneal incisions. The company has not released detailed data on these trials, but two ISRS presenters shared general results.
Zoltan Nagy, MD,8 reported that after "no-touch" pre-treatment of the lens with femtosecond energy, soft nuclei were completely liquefied. The emulsified lens could then be removed with an I/A tip.
In Denser Cataracts, the Laser Does the Pre-Chopping
In harder lenses, Dr. Nagy used the laser to pre-chop the nucleus into quadrants. Manual tools easily separated the sections before ultrasonic phacoemulsification. Overall, the femtosecond laser pre-treatment reduced the average peak phaco power by 51 percent, and the effective phaco time by 43 percent, reported Stephen Slade, MD,9 medical director for LenSx.
In Dr. Nagy's study of more than 125 eyes, the capsulorrhexis diameter was within ±0.25 mm of the intended size in 100 percent of the laser cases, compared to 10 percent for manual capsulotomies. There were no radial tears. The biplanar corneal incisions were reproducible, and had precise dimensions and geometry. OCT at two weeks post-op showed tight closure, Dr. Nagy said.
LensAR: Cataracts and Presbyopia Are On Their Radar
The LensAR femtosecond laser is undergoing a 50-eye, controlled clinical trial for laser capsulotomy in Mexico City. A second clinical trial , led by Harvey Uy, MD, is underway in the Philippines will study the laser's capability for other cataract surgery steps and for correcting presbyopia.
In the Mexico trial, 50 patients underwent laser capsulotomy in one eye, and manual capsulotomy in the contralateral eye when bilateral surgery was required(n=24). The study found greater accuracy of size (p=0.005) and better consistency of shape (p=0.032) in the capsule buttons incised by the laser, said Dr. Louis Nichamin, MD.10
Diameter Variation Cut In Half
The laser-cut buttons were a mean of 0.219 ± 0.204 mm of the intended diameter. This compared to 0.492 ± 0.463 mm for manually created capsule buttons. The improvements appear to be largely independent of surgeon experience, Dr. Nichamin added.
Since 2004, LensAR has also conducted preclinical evaluations of what could prove to be a controversial proposition for alleviating presbyopia: increasing the flexibility of the clear, crystalline lens by treating it with the femtosecond laser. Treatment did not cause cataracts in rabbit and monkey eyes, Ramon Naranjo-Tackman, MD,11 reported at ISRS.
Optimedica: Results From a Clinical Feasibility Trial
The best possible visual results with premium intraocular lenses will not be achieved until the manual parts of cataract surgery can be done with more precision and repeatability, Jonathan H. Talamo, MD,12 said at ISRS. And the solution might lie in femtosecond-assisted surgery.
To that end, Dr. Talamo worked with Optimedica (Santa Clara, CA) to evaluate the company's prototype femtosecond laser in 40 human eyes. The treatment software and docking device are proprietary, and the laser features real-time OCT registration of the cornea, pupil and lens. Using real-time OCT helps avoid errors related to globe tilt or eccentric docking of the laser to the eye, ensuring that laser treatment to the lens and capsule is both appropriately centered and safely away from delicate structures such as the iris, anterior capsule and posterior capsule. Additionally, the depth of corneal incisions can be carefully calibrated because any changes in corneal thickness introduced by hydration or dehydration can be accounted for immediately prior to laser treatment.
The procedures were performed without complications at Centro Laser in Santo Domingo, Dominican Republic. Surgeons there used the laser to make precisely shaped, clear corneal incisions, capsulorrhexis, nuclear segmentation and nuclear softening prior to phacoemulsification.
Surgeons cut Z-shaped entry wounds that could seal tightly post-op, he said. The capsulotomies were within ± 0.1mm of the intended diameter, and the edges were smooth, Dr. Talamo said.
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1- Dr. Lindstrom is a Minnesota refractive surgeon. He has a financial interest in and has received fees from LensAR. Abbott Medical Optics (AMO), Alcon Laboratories, and Bausch & Lomb Surgical have paid him fees and/or royalties
2- Duffey RJ, Leaming D. US Trends in Refractive Surgery: The 2009 ISRS Survey. (Free PowerPoint available.)
3- Dr. Krueger is the director of refractive surgery at the Cole Eye Institute of Cleveland Clinic in Ohio. He has a financial interest in LensAR, and has received fees from Alcon Laboratories and Calhoun Vision.
4- Dr. Shah is clinical director at New Vision Laser Centers, of Mumbai and Vadodara, India. She received study support, consulting fees and travel support from Carl Zeiss Meditec.
5- Dr. Reinstein is medical director of London Vision Clinic in the UK. Dr. Reinstein is a consultant for Carl Zeiss Meditec.
6- Dr. Auffarth is a professor and acting chair of ophthalmology at the University of Heidelberg. He has performed contract research for several ophthalmic companies, including Technolas Perfect Vision.
7- Dr. Goker is in private practice at Istanbul Surgery Hospital in Istanbul, Turkey.
8- Dr. Nagy is a professor of ophthalmology at Semmelweis University, Budapest, Hungary. He is a consultant to LenSx Lasers.
9- Dr. Slade is a Houston, Texas, refractive surgeon and medical director of LenSx Lasers.
10- Dr. Nichamin is medical director of Laurel Eye Clinic, Brookville, PA., and a LensAR consultant.
11- Dr. Naranjo-Tackman is a professor of ophthalmology at the Universidad Nacional Autonoma de Mexico. He receives consulting fees from LensAR and is principal investigator for its Mexico City studies.
12- Dr. Talamo is a cataract and refractive surgeon in Waltham, MA. He has an equity interest in Optimedica and is a consultant for the company.
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