EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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24 EW CATARACT January 2014 Device focus Can femtosecond lasers live up to the hype? by Michelle Dalton EyeWorld Contributing Writer A panel discussion during the American Academy of Ophthalmology meeting suggests they can between the two techniques in VA, intended vs. achieved refraction, IOP, or flare meter measurements. "We had postulated that after using the laser the inflammation may be a bit higher, but that was not the case," he said. Dr. Holzer said with very few differences between the two techniques, he believes the main advantage of the femto is "the wide field of application in cataract and refractive surgery." C ombining femtosecond laser with intraoperative aberrometry results in a much higher percentage of eyes within 0.5 D of emmetropia than manual procedures, can virtually eliminate the need for ultrasound in all but the most dense of cataracts, and does not induce additional inflammation in the eye, according to three experts speaking on the topic at the 2013 American Academy of Ophthalmology meeting in New Orleans. Refractive target accuracy Over the years, published studies have verified the effectiveness of cataract surgery, but the literature shows only around 50% of eyes are within 0.5 D of predicted refractive targets (with ranges of 46%–55% within 0.5 D), said Bret L. Fisher, MD, medical director, Eye Center of North Florida, Panama City, Fla. Dr. Fisher's group wanted to determine the impact of intraoperative aberrometry on uncorrected visual acuity and predictability in femto laser cataract surgery, so they retrospectively reviewed consecutive cases that had cataract surgery with IOL implantation using the LenSx (Alcon, Fort Worth, Texas) without intraoperative wavefront aberrometry (Group 1). Group 2 comprised consecutive cases that had cataract surgery with IOL implantation using the LenSx with ORA intraoperative wavefront aberrometry (WaveTec Vision, Aliso Viejo, Calif.). Baseline demographics were fairly well matched between the two groups, and there were no statistically significant differences between the number of patients who received monofocal, multifocal, or toric lenses, he said. "This was really representative of the typical makeup of our patient population," he said. Evaluating eyes targeted solely for distance with the femtosecond laser, "about 90% of our patients were achieving the 20/40 benchmark, which was high," he said. Minimizing ultrasound energy Full fragmentation of the lens Source: Tim Schultz, MD, and H. Burkhard Dick, MD "About half achieved 20/25 uncorrected distance vision." In the group with both the femto and intraoperative aberrometry, 100% of the patients achieved 20/40 and about 73% achieved 20/25 UCVA, "and if we look at the benchmark statistic used to judge accuracy, about 80% were now achieving this level of accuracy as opposed to 50%–55% in the earlier studies," he said. Right before AAO, Dr. Fisher conducted a small study using the latest generation ORA technology, and had 88% of patients within 0.5 D, he said. "We're approaching 90% of our patients achieving refractive outcome accuracy with the newest technologies that we have available compared to the 50% or so we've been able to achieve in the past," he said, predicting those numbers will rise to even greater accuracy. Equally safe? Many say femtosecond-assisted laser cataract surgery is here to stay, but some naysayers question the safety of the laser itself. Femtosecond lasers have been commercialized for more than a decade, and the safety factor in refractive surgery is well known. A prospective, contralateral, randomized study enrolling 32–35 patients (the study is ongoing) with very strict inclusion and exclusion criteria was undertaken to try and address the safety component of the femto laser in cataract surgery, said Mike P. Holzer, MD, vice chairman and director of refractive surgery, Department of Ophthalmology, University of Heidelberg, Germany. "Suffice it to say, these were very healthy eyes aside from the cataract," he said. The group evaluated several postoperative and intraoperative parameters, including visual acuity, intraocular pressure (IOP), cell and flare, effective phaco time (EPT), capsulotomy, and centration, among others. "There was a difference between laser and manual procedures in EPT, which was much lower with the laser," Dr. Holzer said. "That's mainly due to the use of the laser to produce smaller fragments of the lens, so there is less phaco energy used." The precision of the laser is indisputable—with an intended diameter of 5.0 mm, the laser produced diameters of 5.03 mm, compared with the manual technique where the average diameter was 4.50 mm. "We were about 10% smaller than intended with our manual technique," he said. Otherwise, there were no statistically significant differences Phaco energy is a well-known cause of endothelial cell destruction, and reducing the effective phaco time with the femtosecond laser has shown promise. "We are very close to totally eliminating ultrasound from cataract surgery," said Tim Schultz, MD, Department of Ophthalmology, University Hospital Bochum, Germany. A study of their initial 650 cases treated with the Catalys femtosecond laser (Abbott Medical Optics, Santa Ana, Calif.) and the Stellaris phaco system (Bausch + Lomb, Rochester, N.Y.) showed that 90% of grade 2 cataracts (based on the Lens Opacities Classification System III scale), 66% of grade 3 cataracts, and 63% of grade 4 cataracts were able to be treated without ultrasound energy. The group changed some of the Stellaris settings as well as the phaco tip and individualized the grid size for every patient (200 to 500 microns), and were able to further decrease the amount of ultrasound needed. "In our last 400 cases, we were able to treat 99% without ultrasound energy. There were three cases that still needed phaco, all in the LOCS III group 4," he said. EW Editors' note: Dr. Fisher has financial interests with Alcon. Dr. Holzer has financial interests with Bausch + Lomb/Technolas. Dr. Schultz has no financial interests related to this article. Contact information Fisher: bfisher@eyecarenow.com Holzer: mike.holzer@med.uni-heidelberg.de Schultz: tim.schultz@kk-bochum.de