EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/276058
E W FEATURE 110 by Maxine Lipner EyeWorld Senior Contributing Writer Operating on the laser's edge Femtosecond cataract outcomes B lade-free cataract surgery is on a lot of practition- ers' minds these days as practices begin to incor- porate the technology, akin to their refractive brethren a few years back with femtosecond LASIK. EyeWorld wondered about the effect on outcomes with femtosec- ond cataract surgery. From astigma- tism correction to effective lens position and beyond, here's what you can expect with femtosecond technology. Jack T. Holladay, MD, MSEE, FACS, professor of ophthalmology, Baylor College of Medicine, Hous- ton, said that the introduction of bladeless cataract surgery and that of femtosecond refractive surgery is very similar. "We always jump in and think, 'What is the actual scientific evidence for improve- ment?' and that's going to be related to the adoption by the doctors," Dr. Holladay said. "When the IntraLase [Abbott Medical Optics, Santa Ana, Calif.] first came out, the same ques- tions were raised in terms of com- paring the microkeratome to the femtosecond keratome." People wondered whether use of the femtosecond made a difference. Dr. Holladay said while there were some differences in femtosec- ond LASIK outcomes in terms of vi- sual acuity and contrast sensitivity, you would be hard-pressed to find a study showing this. "Yet in a period of two to three years, the femtosec- ond completely took over 90% of the market in terms of femtosecond LASIK," he observed. It was the dif- ference perceived by patients in the chance of having a catastrophic complication with mechanical mi- c rokeratomes that was the driving force with femtosecond LASIK, he explained. "People are afraid of blades. They don't like the idea of cutting," he said. "The laser is per- ceived as safer." The laser is safer and more precise, Dr. Holladay said. "With cataract surgery when the laser m akes the primary cataract incision, the secondary incision, the AK cut, everything that it does, the precision with which it does that is an order of magnitude 10 times better than a surgeon can do," he said. Creating and placing incisions with the laser in every case is always the same, he said. "It's never the same from one p atient to the next with the doctor." The pilot study with the Verion Image Guided System (Alcon, Fort Worth, Texas) did show a significant improvement in prediction error over manual cataract surgery and the Optiwave Refractive Analysis (WaveTec, Aliso Viejo, Calif.) intra- operative aberrometry. The study also showed that results with AK incisions were competitive with toric IOLs. Eric Donnenfeld, MD, clinical professor of ophthalmology, New York University Medical Center, New York, thinks that for astigma- tism correction, the femtosecond lasers add a level of predictability, reliability, and safety that can never be achieved with a manual limbal relaxing incision. "The fact that the majority of ophthalmologists never perform a manual limbal relaxing incision speaks to the point that many ophthalmologists are not comfortable with using a diamond knife to incise a cornea," Dr. Donnenfeld said. He said recent surveys show only about 25% of ophthalmologists currently do lim- bal relaxing incisions. "The arcuate incisions with the laser add a level of safety that can't be achieved manu- ally," he said. Dr. Donnenfeld said that several of the lasers have OCT visualization that show how deep the incisions go and significantly help to avoid perforations. "The incisions can be set at a specific depth and that's achieved," he said. George Stamatelatos, OD, senior clinical optometrist, New Vision Clinics, Melbourne, Australia, likewise pointed to this as a strength. "With the OCT that's available on the femtosecond lasers, you can get the precise depth that you want," Dr. Stamatelatos said. When you take an average thickness of the cornea in the peripheral zone, it is just an average, whereas with the femtosecond you know that you're going to go to 85% of the actual depth. Another advantage that Dr. Donnenfeld believes will take the femtosecond cataract approach into the mainstream is that it is con- trolled by the computer and doesn't rely on a certain skill level. "The novice surgeon can do just as well as the experienced surgeon," Dr. Donnenfeld said. The laser incisions are ad- justable after surgery, allowing out- comes to be titrated, Dr. Donnenfeld said. Akin to the intact serrations in a postage stamp, the incision can be put in place by the laser. The stamp isn't separated until these serrations are pulled apart. "I will make the incisions with a laser and then open these one incision at a time," he said. This almost eliminates the possibility of overcorrection and allows him to titrate the results to the desired effect. In addition, he said that the femtosecond allows for the possibility of creating intrastro- mal relaxing incisions that could never be done manually. Noel Alpins, MD, medical direc- tor, New Vision Clinics, also believes femtosecond lasers can be beneficial in correcting astigmatism. He cited a small series of LRIs that he did with the laser after first gaining access. "In about three out of 10 patients we did LRIs straight off the bat," Dr. Alpins said. "All of the patients had a good reduction of corneal astigma- tism, as well as refractive cylinder." In his view, the real benefit of using the femtosecond laser is that practitioners can precisely determine the depth of the incision. "You get exactly what you dial into the ma- chine," he said. Measurement obstacles He stressed, however, one variable people are not thinking about that needs to be considered is the white- to-white measurement. "If the white-to-white is 10 versus 12, then that incision can be anywhere be- tween 1 and 3 mm from the lim- bus," he explained. "You can have a lot of variability in the distance February 2011 Femtosecond phaco techniques March 2014 AT A GLANCE • Femtosecond incisions offer pre- cise depth and size unmatched by the manual approach, surgeons say. • Incisions can be titrated postop for more precise outcomes. • The jury is still out on whether or not effective lens position is improved in femtosecond cataract cases. The ASSORT femto LRI calculator allows planning of LRI procedures with well-known nomograms, together with postoperative astigmatism analysis using the Alpins Method. Source: Noel Alpins, MD continued on page 112 108-125 Feature_EW March 2014-DL2_Layout 1 3/6/14 3:59 PM Page 110