EyeWorld Asia-Pacific March 2012 Issue

March 2012 24 EW FEATURE KAMRA corneal inlay: Pinpointing success near and far by Maxine Lipner Senior EyeWorld Contributing Editor AT A GLANCE • Internationally the KAMRA inlay has gained popularity • A new implantation system allows for centration within 1 micron • SIM-LASIK outcomes allow a wide range of presbyopic patients excellent distance and near acuity Corneal inlays for presbyopia gain momentum T he KAMRA corneal inlay (AcuFocus, Irvine, Calif., USA) is beginning to ride an international tide. Just 2 years ago patients in Japan who had received the KAMRA to help correct their presbyopia were practically non-existent, according to Minoru Tomita, MD, PhD , executive director, Shinagawa LASIK Center, Tokyo, Japan. Back then Dr. Tomita was performing just 30 to 50 cases per month. His monthly tally has since blossomed to more than 600. In Japan today approximately 4,000 cases with the KAMRA have been completed. Likewise in Europe, the technology is building a head of steam, finds Michael C. Knorz, MD , professor of ophthalmology, Heidelberg University, Manheim, Germany. He touts how well- received the procedure has been. “I practice in the most conservative country in Europe—Germans are always slow to accept new surgical techniques as they want long-term results,” he said. “Still I have had a lot of positive feedback, and the KAMRA is established as a routine technique in my practice.” Dr. Knorz finds that the device can be a particularly attractive adjunct to LASIK. “The KAMRA offers an option to correct presbyopia when combined with a well-established laser surgery— LASIK,” he said. While popular in pure presbyopes, the KAMRA is even more important for presbyopic myopes and hyperopes, he thinks. Dr. Tomita agreed that LASIK can be a powerful engine here. Dubbed SIM-LASIK, the procedure allows patients to seamlessly add near vision. “Usually we’re doing 12,000 LASIK procedures every month,” he said. When told they can get both distance and near, some happily pay the additional money, he finds. New challenges The inlay, which is generally implanted monocularly, relies on pinhole optics, according to Kevin L. Waltz, MD , Bloomington, Ind., USA. “What’s unique about that is that every eye doctor is very familiar with pinhole optics,” Dr. Waltz said. “But we’ve never surgically implanted pinhole optics.” Robert P. Rivera, MD , Salt Lake City, Utah, USA, who worked on U.S. FDA studies of the device, sees implantation of the KAMRA in the cornea as opening a new door for presbyopia correction. “It involves a new type of technology that hasn’t been applied to any great degree, and that is placing this implant within the layers of the corneal tissue for the treatment of presbyopia,” he said. Until recently one component that was a challenge with the KAMRA was centration. “This is actually quite important,” Dr. Rivera said. “The idea is that if you have a good system of centering the implant, the light rays going through the pinhole will be properly focused.” Dr. Waltz, who also worked on U.S. studies with the KAMRA, agrees that proper centration is critical. “We thought that there was a tolerance of about 500 microns, plus or minus, when we started the studies,” he said. “After we had been doing them, we went back and looked at centration versus acuity and we discovered that the tolerance is really 200 microns— that is difficult for a human to achieve without assistance.” The system now has a new implantation device, the AcuTarget system, which marks the proper placement position for the practitioner. “We measured and found that it was [accurate] within 1 micron,” Dr. Waltz said. Dr. Knorz described the AcuTarget system as comprised of two key components. The first is a measurement unit. “It takes a picture of the cornea and the adjacent conjunctiva and measures the axis of corneal astigmatism, the position of the pupil, and the position of the corneal reflex,” Dr. Knorz said. A second component allows the practitioner to visualize where to place the KAMRA inlay, with either an LCD monitor or a display built right into the operating room microscope. “The system is fed with the image taken with the first unit and it compares it to the actual image under the laser,” Dr. Knorz said. “It shows the actual position of the KAMRA inlay and the planned position.” Considering outcomes SIM-LASIK outcomes with the KAMRA inlay have been very promising. Dr. Tomita currently has data on 2,271 cases out to 16 months. Pre-op, these patients who also underwent SIM-LASIK had a mean visual acuity of 20/125 (6/38) and an uncorrected near acuity of J6. “Postoperatively uncorrected distance visual acuity becomes 20/20 [6/6] and uncorrected near vision is at J2,” he said. Dr. Knorz finds that the outcomes with the KAMRA itself, which is typically placed in one eye, surpass simple monovision at both distance and near. “At distance patients will see like a –0.5 D myope and not –1 D because of the pinhole effect,” he said. “The effective near add will be about –2 D.” Quality of vision with the KAMRA is slightly lower than in emmetropia but much better than in simple monovision with a target refraction of –1.25 D. “There is also a little bit of glare and halos at night due to light scatter, so patients have to be informed about this,” Dr. Knorz said. Dr. Rivera opted to have the KAMRA implanted in Japan and calls the experience phenomenal. “What led me to get the implant was seeing the clinical data,” he said. He found that as a surgeon who needs both good distance and near vision it made sense for him. Since then he has not needed reading glasses, although there has been a slight tradeoff. “In low light and dark conditions I do notice that there is a little bit of a halo effect and a little bit of glare compared to my other eye, but only in very low