EyeWorld Asia-Pacific December 2011 Issue

December 2011 20 EW FEATURE frustration may never let you achieve it.” These patients “have always seen well otherwise. They require a lot of time and education—they don’t understand presbyopia or the compromise that would be required with current technology in order to give them near vision,” Dr. Koch said. Surgical considerations Dr. Weiss advised surgeons to consider the patient’s age and lens changes before deciding to offer a lens-based option—and to be prepared to spend a considerable amount of time in the pre-op phase educating patients. “If they’re +0.5 or +0.75 D and have already undergone a monovision contact lens trial, I’ll opt for monofocal lens surgery,” Dr. Harton said. The newer aspheric monofocal lenses, such as the Lenstec Softec HD (St. Petersburg, Fla., USA) or the STAAR Affinity and nanoFLEX aspheric lenses (Monrovia, Calif., USA), “tend to give patients a bigger depth of field, so we don’t have to make them –2 D in one eye just to give them great reading vision,” Dr. Harton said. The dilemma with any currently available lens is “we can’t predict who’s going to get the best accommodation out of it.” The “biggest change” in normal human accommodation is the change in the radius of curvature, he said. “With lens exchange, you’re removing the entire anterior capsule and taking away that engine. You might see a little bit of movement, but forward movement of the lens is not giving us the accommodation.” Cornea-based options “Absent a good accommodating IOL, I do not recommend any lens-based surgery,” Dr. Koch said. “On selected patients, I have done hyperopic LASIK or PRK in order to induce myopia and generate monovision. It works very well in patients who have already experienced monovision.” Limitations, of course, include some regression and potential retreatment “anywhere from 2 to 5 or even 8 years down the road as the eye changes and grows toward hyperopia,” he said. “If I have a young person whose lenses look fine and if the patient has some accommodation, presbyLASIK is a good option,” Dr. Weiss said. “For people in their early to mid-40s who are not reasonable candidates for lens- based procedures, I think it’s great. There will continue to be a niche for presbyLASIK for the foreseeable future.” Dr. Nichamin is more cautious, saying “a priori, I have a little bit of a problem etching a multifocal pattern on a cornea, but I’ve been wrong about other technologies more than I’ve been right.” Clear lensectomy “remains a little marginalized,” he added, but the corneal inlays in development “show promise and are really exciting.” Dr. Koch said the KAMRA (AcuFocus, Irvine, Calif., USA) is “a very intriguing option; it’s promising because it’s also removable.” Both the KAMRA and an inlay from ReVision Optics (Lake Forest, Calif., USA) have had “some good data” to date, he added. Another cornea-based procedure, the INTRACOR with the femtosecond laser (Technolas Perfect Vision, Munich, Germany) “uses femtosecond corneal treatments with a series of cylindrical cuts that cause a central steepening of the cornea,” Dr. Nichamin said. “Michael Holzer, MD, has presented data that’s reasonably promising. But there’s a narrow patient population that will initially be considered for INTRACOR.” Dr. Koch added presbyLASIK “might be a reasonable option, but I’ve not seen data on treating emmetropes.” He cited potential advantages as preserving some distance vision, “recognizing, of course, that there is going to be some contrast loss as you have with the intracorneal lenses.” He has concerns with any procedure— such as the INTRACOR—“that weakens the cornea to engender an effect.” Creating cylinders in the cornea to allow it to bulge forward a little bit centrally “makes me slightly uneasy,” he said. “Some superb people are doing it, both internationally and in the US, so I know their data is going to be reliable and helpful. Personally, I want to watch a little closer before I jump on board.” Dr. Weiss said the newer femtosecond lasers for cataract surgery “have the potential to be game changers in this area. We’re not there yet, but if we can produce routine caps and rarely go through posterior, we’ve decreased the risk again.” All the surgeons agreed, however, that their holy grail would be accommodating lenses that could consistently provide between 3.0 and 5.0 D or more of accommodation, could be implanted in safe procedures, and have minimal complications. Under the radar S ome companies that have not yet had people on the podium presenting, or had much published about earlier studies, are quietly moving ahead with their twist on a technology that will provide true accommodation. Here, a quick look at two of the companies (information gleaned from public websites and/or news items): AutoFocal IOL (Elenza, Roanoke, Va., USA) According to Dr. Koch, the lens works via photosensors. The IOL is battery-powered, with two lithium ion batteries that are rechargeable (patients wear a neck brace or a neck pad when sleeping or wear something over their eyes that would externally charge the batteries about once a week). The embedded sensors in the optics detect pupil size; the sensors are programmed to accommodate by detecting convergence in orientation. That, in turn, activates a liquid crystal that generates diffractive optics to create near vision. The company has said its “electro-active IOLs use a proprietary combination of liquid-crystal chemistry, electricity, and integrated- circuitry to create smart optics, which will provide patients with the ability to see more naturally and clearly over the full range of vision. The technology includes an electro-active switchable element that automatically adjusts focusing power electronically, in milliseconds, to maintain constant in-focus vision for various working needs and/or light environments. The lens is controlled by a micro-sized power-cell with an expected 50+ year rechargeable cycle life.” AkkoLens (AkkoLens, the Netherlands) AkkoLens has developed a novel accommodating intraocular lens that uses the ciliary muscle to move sliding aspheric surfaces laterally about 0.5 mm, yielding up to 5.00 D of accommodation, according to Michiel C. Rombach, MBA, chief executive officer of the company. The AkkoLens is “made from standard materials and easily positioned in the sulcus via simple and speedy, standard suture-free surgery; the lenses stay stably centered a small distance from the iris,” he said in an email to EyeWorld . Multicenter, international studies have shown “significant movement of the optical elements in blind eyes; multicenter trials of accommodation are continuing in seeing eyes.” Current trials are ongoing in Spain, Russia, and Belgium, Dr. Rombach added. Dr. Koch said the lenses “respond to ciliary muscle pressure by sliding over one another and increasing plus power, giving the patient the ability to read.” As the eye converges, the two optics will slide together to increase focus power, he said. Presbyopia - from page 18