EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/357599
EW REFRACTIVE SURGERY 48 August 2014 by Ellen Stodola EyeWorld Staff Writer KAMRA inlay recommended for approval by FDA panel Three-year data is now available from the FDA trial of the inlay A Food and Drug Admin- istration (FDA) hearing was recently held for the KAMRA corneal inlay (AcuFocus, Irvine, Calif.) to review the inlay and provide premarket recommendations. At that hearing, the FDA Ophthalmic Devices Panel of the Medical Devices Advisory Committee voted in favor of recommending the KAMRA for approval. The KAMRA inlay has the CE mark in Europe and is seeking FDA approval in the U.S. Twelve-month, 24-month, and 36-month data have now been released. John Vukich, MD, Madison, Wis., and Jay Pepose, MD, PhD, Pepose Vision, Chesterfield, Mo., were involved with the trial, hear- ing, and other aspects of KAMRA data and commented on 36-month results of the inlay and what this means for its future. Dr. Vukich said the KAMRA inlay satisfies an unmet need for presbyopia treatment. "There are very limited options for individuals who want to be able to maintain their distance vision and recover the near that they have lost as a result of natural progression of presbyopia," he said. There are millions of people who would benefit from this type of technology, he said. "The KAMRA is particularly exciting as it doesn't diminish the distance acuity," Dr. Vukich said. This means that patients would not sacrifice part of their vision, as they might with monovision. How the inlay works "The KAMRA small aperture inlay works by isolating more focused central light onto the retina through its central 1.6 mm aperture, thereby narrowing the conoid of Sturm," Dr. Pepose said. The out of focus peripheral rays are blocked by the inlay itself, which extends depth of focus and improves both near and intermediate vision with minimal impact on distance vision. Best candidates Dr. Pepose said that the best patients to receive this inlay are between ages 45 and 65, with cycloplegic refrac- tion between plano and –0.75 D in the nondominant eye to be implant- ed with 0.75 D of astigmatism or less and close to plano in the dominant eye. They should have a corneal thickness of at least 500 µm and a corneal endothelial count of 2000/mm 2 . "Ideal patients have realistic expectations, minimal dry eye, and generally work or function in good lighting conditions," he said. Early concerns In early stages of the KAMRA trial and exploration into the device, there were a number of concerns with the inlay. "The initial inlay used to prove principle was made out of Dacron and was 25 µm thick, followed by a version made out of polyimide, which showed degradation with UV light," Dr. Pepose said. The inlay ma- terial was changed to a combination of polyvinylidene difluoride (PVDF) and nano-particles of carbon, which addressed the challenges presented by polyimide. Changes to the design of the original inlay reduced and ran- domized the pore pattern to help improve visual quality, and the thickness of the inlay was also reduced, which had less of an impact on topography. Dr. Pepose said that the inlay design of KAMRA represents a "decade of advancements and iter- ations." The earlier use of thin flaps or "flockets" and a thicker inlay re- sulted in a few cases of anterior flap thinning, he said. The commercial inlay (referred to as ACI7000PDT in published literature) is made of PVDF, is 5 µm thick, is 3.8 mm in diameter, has a 1.6 mm aperture, and allows 6.7% light transmis- sion. The inlay contains 8,400 laser-etched micro-perforations ranging in size from 5 µm to 11 µm to allow water, CO 2 /O 2 diffusion and nutrient flow. The pores are arranged in a pseudo-random pattern to minimize diffraction issues at night. Other important additions were the depth of the pocket of 180 µm or deeper and the use of 6x6 line-spot spacing or tighter with the femtosecond laser, Dr. Pepose said. Results Dr. Vukich said that the results with the KAMRA averaged almost 3 lines of improvement for the uncorrected near vision of patients. The 36-month report indicates that using pocket-based procedures have made results more predictable and stable. The mean UCDVA is 20/20, with acuity results staying consistent over time. Additionally, although there was a general BCDVA loss after the first week post surgery, this improved over time. Nearly all This simulation of enhanced depth of focus with a small aperture inlay is analogous to the effect of changing the f-stop on a camera. Note the impact of reducing a 4 mm aperture to a 1.6 mm aperture on depth of focus. Source (all): Jay S. Pepose, MD, PhD The KAMRA small aperture inlay is visible on slit lamp biomicroscopy, residing within a lamellar pocket.