Refractive Surgical Correction Of Presbyopia With The Kamra Corneal Inlay

By Alois K. Dexl, MD, MSc Within the past few decades, various surgical procedures for the treatment of presbyopia have been implemented in cataract and refractive surgery. Recently introduced into the market was the Kamra corneal inlay (AcuFocus, Inc., Irvine, California). This inlay has the Conformité Europpeéne (CE) Mark and is currently commercially available in the European Union and other markets around the world. The inlay is under investigation in US Food and Drug Administration (FDA) clinical trials for the treatment of near-plano and plano presbyopia; the study is fully enrolled, and 2-year follow-up data are now being collected. The annulus design (3.8 mm outer diameter and 1.6 mm inner diameter; Figure 1A) is intended to increase the depth of focus based on the principle of small-aperture optics to restore near and intermediate visual acuity with minimal impact on distance vision. The inlay is made of polyvinylidene fluoride, with nanoparticles of carbon incorporated that make the annulus opaque. Studies have supported the efficacy and safety of the prior-generation Kamra corneal inlay (ACI 7000) for the treatment of presbyopia with followups extending to 4 years.1 Within the past 3 years, AcuFocus has changed specifications of the inlay; the latest design is 5 μm thick and has more (and smaller) laser-drilled porosity holes than the previous inlay design. These 8,400 holes (diameter, 5 to 11 μm), arranged in a pseudorandomized pattern, allow sufficient nutritional flow through the inlay to sustain the viability of the anterior stromal lamella. The Kamra inlay can be implanted under a LASIK flap or in a femtosecond laser-created intrastromal pocket. In the clinical trial, the inlay was inserted primarily into a pocket via a temporal opening (Figure 1B). The inlay was then centered on the stromal bed using the microscope fixation light. A new intraoperative device, the AcuTarget System (AcuFocus, Inc.), will provide real-time centration guidance for the surgeon to ensure that the inlay is centered appropriately. Since 2006, we have implanted approximately 90 Kamra corneal inlays within clinical trials. More than 6,000 inlays have now been commercially implanted worldwide. In a recent clinical trial of 24 emmetropic, presbyopic patients implanted with the current Kamra inlay design, we found significant changes in reading performance parameters when evaluated with the Salzburg Reading Desk.2 After 12 months, the mean reading distance changed from 46.7 cm before implantation to 42.8 cm after, and the mean reading acuity at best distance improved from 0.33 logRAD to 0.24 logRAD, which is equivalent to the values achieved after bilateral implantation of diffractive multifocal IOLs and Intrastromal Corneal Inlays for the Treatment of Presbyopia