EyeWorld Asia-Pacific September 2013 Issue

53 EWAP rEfrActivE September 2013 Patrick VERSACE, MD Vision Eye Institute 2/75 Grafton ST Bondi Junction 2022, Australia Tel. no. +61-2-93863666 patrick.versace@bigpond.com C orneal inlays are an attractive concept as an additive corneal procedure for the correction of refractive error. Much effort, attention and excitement surrounds their application to presbyopia correction. KAMRA and Presbia inlays are fully registered and commercially available in a number of countries including Australia. Raindrop has received CE mark. KAMRA is optically novel, being a small aperture inlay that increases depth of focus through the pinhole effect. It is a dark annulus with a central clear aperture implanted into the nondominant eye. This works well for many patients and gives functional near vision with almost no impact on distance vision. Surprisingly, patients do not notice the reduced light entering the inlaid eye. Early trials with the KAMRA, while demonstrating its ability to give near vision, had problems with compromise of the overlying cornea and it was quickly realized that the device needed to be implanted deeper in the corneal stroma. It is now either implanted under a 200-micron thick flap or in a 200-micron deep corneal pocket (created with the femtosecond laser). Refractive instability remains a challenge with the KAMRA inlay and steroid responsive corneal inflammation can lead to hyperopic shift with loss of near vision up to 18 months after inlay surgery. For all corneal inlays, centration is critical to success. AcuFocus has worked with SMI to develop a system to facilitate this but it has had limited clinical success and we continue to rely upon manual techniques to align the inlay with the visual axis using the first Purkinje reflex. In practice this is a rapidly acquired skill though recentration of the inlay will sometimes be required. Presbia works both as a refractive lenticule (with choice of near add of 1.5 to 3.5D) and through induction of spherical aberration to give near add power and increased depth of focus. It is a clear hydrophilic polymer lenticule with no central power and a ring of plus power implanted in the nondominant eye in a 300-micron deep corneal pocket. Presbia is an appealing inlay as the near add power is chosen to match the patients age and it is a truly reversible procedure. Presbia has an advantage in being invisible and having minimal impact on corneal stability. As a hydrophilic material implanted deep in the stroma, it should not compromise the nutrition of the superficial cornea. Patients achieve good near vision BUT there is a loss of several lines of UCDVA and often some temporary (months) loss of BCDVA. Raindrop is a hydrogel inlay placed at 120-microns depth in the nondominant eye. It works by altering the corneal surface shape to make it more prolate (inducing spherical aberration) to give increased depth of focus. Phase 3 FDA trials are underway. I share the article’s enthusiasm for corneal inlays for the correction of presbyopia—particularly for the emmetropic presbyope. As an additive, reversible corneal procedure utilizing a corneal pocket technique we have a surgical approach with great versatility. Each of the inlays, however, has significant potential compromise at present and we will see further refinements of both inlay materials and optical properties before this approach is more widely adopted. Editors’ note: Dr. Versace is a consultant for Carl Zeiss Meditec (Jena, Germany) but has no financial interests related to his comments. if it’s been years since the first flap was made.” The devices also have the potential to extend the LASIK market for people who are in their late 40s or early 50s, he said. In the Netherlands, Dr. Verdoorn creates a 150-micron, 8-mm flap with a 150-kHz femtosecond laser, and suggests surgeons ensure the flap is well centered before proceeding, especially in hyperopes. “These need to be in the best position possible to get the best possible vision,” Dr. Whitman said. “If the inlay is not positioned properly, it might affect distance vision.” He has yet to have that happen in any of his patients, but did note the possibility. Learning curves These devices have short learning curves, Dr. Waring said. “Any corneal refractive surgeon can pick it up very quickly,” he said. “Using an advanced femtosecond laser is important for the pocket or flap. Centration is important, too—inlays are forgiving enough that patients will do well as long as the inlays are generally placed correctly. And, of course, patient selection is critical. We recommend healthy eyes—you really want to optimize the ocular surface.” The KAMRA can be “easier to see during the day if the light hits it right,” Dr. Whitman said. “Other inlays are transparent. That may be an issue for some people.” The KAMRA works by small aperture optics (basically a pinhole in the center of the pupil), Dr. Hovanesian said. “It does reduce light entering the eye, but it doesn’t seem to be clinically problematic for patients or cause difficulty with nighttime glare or contrast.” Dr. Whitman said the Raindrop allows surgeons to go about 150 microns deep, whereas the others need the inlay placed about 200 microns deep, “which we normally wouldn’t be comfortable doing with LASIK.” He describes the implantation technique as simply lifting the flap, looking under the microscope, and placing the inlay “as best you can” over the center of the pupil. “The continued on page 56