EyeWorld Asia-Pacific September 2011 Issue

43 EW CORNEA September 2011 Intracorneal inlays showing positive outcomes by Michelle Dalton EyeWorld Contributing Editor A Kamra corneal inlay implanted and recentered after 7 months Source: Günther Grabner, MD The Flexivue is virtually invisible under the slit lamp Source: Ioannis Pallikaris, MD AT A GLANCE • Corneal inlays are under investigation in the US, with promising results in the short term • Longer-term outcomes in Europe indicate the lenses provide improvement in near vision and little effect on distance vision • Inlays could become an alternative to monovision for the surgical treatment of presbyopia While not yet on the US market, clinical studies and longer-term outcomes in Europe indicate these have potential in treating presbyopia Editors’ note: This article discusses technologies that are under investigation in the US and are not yet approved for marketing. Investigators for Revision Optics declined comment; information on that inlay is derived from a literature/abstract search. A s the natural lens ages, its ability to accommodate begins to fail. The ability to return some of the near functions of our natural lens in its more youthful state—or some semblance thereof—is currently possible only through corneal or lenticular surgery. The options for presbyopia correction are LASIK (to create monovision), presby-LASIK, scleral segments, or premium IOLs. In the US, one other option—corneal inlays—is currently being investigated. The inlays are typically inserted under a LASIK flap or in a corneal pocket, attempting to improve near vision by creating a central myopic area or increasing the depth of focus. Three devices are under investigation in the US—the Flexivue Microlens (Presbia, Los Angeles, Calif., USA), the Kamra (AcuFocus, Irvine, Calif., USA), and the Vue+ (Revision Optics, Lake Forest, Calif., USA). All three are more widely available outside the US; each has a different mechanism of action and is implanted in the non-dominant eye. The Flexivue changes the central refractive index, the Kamra increases the depth of focus through the use of a pinhole, and the Vue+ reshapes the central cornea. “Corneal inlays are a breakthrough for presbyopia surgery in emmetropic presbyopes of the pre-cataract age,” said Ioannis Pallikaris, MD, director, Institute of Vision and Optics, University of Crete, Heraklion, Greece, and medical advisory board chair, Presbia. “The use of the femtosecond laser will help advance the use of these inlays and make the procedure easier, more customizable, and more predictable.” How they work “Synthetic keratophakia” was first described by José Barraquer in the 1940s; the concept has since evolved to products that have a small diameter, thin profile, and are highly permeable, said Vance Thompson, MD, director of refractive surgery, Sanford Health, Sioux Falls, SD, USA. “There’s growing interest in corneal inlays because they blur distance vision less than monovision laser and can be removed or exchanged if the patient desires,” he said during Cornea Day 2011, which preceded the ASCRS•ASOA Symposium & Congress in San Diego. For instance, the Kamra inlay is 5 microns thick, 3.8 mm in diameter, and has a 1.6mm opening in the center surrounded by 8,400 laser etched microperforations (to allow nutrient flow) randomized between 5 and 11 microns wide (to minimize optical side effects), Dr. Thompson said. He said that the 1.6 mm central opening creates a pinhole effect providing for approximately 2.5D of accommodative effect while blurring distance vision less than monovision laser. “Following the creation of a superior-hinged flap in the non-dominant eye, the Kamra inlay is centered on the stroma based on the first Purkinje reflex, at a minimum depth of about 170 microns,” said Günther Grabner, MD, director, University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. The Flexivue Microlens is 3 mm in diameter and about 15 microns thick, Dr. Pallikaris said. After creating a corneal tunnel in the non- dominant eye, the device is placed about 280 to 300 microns deep. “This is a ‘modified monovision’ technique,” he said. “It’s a procedure in the non- dominant eye to improve near vision, but with two specific characteristics. First, it’s reversible; second, it does not influence distance vision as would be expected with a classic monovision approach such as LASIK/PRK or monofocal lenses. I call this modified monovision ‘smart monovision’ since it is dependent upon the pupil diameter.” For instance, when the pupil size is greater (distance vision), the inlay’s effects are not as noticeable as when the pupil size is smaller (near vision). The Vue+ is a 2 mm diameter hydrogel inlay implanted under a modified corneal flap (about 120 to 130 microns thick) in the non- dominant eye. The inlay creates a central steepening of about 2 to 3 mm, according to the literature. The inlay provides a central near add zone and a paracentral intermediate zone for both near and intermediate vision, reports say. A few years ago, the inlay underwent alterations to increase its diameter from 1.5 mm to 2 mm; the smaller size led subjects to complain that image area was small. A cosmetic advantage is that the Vue+ index of refraction is the same as the cornea, rendering it virtually invisible post-op. Study outcomes During the 2011 ASCRS Annual Meeting, several surgeons presented results to date on the Kamra lens. Kevin L. Waltz, MD, Eye Surgeons of Indiana, Indianapolis, Ind., USA, reported on 407 patients with follow-up through month 6. In the non- dominant eye, 17.9% achieved continued on page 45