Eyeworld

EW FEATURE 40 by Michelle Dalton EyeWorld Contributing Editor Intracorneal inlays showing positive outcomes While not yet on the U.S. 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 investiga- tion in the U.S. and are not yet ap- proved for marketing. Investigators for Revision Optics declined comment; in- formation 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 op- tions for presbyopia correction are LASIK (to create monovision), presby-LASIK, scleral segments, or premium IOLs. In the U.S., one other option—corneal inlays—is cur- rently being investigated. The inlays are typically inserted under a LASIK flap or in a corneal pocket, attempt- ing to improve near vision by creat- ing a central myopic area or increasing the depth of focus. Three devices are under investigation in the U.S.—the Flexivue Microlens (Presbia, Los Angeles), the Kamra (AcuFocus, Irvine, Calif.), and the Vue+ (Revision Optics, Lake Forest, Calif.). All three are more widely available outside the U.S.; each has a different mechanism of action and is implanted in the non-dominant eye. The Flexivue changes the cen- tral refractive index, the Kamra in- creases the depth of focus through the use of a pinhole, and the Vue+ reshapes the central cornea. "Corneal inlays are a break- through for presbyopia surgery in emmetropic presbyopes of the pre-cataract age," said Ioannis Pallikaris, M.D., director, Institute of Vision and Optics, University of Crete, Heraklion, Greece, and med- ical advisory board chair, Presbia. "The use of the femtosecond laser will help advance the use of these inlays and make the procedure eas- ier, 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 diame- ter, thin profile, and are highly per- meable, said Vance Thompson, M.D., director of refractive surgery, Sanford Health, Sioux Falls, S.D. "There's growing interest in corneal inlays because they blur dis- tance vision less than monovision laser and can be removed or ex- changed if the patient desires," he said during Cornea Day 2011, which preceded the ASCRS•ASOA Sympo- sium & Congress in San Diego. For instance, the Kamra inlay is 5 mi- crons thick, 3.8 mm in diameter, and has a 1.6 mm 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 pro- viding for approximately 2.5 D of accommodative effect while blurring distance vision less than monovi- sion 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, M.D., 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 creat- ing a corneal tunnel in the non- dominant eye, the device is placed about 280-300 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 dis- tance vision as would be expected with a classic monovision approach such as LASIK/PRK or monofocal lenses. I call this modified monovi- sion 'smart monovision' since it is dependent upon the pupil diame- ter." 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- 130 microns thick) in the non-domi- nant eye. The inlay creates a central steepening of about 2-3 mm, accord- ing to the literature. The inlay pro- vides 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 in- crease 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. February 2011 PRESBYOPIA June 2011 AT A GLANCE • Corneal inlays are under investiga- tion in the U.S., 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 treat- ment of presbyopia The Flexivue is virtually invisible under the slit lamp Source: Ioannis Pallikaris, M.D The Flexivue lens under retroillumination Source: Ioannis Pallikaris, M.D

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