EyeWorld Asia-Pacific December 2016 Issue

52 EWAP cornea December 2016 Patient with intracorneal ring segments Source: A. John Kanellopoulos, MD Intracorneal ring segment use remains controversial I ntracorneal ring segments (ICRS) have been available for more than 20 years as a means to correct myopia, and their use in the treatment of keratoconus spans almost as long. In the U.S., only Intacs corneal implants (Addition Technology, Lombard, Illinois; Oasis Medical, San Dimas, California) are approved; outside the U.S., in addition to Intacs, the Ferrara and Keraring (Mediphacos, Belo Horizonte, Brazil), Bisantis intrastromal segmented perioptic implants (Optikon, Rome), and MyoRing (Dioptex, Linz, Austria) are available. Intacs are hexagonal in geometry, the Kerarings are triangular, the Ferrara rings are used in a much smaller diameter and thus have a much higher efficacy, said A. John Kanellopoulos, MD , medical director, Laservision.gr Eye Institute, Athens, and clinical professor of ophthalmology, New York University Medical School. Another differentiating factor is size—the Kerarings have a smaller optical zone, whereas the Intacs are around 7 mm and the Intacs SK around 6 mm. Surgeons in the U.S. are beginning to use rings in conjunction with corneal collagen crosslinking for “patients who can’t get reasonable vision with a contact lens, yet aren’t bad enough to warrant a full corneal transplant,” said David Hardten, MD , Minnesota Eye Consultants, Minnetonka, Minnesota. There are two main goals in keratoconus, said Penny Asbell, MD , professor of ophthalmology, Icahn School of Medicine at Mount Sinai, New York: provide better vision, and stabilize the corneal shape. “Small optical zones will provide greater correction,” Dr. Asbell said, “but at the cost of increased and sometimes incapacitating glare.” Intacs “can provide improved best spectacle-corrected visual acuity, and perhaps an easier contact lens fitting,” in keratoconus patients, Dr. Asbell said. A potential benefit with ICRS is that they can be removed if issues develop, and then the cornea reverts back to baseline. When Dr. Kanellopoulos began using the rings in the late 1990s, “we were very pleased with the results using the rings horizontally and using a thicker ring inferiorly and a thinner or no ring superior to the cone, slightly decentered to ‘engulf’ the cone center. The visual results were immediate and remarkable, there was significant flattening of the cone and normalization of the posterior concaved surface of the cone, and very useful visual rehabilitation.” But there were complications including melts, extrusions, and even severe infections (one of which happened 15 years post Intacs surgery). Most patients complained of “significant glare from the rings themselves and from the white material accumulating at the banks of the rings,” Dr. Kanellopoulos said, but added many surgeons in Latin America, Asia, and the Middle East have reported significant success with the use of ICRS. Conceptually and biomechanically in the short term, Dr. Kanellopoulos said rings are “very effective” and “may be superior to using excimer laser normalization with topography- guided techniques (based on the Athens protocol introduced more than 10 years ago), especially when cones are decentered” in terms of changing both the anterior and posterior curvature of the cornea. It’s his clinical experience that the material (PMMA or rigid synthetic materials) “does not seem to be optimally compatible with the corneal collagen long term. More biomechanically and physiologically compatible materials such as crosslinked human allograph cornea ICRS-like inlays either within the cornea midperiphery or even within a stromal pocket may have a similar clinical effect with much less long- term morbidity.” Experience and the literature There is very little published on long-term data for ICRS. An issue of caution for clinicians is that if and when complications occur, the patient is usually a poor judge of how severe the complication may be—patients usually see well and have minor irritation on their corneal surfaces even when the segments are migrating and extruding, Dr. Kanellopoulos said. by Michelle Dalton EyeWorld Contributing Writer