Eyeworld

56 | EYEWORLD | SEPTEMBER 2023 C ORNEA by Liz Hillman Editorial Co-Director About the physicians Philip Dockery, MD, MPH Harvey and Bernice Jones Eye Institute University of Arkansas for Medical Sciences Little Rock, Arkansas Soosan Jacob, MD Director Dr. Agarwals Refractive & Cornea Foundation Dr. Agarwals Eye Hospital Chennai, India Aylin Kiliç, MD Medical Director and Founder Swiss Vision Group Istanbul, Turkey I ntracorneal ring segments (ICRS) were first introduced in the 1940s as a concept to treat myopia. 1 Fast forward to 2000 when they were proposed as a method to reduce corneal steepening in eyes with keratoco- nus. 2 In the 20+ years since, there have been several advances in the realm of intracorneal ring segments, both in terms of techniques and materials. EyeWorld spoke with Philip Dockery, MD, MPH, Soosan Jacob, MD, and Aylin Kiliç, MD, to discuss the latest in the world of intracorneal ring segments. "Intracorneal ring segments were first introduced as a way to treat low myopia before laser refractive surgery," Dr. Dockery said of their history. "But when the excimer laser was introduced in the mid-90s with PRK and LASIK, which were much more accurate ways to reduce myopia and regular astigmatism, intracorneal ring segments fell out of favor in that popula- tion. However, later around 2000, they started to become in favor for the treatment of kera- toconus, particularly mild, where the goal was to flatten the cornea and hopefully improve visual acuity. Intracorneal ring segments don't halt progression of disease, but the goal is to im- prove vision about 2 lines on the Snellen chart." Synthetic ring segments Synthetic segments and rings, such as INTACS (CorneaGen), Ferrara (AJL Oph- thalmic), MyoRing (Dioptex), and KeraRing (Mediphacos),* are generally used in conjunc- tion with crosslinking, which addresses progres- sive keratoconus, as a sequential procedure for improved visual acuity, whether that be with glasses, rigid gas permeable contact lenses, or uncorrected, Dr. Dockery said. Some of these, however, are described by the company as a treatment for progressive keratoconus. From a safety standpoint, Dr. Dockery said that synthetic intracorneal inlays are relatively safe, but literature documents some concern- ing safety issues, such as segment extrusion, secondary bacterial keratitis, neovascularization around the segments, and segment migration. Dr. Dockery was the co-author on a study that looked at intracorneal ring segments in eyes with advanced vs. mild keratoconus, finding that visual and topographic effects were greater in eyes with more advanced keratoconus, and there was no increased incidence of common complications in this patient population. 3 One of the challenges with synthetic seg- ments and rings, Dr. Jacob said, is the limitation with smaller optic zones. "ICRS were initially implanted at a larger optic zone, but soon it was understood that to get a better effect, there was a requirement to use smaller optic zones, so the optic zone in the case of INTACS shrunk from 6.8 to 6 mm. The KeraRing is available at a 5 mm optic zone. None of the synthetic ICRS go below this for obvious reasons. One is as we go centrally, the cornea becomes thinner, and we know that syn- thetic ICRS can lead to extrusions, melts, intru- sions, etc., and this is more common if there is not sufficient corneal tissue to cover the ICRS," Dr. Jacob explained. "In addition, even though greater effect may be obtained by implanting in even smaller optic zones, the probability of corneal melt as well as halos and glare are high enough that in optic zones smaller than 5 mm these are not used at all." Dr. Jacob said advancements in intracorneal ring segments include a decrease in diameter shape, a triangular shape (which helps go to the 5 mm optic zone, deflecting light away from the visual axis and preventing halos), different arc lengths (ranging from 90–120 degrees), and more asymmetric shapes with varying thicknesses. Allogenic ring segments The use of allogenic tissue was first introduced by Dr. Jacob in 2015 as CAIRS (corneal allogen- ic intrastromal ring segments), and it refers to intracorneal placement of fresh, unprocessed, processed, preserved, or packaged allogenic rings or segments of any type or length. 4 In the paper, Jacob et al. described using a dou- ble-bladed trephine on a donor cornea and implanting the tissue obtained into femtosec- ond laser-dissected corneal channels. This was followed by accelerated crosslinking. This pilot An update on intracorneal ring segments continued on page 58

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