EyeWorld Asia-Pacific December 2016 Issue

EWAP CORNEA 53 December 2016 “Sometimes even if a patient gets better vision, he may be unhappy because of increased glare,” Dr. Asbell said. “For these relatively rare patients, we are caught between a rock and a hard place—as clinicians, we want to correct the vision, but we don’t want to induce so much glare the patient is even more unhappy.” There are many publications on Intacs safety and efficacy, but there are still unanswered questions, such as the stability of the cornea over years post-ring replacement, Dr. Asbell noted. Dr. Kanellopoulos, said the lack of large, longitudinal studies on the long-term safety and efficacy of the rings creates a disservice for the current techniques and technologies. “There is no good comparison data in the literature, and there is no long-term data in the literature. It appears that Kerarings may be the leader of the pack at this point as far as their efficacy,” Dr. Kanellopoulos said. Because results are “quite unpredictable, and long- term stability and safety is questionable,” Dr. Kanellopoulos has abandoned using these devices altogether. “I admit though that their initial visual results are sometimes remarkable and may be better when compared to what we have been doing as an alternative for more than 10 years now, which is a combined partial topography- guided PRK and high fluence CXL (the Athens protocol). Predictable and long-term visual rehabilitation and stability has proven in our hands to be far better in the Athens protocol patients,” he said. Dr. Asbell noted that few surgical procedures have a lower risk profile. With Intacs, no tissue is removed, the surgery is done outside the optical zone, and the rings can be removed. PRK and CXL have a higher potential for poor healing leading to scarring and permanent loss of vision, although these complications are rare. Using femto Dr. Hardten prefers using a femtosecond laser to create the channel, as “the accuracy and depth are more consistent,” he said. “In cones that are off-center, I use a 0.45-mm segment in the steeper area, and a 0.21-mm segment in the opposite meridian. I center the larger Intacs at the apex of the cone based on posterior elevation on the Pentacam [Oculus, Wetzlar, Germany]. I do conductive keratoplasty outside of the segment before creating the channel.” Dr. Asbell remains unconvinced about the superiority of femto techniques, finding outcomes to be “pretty similar” between the femto and manual techniques, but said using the femtosecond laser is substantially easier than creating the channel manually. Patient cost may be higher with pass-along facility fees, but there’s less discomfort, too, she said. She also advocates using the ring manufacturer’s supplied nomogram, which will evaluate how steep the cornea is, the amount of astigmatism, and whether the cone location is more central or peripheral, and prefers to make her incisions on the steepest meridian of the cornea. Dr. Kanellopoulos has used a femto laser for more than a decade as an alternative to ICRS implantation, and has found its use to provide much more accurate positioning than manual channel creation. He prefers not to remove any epithelium and to use a suture “for a few days at the incision site.” He implants the rings away from the incision site “so there is no mechanical stretching of the incision site or melting.” Patient followup Post-implantation, patients “need to be seen a little bit more often in the early postop period because intrastromal corneal rings are made out of plastic, it’s clearly a foreign body, and as with any implant, there’s a higher risk of infection,” Dr. Asbell said. She recommends close followup during the first 2 postop weeks to ensure the channel remains infection-free. If infection does develop and does not respond to topical antibiotics, the devices can be removed and an antibiotic course continued. Dr. Hardten uses a 10-0 vicryl suture in the incision and also in between the segments 180 degrees away from the incision. “This dissolves in 6 weeks. Usually the patient can go back into a contact lens at 4 to 6 weeks or after the suture dissolves,” he said. “I do transepithelial crosslinking, so the epithelium is usually stable by then.” Dr. Kanellopoulos recommended “very careful followup at least every 6 months” because of the potential for late- occurring complications. Rings have been shown to “work best in corneas that are thicker than 400 microns, and their need is usually more necessary in corneas that have dropped under 400 microns, and there the options are very limited,” he said. He “would use them today only for a patient who desires an immediate refractive result, but in the long-term I would advise patients to have the rings removed and to choose some type of crosslinking procedure that appears to be better tested and stable.” Until crosslinking is covered by insurance in the U.S., Dr. Asbell thinks that may tip the scales in favor of ICRS for now, but she expects combination treatments will become more prevalent in the future. “Rings are here to stay, and I think they have a role,” she said. “They’re minimally invasive. Crosslinking with epi-off techniques can result in infections, scarring, or permanent loss of vision. In my mind, there’s no clear picture of which procedure provides better vision or stability.” The combined use of ICRS and crosslinking “will continue to be a major treatment for keratoconus and ectasia,” Dr. Hardten said. EWAP Editors’ note: Dr. Asbell has financial interests with Addition Technology. Drs. Hardten and Kanellopoulos have no financial interests related to their comments. Contact information Asbell : penny.asbell@mssm.edu Hardten : drhardten@mneye.com Kanellopoulos : ajkmd@mac.com