NOV 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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44 EW FEATURE Corneal crosslinking November 2013 Peak continued from page 43 Ferrara Ring on the right and Intacs on the left in the same cornea. The prismatic effect of the Ferrara reflects light back unlike the Intacs segment where there is no reflection. have a lot of astigmatism," he said. "Then I will put intracorneal ring segments in." For this he prefers the Ferrara Ring. "I use these very shortarc rings—they're 90 degrees," he said. "They're superb for correcting astigmatism." At the time of surgery using intraoperative keratoscopy, he rotates the ring into the position where it reduces astigmatism most, a technique that he learned from Jose F. Alfonso, MD. If necessary he puts in a second ring segment to decrease the astigmatism further. "So I know on the table that I've reduced astigmatism," Dr. Daya said. He finds these ring segments preferable to Intacs, explaining that because Intacs have big, wide arcs, they're mostly useful for flattening the cornea, but only reduce the astigmatism a bit. "The Ferrara Rings are great because they have a short arc," he said, adding, "They're not so wide so you're confining the effect in a small area, so it's much better for astigmatism." Still, Dr. Daya has over the years put in approximately 150 Intacs in keratoconus cases. While he finds these are able to flatten the cornea considerably, in his view outcomes are marginal. "Patients never see brilliantly," he said. "You can get them back into a contact lens or a piggyback system with a soft lens and a hard lens on top, but it's often not satisfactory." About two-thirds of patients overall in his experience benefited from intracorneal ring segments such as Intacs or the Ferrara Ring. "We found that it was the ones with milder disease who did well," he said. In the more advanced cases treated with these, however, the patients eventually opted to have a corneal transplant. "Then they turned around and asked, 'Why didn't you do this in the first place?'" Dr. Daya said. This has caused him to revise his opinion somewhat in cases of advanced bilateral keratoconus. "I will probably do a graft earlier in one eye and deal with the other eye at another time or put an Intacs in," he said. Topographic-guided PRK Simon P. Holland, MD, clinical professor, University of British Columbia, Vancouver, together with David TC Lin, MD, finds another adjunctive option to crosslinking to be superior to intracorneal ring segments—the use of topographicguided PRK. With this technique, topography is used in conjunction with the excimer laser to help improve the regularity of the corneal surface. "The big advantage is that it reduces the irregular astigmatism and the options open up for satisfactory soft contact lens wear or glasses, whereas those were precluded prior to the surgery because of the severe irregular astigmatism," Dr. Holland said. In the last five years Drs. Holland and Lin have performed more than 400 topographic-guided PRK procedures, currently with sufficient follow-up to report on 165 cases. "At one year, we have 49% 90-degree Ferrara in this patient three months earlier reduced the astigmatism and coma. The intraoperative image is of a toric AT Torbi implant in place following cataract surgery. The patient's vision postoperatively was 20/25 unaided. Source: Sheraz Daya, MD getting 20/40 or better uncorrected vision," he said, adding, "We get about half of them to 20/40 uncorrected and that's across the range from mild to severe keratoconus." He finds that probably about a quarter gain two lines or more of best corrected acuity. The topographic PRK ablation is done in the same sitting as the crosslinking procedure. "We would do the PTK/topographic PRK first and then do the crosslinking," he said, noting this way the tissue removed has not yet been crosslinked. Dr. Holland said that he considers some refractive treatment whenever possible. Even in those cases where the patient is under 18 or has a thin cornea that precludes use of the topographic-guided approach, he generally performs some PTK. "We can take advantage of the fact that the epithelium is going to be thinner over the steeper areas of the cornea," he said. "You do get minimal blunting of the cone doing the PTK, which we use for epithelial removal (for crosslinking) as well." In Dr. Ku's view, PTK with crosslinking may be a viable option for those who don't have the expensive equipment or software needed for topographic-guided PRK. This traditionally treats about 50 microns and can help to regularize the central cornea. The approach, she noted, was first promoted by Doyle Stulting, MD, to remove subepithelial scars in keratoconus patients. A study published by the Kymionis group showed benefit to using PTK in conjunction with crosslinking. "They found that 50 microns of transepithelial PTK during crosslinking resulted in better visual and refractive outcomes compared to mechanical epithelial removal," Dr. Ku said. A study conducted by a group Dr. Ku worked with in Toronto, published in the August issue of the Journal of Cataract & Refractive Surgery, showed promise for PTK combined with same-day Intacs and crosslinking. "At six months we showed significant improvement in uncorrected and corrected distance visual acuity as well as mean and steep keratometry," she said. "No one lost best corrected vision." Although a larger study with longer follow-up data is needed, Dr. Ku views this as a viable adjunct in selective patients. Overall, Dr. Holland pointed out that crosslinking together with adjunctive treatments where needed has the promise long term of reducing the need for surgery in keratoconus. "I think it's rapidly evolving," he said. "What we say now and what we do now is probably going to be very different one year from now." EW Editors' note: The physicians have no financial interests related to this article. Contact information Daya: sdaya@centreforsight.com Holland: Simon_holland@telus.net Ku: judyku1@yahoo.co.nz

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