JAN 2012

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

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Page 32 of 71

Making light of corneal repair January 2012 by Maxine Lipner Senior EyeWorld Contributing Editor New method promises boost over suture use O cular surface defects are unfortunately par for the ophthalmic course. While traditionally repair of these has relied on su- tures, a new light-activated method for securing amniotic membrane to the cornea promises to make such repairs easier on patients and sur- geons alike, according to Min Yao, M.D., Ph.D., instructor, Harvard Medical School, Boston, and profes- sor, Jiao Tong University School of Medicine, Shanghai, China. Dubbed photo-chemical tissue bonding (PTB), results from a study published in the August 2011 issue of Lasers in Surgery and Medicine peg the process as superior to the use of sutures. The new light-activated method of repair makes use of two com- monly used ophthalmic aids—rose bengal staining and green light. It banks on an alteration in the rose bengal. "Rose bengal can be acti- vated by green light that can cause some electron change," Dr. Yao said. Due to this electron change, pro- teins will link to each other, as a re- sult of what investigators believe is covalent bonding. Then investiga- tors generate crosslinking of the tis- sue. "Because of this covalent bonding and the crosslinking, it will Overlooked continued from page 32 After excision, he recom- mended cutting dehydrated amni- otic membrane to the shape of the defect, using fibrin glue for adhe- sion, and placing the membrane over the wound. Post-op, his treatment regimen includes pred- nisolone acetate 1%, fluoro- quinolone, and topical NSAIDs. Treating SLK SLK can be associated with thyroid disease and is more predominant in the superior limbus, Dr. Hovanesian said. Obvious filaments can be asso- ciated with dry eye, leading to an underdiagnosis of SLK, Dr. Palmon said. "Patients can also experience times of flares, where they're very symptomatic, but then the SLK can calm down and be more comfort- able," Dr. Palmon said. If the flare cause the tissue to stick to each other," Dr. Yao said. Dr. Yao sees several reasons to consider the method. "The cornea is delicate tissue and it is difficult to suture it," she said. Also, although the cornea should be transparent, no matter how fine the sutures, it will cause some scarring and angiogene- sis. "That's why we came up with this idea to use PTB to seal the cornea, like a transparent Band-Aid on top of the wounded cornea," Dr. Yao said. Under a laboratory spotlight To study whether this would work, investigators generated small defects in 40 rabbit corneas. They then placed human amniotic membrane on top of the defect of the cornea. In one group they applied rose ben- gal on top of the membrane and then irradiated the area for 10 sec- onds with green light. Investigators used 0.4 watts per-centimeter- squared of the irradiance, which was applied for 200 seconds. "That gen- erated very nice bonding," Dr. Yao said. Meanwhile, traditional 8-0 vicryl sutures were used in the con- trol group. "After the surgery, the next day we found that in the con- trol group the rabbits were not happy because I believe that even if the suture was very fine, it was still a little uncomfortable for them," Dr. Yao said. "However, with the PTB site, there was no irritation like from the sutures." When investigators checked the angiogenesis on the new cornea, they found that by day 14 there were significantly fewer new blood vessels in the eyes where PTB was used compared to sutures, and there were also significantly fewer inflam- matory cells. By the 4-week mark there was much less granulation tis- sue formation associated with scar formation in eyes that underwent PTB versus suture use. "This suggests that PTB has better results because it has less blood vessel formation, less inflammation, and less scarring," Dr. Yao said. So it seems to offer better vision compared to the sutures with PTB, she believes. So far no complications have occurred with this method. Dr. Yao stressed that it is quite simple and uses materials commonly found in ophthalmic practices. "We used this with rose bengal strips, which have been in use in the clinic already," Dr. Yao said. "Green light is also ap- proved for eye treatment already." An illuminating shift Dr. Yao thinks that the method could result in a significant change for ophthalmologists. "The potential for PTB use for the cornea is plenty because there are a variety of advan- tages," she said. This could be used to bond just about anything to the cornea. Dr. Yao sees it as natural for corneal transplantation, as well as for diseases or injuries that cause oc- ular surface defects. The PTB process has inherent advantages that Dr. Yao thinks give it a natural leg up over the use of sutures for adhering grafts to the cornea. "Almost every surgeon can do this process, unlike sutures, which require surgical skill," Dr. Yao said. Also, the time required for the process, which has actually been shortened since the study, is consid- erably less. "If we use the newer irra- diance it should take about 150 seconds," she said. "Sutures will take a much longer time." Overall, Dr. Yao sees the future for the technique as promising. "We're looking forward to using this in the clinic," she said. "So far we haven't found any safety issues that cause concern from this method." EW Editors' note: Dr. Yao has no financial interests related to this article. Contact information Yao: 86-31-35321016, yao.min@mgh.harvard.edu EW CORNEA 33 occurs when patients are first begin- ning a dry eye treatment and then regresses, it's likely the physician and patients will attribute the relief to the new drops, he said. "They may end up OK for weeks or months before another flare-up occurs," he said. "That's usually when I start seeing patients—after they've had several flare-ups and the dry eye treatment has not been suc- cessful." Dr. Palmon advised treating SLK medically first, usually aggressively treating the dry eye component with topical cyclosporine 0.05%, ar- tificial tears, and/or punctal plugs. "If there are filaments, I'll put them on Mucomyst (acetylcysteine, Bristol-Myers Squibb, New York) 10% twice a day," he said, because the drug dissolves the mucus attach- ments common with SLK. He'll also prescribe topical mild steroids, such as Lotemax (loteprednol etabonate ophthalmic suspension, Bausch + Lomb, B+L, Rochester, N.Y.) until symptoms quiet down. "If the conjunctiva is not too thickened and stretched out, pa- tients can be comfortable with ag- gressively treating the dry eye component," he said. If bandage contact lenses also fail to provide comfort, surgeons can remove the thickened conjunc- tiva superiorly and use amniotic membrane as well as fibrin glue to help prevent scarring, "but I think that should be a last resort," Dr. Palmon said. "Most patients, when medically treated aggressively, will quiet down and most of the flare- ups can be managed without per- forming resection." If patients are being treated sur- gically, however, "you have to re- mind them surgical treatment is not the only management—if the Schirmer's scores are still low, they will continue to need aggressive dry eye treatment," Dr. Palmon said. Drs. Palmon and Hovanesian advised treating either condition medically before surgically. EW Editors' note: Dr. Hovanesian has fi- nancial interests with Allergan (Irvine, Calif.), B+L, and IOP Ophthalmics (Costa Mesa, Calif.). Dr. Palmon has no financial interests related to this article. Contact information Hovanesian: 949-951-2020, johnhova@gmail.com Palmon: 239-768-0006, rpalmon@swfleye.com

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