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EW NEWS & OPINION 24 October 2017 Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer that the infection had not recurred, and the patient had not experienced any adverse reactions. After just a few weeks, the patient's endotheli- um was normal. "About 9 months after infection was resolved, I did cataract surgery on her and her cor- neal endothelial function is doing very well," Dr. Amescua said. "So far, we haven't seen significant side ef- fects or toxicity, but we are studying this in rabbits currently." Investigators theorized that at the heart of this treatment is a chemical reaction. "The fungus eats the rose bengal, and the single oxygen released by the chemical reaction kills the organism," Dr. Amescua said. "That's our hypoth- esis—that we're creating a toxic reaction that may be affecting DNA replication with the nucleus of the fungal organisms." This hypothesis still needs confirmation. Photody- namic therapy may also be making the corneas more resistant to enzy- matic degradation and giving time for the medications to kill the organ- isms before the cornea perforates. Dr. Amescua is optimistic about the treatment's potential. "It could be huge because it's not expensive," he said, adding that all you need is a light source and a chemical that costs about $0.45. It should be easy to offer patients with poor access to medications as well as those who are not responding well to the current standard antibiotic regimen, he said. said. "If you excite rose bengal with a green light, you create another photochemical reaction, and this was very successful for killing all types of fungus in the lab." In one study, investigators demonstrated a 100% kill rate in the lab of common isolates such as Fusarium, Aspergillus, and Candida, Dr. Amescua noted. 2 In another study, investigators determined that rose bengal therapy was likewise effective against two methicillin-re- sistant Staphylococcus aureus keratitis strains. 3 When faced with the patient who had multi-drug resistant Fusarium keratoplasticum keratitis, rose bengal seemed a viable option. "She developed this ulcer and after undergoing treatment with every- thing possible, she was desperate," Dr. Amescua said. When investi- gators took a sample of the ulcer, they found this was Fusarium. "We treated it first in the lab and got 100% kill," he said, adding that they felt comfortable recommending the unique light treatment with rose bengal to the patient, who agreed to try the option. After getting approval from the hospital, they proceeded with the treatment. The patient underwent two treatments with the rose bengal 0.1% agent in conjunction with exposure to green light. "She did very well," Dr. Amescua said. At the 8-month mark, investigators found use of corneal crosslinking. "In some parts of the world, there are reports of using UV light and riboflavin as a possible treatment for infectious cor- neal ulcers because UV light is used in other fields of medicine to treat infections like in the skin," he said. The idea was that the crosslink- ing approach, more correctly termed a photodynamic reaction, could be a possible treatment for corneal infections. "The UV light with the riboflavin creates a chemical reac- tion that releases a single oxygen, and this is toxic for the microorgan- isms," Dr. Amescua said, adding that it also makes the cornea stiffer and more resistant to enzymes degrad- ing the cornea, and the hypothesis is that this will decrease chances of corneal perforations. However, while practitioners were able to kill many types of bacteria isolated from patients with this technique, they were unsuccessful in killing fungus or parasites. "Those two are the most aggressive infections that we see in the cornea," Dr. Amescua said. "We also have negative results trying to kill fungi in vitro." After determining that the pho- todynamic reaction of UV light and riboflavin didn't work in their hands for treating the more aggressive organisms, they started looking for different photodynamic agents, and rose bengal was one of these. "Rose bengal has been used in ophthal- mology for 50 years," Dr. Amescua Unique photodynamic approach can combat aggressive infection F aced with a desperate patient with multi-drug re- sistant Fusarium keratoplasti- cum keratitis in whom none of the traditional treatments seemed to work, practitioners at Bascom Palmer Eye Institute took a different approach, according to Guillermo Amescua, MD, assistant professor of clinical ophthalmology, Bascom Palmer Eye Institute, Miami. They turned to a technique in their armamentarium that they had under study: use of rose bengal photody- namic antimicrobial therapy. Inves- tigators detailed how the patient responded to this unique approach in a recent issue of Cornea. 1 "We don't have many topical antifungal treatment options for infectious keratitis, and most of the medications we currently have do not have good penetration to the deep corneal tissue. We're also starting to deal with more resis- tant organisms," Dr. Amescua said, adding that they deal with a lot of advanced infections at the large corneal referral center at which he works. With that in mind, prior to studying rose bengal photodynamic antimicrobial therapy, Dr. Amescua had been looking into another tech- nique for handling infections: the New treatment for corneal ulcers The patient is a 72-year-old female referred with active ocular cicatricial pemphigoid (OCP) that was not systemically treated and lead to trichiasis and chronic keratitis. The last episode of keratitis became infected with culture proven Curvularia keratitis. The patient was referred after 1 month of topical and systemic antifungal treatment and worsening on clinical exam. To start systemic immunosuppression to control her OCP condition, we needed to cure the fungal keratitis immediately and avoid a corneal perforation. Source: Guillermo Amescua, MD continued on page 26

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