Eyeworld

EW CATARACT 34 June 2016 by Maxine Lipner EyeWorld Senior Contributing Writer Possible complications While the antibiotics themselves can be used safely, Dr. Mah finds that there are 2 types of toxicity that practitioners need to be on the lookout for—toxic anterior segment syndrome (TASS) and long-term toxicity. "It would be evident right away if you have an episode of TASS," Dr. Mah said. When it comes to long-term toxicity, however, there is no telling what may someday turn up. For example, Dr. Mah pointed out that the first reports with intracameral cefuroxime were made in 2001, with intracameral vancomycin being used in the 1990s. While there is some history, there is also the pos- sibility that something will happen 30 or 40 years down the line that was not foreseen, Dr. Mah pointed out, citing the occurrence of HORV. Because this appears to be a very rare event that occurs several weeks later, it was probably not associated with the use of the agent initially, Dr. Mah noted. "Likewise, we may find down the road that there is an increased incidence of macular degeneration or glaucoma that we didn't know about with intracamer- al antibiotics." Dr. Arshinoff pointed out that there's also an extremely rare chance of a reaction to Vigamox. He cited the recent case of a practitioner who used Vigamox for a vitrectomy, anisms of action as cefuroxime. So if the bug is resistant to cefuroxime, there is a good chance that it's also resistant to the usual treatment for endophthalmitis, Dr. Arshinoff explained. While the eye is imme- diately cultured, patients are put on routine endophthalmitis treat- ment before determining the exact cause. By the time more targeted medication can be used, it is usually too late with the highly aggressive Enterobacter bacterium. The same is not true with moxi- floxacin. While the endophthalmi- tis fail rates for moxifloxacin and cefuroxime are pretty much equiva- lent, Dr. Arshinoff pointed out there is a distinction. The difference is that moxifloxacin works on DNA gyrase and topoisomerase, which is a completely dissimilar mechanism from the agents used to treat en- dophthalmitis, he said, adding that both vancomycin and ceftazidime work instead by inhibiting bacterial cell wall synthesis. "When you have drugs that work by a totally differ- ent action, the chances of having cross-resistance is much lower," he said. As a result, if you are using moxifloxacin initially and this fails, when the patient is placed on tradi- tional endophthalmitis treatment, he or she will get better rapidly. "If you use cefuroxime, almost all the failed cases go blind," Dr. Arshinoff said. using it straight out of the bottle, there are no problems with dilution. Meanwhile, about 30 to 40% of practitioners rely on compounded moxifloxacin instead of Vigamox, he said. Some are using vancomycin intracamerally. "Historically, vanco- mycin was the 1 that kicked off ev- erything," Dr. Mah said, explaining that now, however, there are reports about a dramatic complication asso- ciated with intracameral vancomy- cin, known as hemorrhagic occlu- sive retinal vasculitis (HORV), which has been described as a delayed type 3 hypersensitivity reaction. This rare condition shows up anywhere from 1 to 4 weeks after the surgery. The typical cataract protocol in the U.S. calls for doing the second eye 2 weeks after the first, which means that there are bilateral cases. "It's a devastating vision loss," Dr. Mah said. "Most of these patients have worse than counting fingers vision." He views the use of vancomycin in the U.S. as a close third to cefurox- ime and moxifloxacin, but thinks that this may dissuade some from injecting it intracamerally. A fourth intracameral option is cefazolin. Reports out of Singapore show it has efficacy similar to cefu- roxime, Dr. Mah noted. With all of these intracamer- al agents, there are reports in the literature that they can be used safely; in terms of efficacy, there is the strongest evidence to support use of cefuroxime and moxifloxacin, he said. However, Dr. Arshinoff noted that there can be issues with cefu- roxime, which is an old drug. "Ce- furoxime is a drug that has known quite a lot of resistance," he said. There can be a particular problem in that some who are given intra- cameral cefuroxime may develop Enterobacter endophthalmitis, a bac- terium not sensitive to cefuroxime. Dr. Arshinoff said that patients often end up going blind because Enterobacter is also not usually sen- sitive to the drugs used to routinely treat endophthalmitis. "The reason is the drugs we use to treat en- dophthalmitis are vancomycin and ceftazidime," he said, adding that ceftazidime comes from the same class of drugs and both ceftazidime and vancomycin have similar mech- Opting for intracameral prophylaxis I t's 1 of the things that worries practitioners the most: cases of endophthalmitis following cataract surgery. To help keep this at bay, ophthalmologists have long relied on antibiotic drops. However, some are now turning to intracameral antibiotics. Currently, there are no antibiot- ics approved for intracameral use in the United States, according to Steve Arshinoff, MD, associate professor, Department of ophthalmology and Vision Sciences, University of Toron- to. But that hasn't stopped practi- tioners from using them off label, he noted. What's more, the evidence favors intracameral agents for en- dophthalmitis prevention. "Topical ones have never been shown to be effective," Dr. Arshinoff said. "Intra- cameral ones have all been shown to be very effective in studies that cumulatively have involved more than 1.5 million eyes to date." Francis Mah, MD, director of cornea and external disease, and co-director of refractive surgery, Scripps Clinic, La Jolla, California, likewise thinks that the use of in- tracameral antibiotics is preferable. "There is 1 study that was prospec- tive, and it was a head-to-head com- parison in cataract surgery compar- ing intracameral to topical agents," Dr. Mah said. When intracameral cefuroxime was given, there was a 4 to 5 times better outcome than with topical levofloxacin given perioper- ativately. 1 Intracameral agents Currently, there are several intra- cameral agents being used. These include cefuroxime, moxifloxacin, vancomycin, and cefazolin. In Europe, cefuroxime tends to be used the most, Dr. Mah noted, adding that some U.S. practitioners are also using this. "I think moxifloxacin is number 2 in terms of intracameral agents," he said. "I think about 60 to 70% of the intracameral moxiflox- acin used is commercially available Vigamox [Alcon, Fort Worth, Texas]. This is because Vigamox contains no preservatives. "People are diluting it or just using it straight out of the bottle," he said, adding that when Pharmaceutical focus Eye on endophthalmitis prevention To stave off endophthalmitis following cataract surgery, some practitioners are now administering antibiotics intracamerally during the procedure. Source: Francis Mah, MD

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