Intracameral antibiotics prophylaxis

Pros and cons of intracameral antibiotics highlighted in debate.

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Steve Arshinoff MD
There is still no broad consensus on the safety, efficacy and necessity of intracameral antibiotics (ICA) to prevent postoperative endophthalmitis,delegates attending the World Ophthalmology Congress in Barcelona were told. In a special session devoted to controversies in cataract surgery, Steve Arshinoff MD, FRCSC, presented the case for routine prophylaxis with ICA while Andrzej Grzybowski MD, PhD, argued against. Dr Arshinoff said that he routinely uses intracameral moxifloxacin in all his unilateral and bilateral cataract surgeries, and that he based this decision on the weight of published evidence in the scientific literature. “While it became popular to use intracameral antibiotics after the ESCRS study in 2006, it was actually studies by Gimbel and Gills in the early 1990s that gave us the first conclusive evidence that this approach works. There have been many more studies since, totalling about 6 to 7 million eyes, all of which show about an 80% reduction of infection irrespective of the starting point in endophthalmitis rates,” he said. Dr Arshinoff’s own study of the use of ICA in immediate sequential bilateral cataract surgery in 125,000 eyes echoed the results in the scientific literature. “Without antibiotics the infection rate was about one in every 2,000 cases whereas when intracameral cefuroxime was used the rate fell to one in every 9,175 cases. The infection rates with intracameral vancomycin or moxifloxacin were still lower, making the overall rate using intracameral antibiotics one in 16,800 cases,” he said. Dr Arshinoff noted that a review by Per Montan MD found 24 studies encompassing about 6 million surgeries showing about an 80% reduction of endophthalmitis infection rates with ICA. “There were two studies of about 90,000 surgeries that showed no benefit, but I reviewed those two papers and both used too low a dose of intracameral antibiotic for it to be effective. If you don’t put enough in the eye, you don’t get much effect,” he said. In terms of the best intracameral antibiotic to use, Dr Arshinoff said that studies by Libre et al. in 2017 and Bowen et al. in 2018 indicate that moxifloxacin appears to be the safest and most effective for endophthalmitis prophylaxis, but appropriate dosing is key. “Vancomycin and cefuroxime are less effective than moxifloxacin due to injected dose over minimal inhibitory concentrations (MIC) ratios not being as good, and also time dependence, which means that they need to be in the anterior chamber for much longer. However, no matter what drug we use the infection rate will never go to zero and we can always do better and we find new ways to make things safer,” he said. LACK OF EVIDENCE Presenting the case against routine ICA use, Dr Grzybowski said that many surgeons have still not adopted the practice because of a lack of clear evidence from randomised, trials as well as potential risks from compounding or mixing antibiotic solutions when no approved formulations are commercially available in some countries. For many years it was believed that Vancomycin IC is safe – today it is known that it might lead in some cases to retinal vasculitis (HORV) and a very poor outcome. Cefuroxime, propagated by ESCRS as the best IC antibiotic in last 10 years, is known not to cover certain important bacteria, i.e. Enterococcus sp., and because of that in Sweden the practice of supplementing it with ampicillin in some cases was started. Moxifloxacin is very commonly used in general medicine and in ophthalmology, what might soon lead to increase in bacterial resistance and loss of its activity to many microorganisms. “The reality is that there is no perfect intracameral antibiotic available at the moment in terms of safety and antibacterial activity and we still have much to learn about their side-effects and toxicity. It is possible to have as low an endophthalmitis rate as 0.02% with no intracameral antibiotics. It is also important to note that the studies in the scientific literature show a decreased risk of endophthalmitis infection mostly in cases with as high a pre-existing endophthalmitis rate 0.2%, as seen in the as ESCRS Study, so it is probably reasonable to use intracameral antibiotics in high-risk cases,” he said. In terms of the published data, Dr Grzybowski said that the overall picture is not as coherent as many would like to believe. “The only controlled randomised prospective study was the ESCRS trial. All of the others were retrospective studies, which show a huge variation of 1.3 up to 28 times the effect from intracameral antibiotics on endophthalmitis rates, so it is not consistent. It should also be noted that none of the studies started with a very low endophthalmitis rate of 0.02-0.04%, which is quite common today in many developed countries, so there is no compelling evidence that intracameral antibiotics is effective under such conditions,” he said. Even the landmark ESCRS study should not be read as a straightforward endorsement of ICA used as prophylaxis, said Dr Grzybowski. “The ESCRS study showed about a five-fold reduction in the endophthalmitis rates with intracameral antibiotics. However, what is often overlooked is that the same study showed that there was a six times higher rate of endophthalmitis with a clear corneal incision versus scleral tunnel incision. Another interesting finding from the study was that silicone IOLs were related to a 3.13 times higher endophthalmitis rate. Yet we seem to have focused only on the use of intracameral antibiotics and forgotten about these other elements,” he said. Dr Grzybowski cited two major studies that showed no effect of ICA for routine prophylaxis, and said that many other studies have shown the effectiveness of topical antibiotics in attaining a low infection rate. “We also conducted a recent study comparing endophthalmitis rates and practice patterns in different parts of the world and we found that the infection rate in countries not using ICA is very similar to those that do use them,” he said. “I believe that the appropriate use of povidone-iodine and uncomplicated surgery with waterproof incision are much more important than IC antibiotics in standard cases.” Steve Arshinoff: ifix2is@gmail.com Andrzej Grzybowski: 
ae.grzybowski@gmail.com
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