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At the ESCRS congress in September, Peter Barry presented the full ESCRS endophthalmitis study results and controversially stated that, not only is the incidence of endophthalmitis higher than reported in the literature, but the risk of infection is further increased by clear corneal incisions and the use of silicon IOLs.
The incidence and effective treatment of endophthalmitis was certainly a hot topic at this year's meeting in London and Professor David Seal, MD, of City University, London, UK, also used this opportunity to delve deeper into understanding the infection feared by all ophthalmic surgeons. He communicated his findings to an audience at the Santen-sponsored lunch symposium during the congress.
Do clear corneal incisions influence infection rate?
Taban and his team performed a systematic review of articles published from 1963 to March 2003 and assessed pooled incidence rates and relative risks of developing endophthalmitis following cataract extraction using different incision techniques.
The research team noted an increase in endophthalmitis cases over time, with the rate of clear cornea incision phaco in the USA and Europe reaching 72% and 52%, respectively. Taban hypothesized that the integrity of a clear cornea incision was critical and he attributed the increased rate of endophthalmitis to this incision because up to 80% of post-cataract surgery endophthalmitis was found to be associated with wound defects, gaping and leakage.
Sweden vs. Europe: the studies
As part of his research, Professor Seal compared two different, large-scale endophthalmitis studies: the Swedish cataract surgery registry study, which enrolled 225,000 patients in Sweden and the ESCRS study, which enrolled 15,971 subjects in 24 centres across nine EU states. Professor Seal was the co-ordinator of the ESCRS study. Of the 15,971 ESCRS subjects, he chose to focus on those 50% who were randomized to receive intracameral cefuroxime with postoperative levofloxacin (8,150 patients), hence all references to ESCRS study subjects from here on in refer to this portion of patients.
By looking at the study designs and outcomes, it was Professor Seal's aim to establish an effective prophylaxis method for this devastating infection.
Although the overall endophthalmitis rate was similar in the Swedish and the ESCRS study groups (0.05% versus 0.06%, respectively), the prophylaxis modalities did vary between the two with the Swedish study using aqueous chlorhexidine followed by perioperative intracameral cefuroxime without postoperative antibiotics and the ESCRS study employing povidone iodine, intracameral cefuroxime and postoperative levofloxacin.
Upon close evaluation of the organisms present in each of the study groups, Seal found a significant difference in pathogen-induced endophthalmitis between the two groups. While Staphylococcus aureus, coagulase-negative staphylococcus,streptococci and enterococci were present in 0.004%, 0.015%, 0.003% and 0.011% of patients in the Swedish group, respectively, the ESCRS study only recorded three cases (0.037%) of coagulase-negative staphylococcus, with all other organisms being absent from study samples.
"Although the overall endophthalmitis incidence was similar between the two groups, there have been cases of endophthalmitis in Sweden that are difficult to explain," said Professor Seal. "The bacteria identified in the Swedish study should, in most cases, have been sensitive to the intracameral cefuroxime, but infections still occurred with them. On the other hand, there were no cases of endophthalmitis caused by these bacteria in the ESCRS study," he stated. "We need to question why this happened."
It was hypothesized by Taban and his team that infection can occur postoperatively through the clear cornea incision wound. "This theory leads me to believe that these cases of endophthalmitis in Sweden could have been prevented with postoperative antibiotics," said Seal. He attributes the reduced bacterial count witnessed in the ESCRS study to the postoperative administration of the newer generation quinolone antibiotic, levofloxacin.