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Although endophthalmitis following cataract extraction is a rare complication (only 0.17% in the study by Norregaard et al presented in this issue of theBJO(p 102)), endophthalmitis is important because frequently it has a significant effect on visual function.
Outcomes of cataract surgery, including endophthalmitis, have been the subject of intense investigation in recent years, in part because cataract extraction is the most commonly performed surgery in adults in most developed nations. In response to significant regional variation in cataract surgery rates across the USA, the Cataract Patient Outcome Research Team (PORT), funded by the Agency for Health Care Policy and Research (AHCPR) in the USA, was established to assess variations in short term and long term outcomes and costs for treatment of cataracts.1 Their review of Medicare records from 1984 revealed endophthalmitis rates within 1 year of inpatient cataract surgery of 0.17% for intracapsular cataract extraction and 0.12% for extracapsular extraction or phacoemulsification.2 The PORT team found that the endophthalmitis rate within 1 year following outpatient cataract surgery performed in 1986 and 1987 was 0.08%.3
A review of the medical literature to 1991, published by the AHCPR Cataract Management Guideline Panel, found that endophthalmitis rates following cataract extraction varied from 0 to 1.89% among 12 studies, but that the confidence limits around the rates were very large owing to the relatively small size of the populations studied and the rarity of the event.4 The panel recommended the initiation of well designed, well controlled, and possibly randomised studies of alternative techniques for cataract surgery to address questions of safety. Results from such studies have not been reported in the medical literature, but there have been a number of articles related to endophthalmitis. A Medline search of 5 years of the medical literature from 1992 to 1996 using the MESH headings ‘endophthalmitis’ and ‘cataract extraction’ uncovered 142 articles, 42 (30%) of which were coded as case reports. The content of the articles varied and ranged from the case reports through to population based incidence estimates, risk factor analyses, and strategies for prophylaxis and treatment. In a review of endophthalmitis published in 1994, the authors concluded that multicentre clinical trials were necessary to assess the effectiveness of treatment regimens for endophthalmitis because the incidence is so low, but acknowledged that it was still doubtful that all possible variables could be accounted for.5 They called for a national reporting system as the first step in identifying factors for future prospective studies, but noted the possible reticence of surgeon participation in a register of adverse outcomes because of the issue of potential litigation.
Although studies such as that reported by Norregaard and colleagues are very useful because they allow us to assess the effect of various healthcare systems on outcomes of cataract surgery, it is time for another systematic review of the literature in relation to endophthalmitis following cataract extraction. The Cochrane Collaboration prepares, maintains, and disseminates the results of systematic reviews of the effect of health care from reports in the medical literature (published and unpublished) to be used as the basis for evidence based decisions in health care.6 These systematic reviews are especially useful for rare outcomes, such as endophthalmitis, when no single study is likely to provide the answers necessary for rational evidence based clinical decision making because the incidence of endophthalmitis is so low.7 It is, nevertheless, very important because potentially it is one of the complications of cataract extraction that is the most visually disabling. With the overall success of cataract surgery very high, it is now important to elucidate the incidence, risk factors, and most effective treatment of the major complications of cataract extraction, including endophthalmitis. A systematic review of the extensive literature on endophthalmitis following cataract extraction could dramatically improve our understanding of this complication and save the vast resources that would be required to conduct a multicentred trial that is not assured of success. The results of a systematic review could also be used effectively to direct future prospective trials. The Cochrane Database of Systematic Reviews currently allows the rapid dissemination of results from completed reviews and in the future will allow the direct entry of data and immediate update of the register. The time has come for evidence based medicine, and management of endophthalmitis following cataract extraction is in need of an evidence base and systematic review.