Risk Factors for Acute Endophthalmitis after Cataract Surgery: A Population-based Study Wendy V. Hatch, OD, MSc, 1,2 Geta Cernat, MD, 3 David Wong, MD, FRCS(C), 7 Robert Devenyi, MD, FRCS(C), 1,2 Chaim M. Bell, MD, PhD 3,4,5,6 Objective: To identify risk factors for suspected acute endophthalmitis after cataract surgery. Design: Population-based retrospective cohort. Participants: Administrative data from more than 440,000 consecutive cataract surgeries in Ontario, Can- ada, from April 1, 2002, to March 31, 2006. Methods: Consecutive physician billing claims for cataract surgery and specific intraoperative and postop- erative procedures related to complications of cataract surgery were identified. Acute endophthalmitis was defined using surrogate markers for intraocular infection, including vitrectomy, vitreous injection, or aspiration procedures not in combination with air/fluid exchange or dislocated lens extraction, performed 1 to 14 days after cataract surgery. Anterior vitrectomy performed on the day of surgery was used as a surrogate marker for capsular rupture. Main Outcome Measures: Overall rates of endophthalmitis were calculated and grouped by patient demographics, surgical facility, season, year, and association with capsular rupture. Results: There were 617 suspected acute endophthalmitis cases of 442,177 cataract surgeries over the 4 years. The overall unadjusted and adjusted rates of suspected acute endophthalmitis were both 1.4 per 1000 cataract surgeries. Men had higher rates than women (1.70 vs. 1.19/1000 surgeries, P0.0001) with an adjusted odds ratio of 1.40 (95% confidence interval, 1.19 –1.64).The oldest age group (85 years) had the highest rate (2.18/1000), and the youngest group (20 – 64) had the second highest rate (1.76/1000). The endophthalmitis rates for these age groups were significantly different from those aged 65 to 84 years. The endophthalmitis rate was approximately 10-fold higher in those with capsular rupture compared with those without (13.11 vs. 1.34/1000, P0.0001), with an adjusted odds ratio of 9.56 (95% confidence interval, 6.43–14.2). Conclusions: The overall rates of suspected acute endophthalmitis are low but significantly higher in certain patient groups. Our population-based analysis can be used as a benchmark for quality-improvement initiatives and can assist clinicians in educating their patients regarding the risks associated with cataract surgery. Future work is required to address the higher rate of endophthalmitis in men, those with capsular rupture, and the oldest patients undergoing cataract surgery. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. Ophthalmology 2009;116:425– 430 © 2009 by the American Academy of Ophthalmology. Endophthalmitis is a rare but serious postoperative compli- cation of cataract surgery. Many studies have estimated rates and identified risks for the condition. 1–5 These studies are often limited by a small number of cases or by data that are collected over many years, resulting in outcome ascer- tainment difficulties. One large, population-based study used a sample of approximately half a million US Medicare claims for cataract surgeries from 1994 to 2001 and found that rates increased substantially over this time, and that older age and black race were associated with increased risk of endophthalmitis. 1 A recent Swedish study of more than 200,000 cataract surgeries found risk factors included com- munication between the anterior segment and vitreous, pa- tients aged 85 years and more, and the nonuse of intracam- eral cefuroxime. 5 Neither of these studies found a difference in rates between men and women. Previous studies have also identified associated risk factors, such as season of surgery 4,6 and ruptured capsule during surgery, 7 and found no difference when they compared endophthalmitis rates of patients living in rural and remote areas. 4 Because endophthalmitis rates are low, smaller studies often have insufficient power to detect differences between groups. In addition, even fairly recent studies may not be representative of the current era; the rapidly evolving sur- gical techniques and indications for cataract surgery that have become common practice in the 21st century may confer different risks for endophthalmitis. To address these issues, we identified and tested for potential risks for en- dophthalmitis after cataract surgery using population-based administrative data from more than 440,000 consecutive cataract surgeries in Ontario, Canada, from April 1, 2002, to March 31, 2006. 425 © 2009 by the American Academy of Ophthalmology ISSN 0161-6420/09/$–see front matter Published by Elsevier Inc. doi:10.1016/j.ophtha.2008.09.039