PURPOSE: To characterize operative and nonoperative risks for the potentially blinding complication of endophthalmitis after cataract surgery.SETTING: Ophthalmology services for the whole state of Western Australia.METHODS: This retrospective population-based nested case-control study in Western Australia covered the period between 1980 and 2000. For each of the 205 cases of enclophthalmitis, 4 time-matched controls were randomly selected from all cataract operations performed in the state. Conditional logistic regression was used to estimate multivariate adjusted odds ratios (ORs) and 95% confidence intervals (Cls) for the risk factors of interest.RESULTS: Wound location, suturing the wound, and type of cataract operation did not affect the risk for postoperative enclophthalmitis. Antibiotic prophylaxis reduced the risk, but only if given as a subconjunctival injection (OR, 0.46; 95% Cl, 0.29-0.70). The risk for enclophthalmitis was greater with same-day surgery (OR, 2.27; 95% Cl, 1.52-3.41) than with admission the day before surgery. A concurrent eyelid procedure was a substantial risk. Surgeons within 2 years of obtaining specialist qualifications were more likely to have a case of enclophthalmitis, although this was partly the result of more posterior capsule breaches. Posterior capsule breach increased the risk when it occurred in private hospitals (OR, 13.57; 95% Cl, 4.00-45.99), but not in public hospitals.CONCLUSIONS: Nonoperative as well as operative factors are important in the prevention of endophthalmitis. Subconjunctival injection of antibiotics appears to be beneficial for enclophthalmitis prophylaxis. The model showed that active risk management strategies designed to optimize hospitalization and chemoprophylaxis may reduce the incidence of endophthalmitis by up to 81%.