Incidence of endophthalmitis after corneal transplant or cataract surgery in a medicare population

Objective: To estimate the incidence of infectious endophthalmitis after corneal transplant or cataract surgery, to evaluate the trend of endophthalmitis during the study period, and to assess demographic risk factors for endophthalmitis after surgeries.

Design: A retrospective population-based cohort study.

Participants and controls: Study cohorts were derived from the Medicare claims databases, 2006 to 2011. Patients were continuously enrolled in Medicare Part A, Part B, and Part D. Patients undergoing corneal transplant or cataract surgery were identified using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes.

Methods: Endophthalmitis was defined in 3 different ways: (1) using ICD-9-CM codes (sensitive definition), (2) combining ICD-9-CM codes with Current Procedural Terminology, Fourth Edition (CPT-4) codes (specific definition), or (3) combining ICD-9-CM codes with antifungal prescriptions for endophthalmitis caused by fungal infection. Demographic risk factors for endophthalmitis were examined using multivariate Cox models.

Main outcome measures: Incidence rates of endophthalmitis were calculated and compared for each definition of endophthalmitis at 6-week and 6-month intervals after corneal transplant or cataract surgery.

Results: The infectious endophthalmitis incidence rates ranged from 0.11% to 1.05% in the corneal transplant cohort, 0.06% to 0.20% in the cataract surgery cohort, and 0.16% to 0.68% in the concurrent surgery cohort, depending on the definition and time interval after surgery. Compared with the cataract surgery cohort, the corneal transplant cohort had a higher adjusted hazard ratio (HR) of endophthalmitis within the 6-week postoperative interval (HR, 2.744; 95% confidence interval [CI], 1.544-4.880 in the sensitive definition and HR, 2.792; 95% CI, 1.146-6.802 in the specific definition) and within the 6-month postoperative interval (HR, 4.607; 95% CI, 3.144-6.752 for the sensitive definition and HR, 4.385; 95% CI, 2.245-8.566 for the specific definition).

Conclusions: It is possible to monitor the trend of infectious endophthalmitis after corneal transplant or cataract surgery through examining Medicare claims databases as long as a consistent definition of endophthalmitis is used. The annual incidence of endophthalmitis was stable over time during the study period for both corneal transplant and cataract surgery procedures; however, there was a wider year-to-year variation for the corneal transplant cohort.