Surgeon volumes and selected patient outcomes in cataract surgery - A population-based analysis

Objective: To study the association of annual surgeon volume of cataract procedures with the risk of postoperative adverse events. Design: We used population-based administrative health records to conduct a retrospective cohort study from 2001 through 2003. Participants: The number of surgeons who performed more than 50 cataract surgeries annually ranged from 231 to 243 over the 3 years. There were 284 797 cataract surgeries in patients older than 20 years performed at 70 hospitals or eye surgery centers in the province of Ontario, Canada. Methods: We calculated cataract surgery volume for each surgeon and tested for the presence of a volume-outcome association. We used generalized estimating equations to account for the effect of clustering of patients according to individual surgeons and to adjust estimates for the potential confounding effects of patient age and gender. Main Outcome Measures: We used a composite outcome of postoperative adverse events from cataract surgery that included billing claims for vitrectomy, vitreous aspiration or injection of medication, vitreous air or fluid exchange, and dislocated lens extraction performed by any ophthalmologist between 1 and 14 days after cataract surgery. These procedures are surrogate markers for the outcomes of retinal detachment, lost lens or lens fragment, and suspected endophthalmitis. Results: In each year, fewer than 1 in 200 patients experienced an adverse event (range, 0.33%-0.41 %). Surgeons performing 50 to 250 cataract surgeries per year had an adverse event rate of 0.8%. Surgeons performing 251 to 500 cataract surgeries per year had an adverse event rate of 0.4% and an adjusted odds ratio of postoperative adverse events of 0.52 (95% confidence interval [CI], 0.39-0.69) compared with surgeons performing 50 to 250 procedures per year. Surgeons performing 501 to 1000 cataract surgeries per year had an adverse event rate of 0.2% and an adjusted odds ratio of 0.31 (95% Cl, 0.22-0.43), and surgeons performing more than 1000 cataract surgeries per year had an adverse event rate of 0.1 % and an adjusted odds ratio of 0.14 (95% Cl, 0.09-0.23). Conclusions: Selected adverse event rates for surgeons performing more than 50 cataract surgeries per year are low. There is a volume-outcomes relationship for cataract surgery, and this relationship persists even for very high-volume surgeons.