A Composite Risk Score for Capsule Complications Based on Data from the Swedish National Cataract Register: Relation to Surgery Volumes.

PURPOSE: To investigate case mix in relation to capsule complication, possible associations between case mix and operation volume, and change in case mix over time. DESIGN: Register-based study. PARTICIPANTS: Swedish patients who underwent cataract surgery between 2007 and 2016. METHODS: Demographics and data on ocular comorbidity, intraoperative difficulties, and capsule complications were registered from 2007 to 2016 and analyzed retrospectively in relation to coded data on individual surgeons' operation volume. Single factor analysis and logistic regression were performed, and a composite risk score was created. MAIN OUTCOME MEASURES: Risk of capsule complication, given as adjusted and composite odds ratio in relation to cataract surgery volume. RESULTS: Preoperative and intraoperative variables significantly associated with capsule complications were best-corrected visual acuity (BCVA) ≤0.1 (decimal, adjusted odds ratio [aOR], 1.82; P < 0.001); pseudoexfoliation (PEX) (aOR, 1.53; P < 0.001); sight-threatening ocular comorbidity other than age-related macular degeneration (AMD), diabetic retinopathy, glaucoma, or cornea guttata (aOR, 1.35; P = 0.006); use of Trypan blue (aOR, 1.76; P < 0.001); mechanical pupil dilation (aOR, 1.36; P = 0.024); and iris hooks at the rhexis margin (aOR, 6.99; P < 0.001). The composite risk score was 3.09 ± 6.40 (mean ± standard deviation) for patients with capsule complication and 1.28 ± 1.66 for uncomplicated procedures (P < 0.001). High-volume cataract surgeons (≥500 procedures yearly) had a significantly lower composite risk score (mean risk score ≤1.28; range, 1.01-2.02) compared with low- and medium-volume cataract surgeons (1.34 ± 0.56; range, 1.00-4.55 and 1.49 ± 0.58; range, 1.01-5.19), respectively. During the period 2007-2016, the proportion of patients aged >88 years, patients with BCVA ≤0.1, and patients with intraoperative difficulties decreased. CONCLUSIONS: Case mix, as calculated from a composite risk score based on preoperative and intraoperative parameters registered in the National Cataract Register (NCR), may contribute to the decrease in capsule complications from 2007 to 2016 and the lower complication rate observed in cases managed by high-volume cataract surgeons.