Surgical waste and greenhouse gas emissions in cataract surgery: a multicenter interventional study at ten Japanese hospitals

Purpose To quantify waste and greenhouse gas (GHG) emissions from disposable materials used in cataract surgery in Japan and to assess pragmatic, site-selected waste-reduction interventions. Study design Prospective multicenter observational and interventional (before and after) clinical study. Methods Ten Japanese sites audited 10 consecutive standard phacoemulsification cases at baseline and after implementing low-risk intervention selected by each site and integrated into routine workflow. Disposable items were collected and weighed. GHG emissions were estimated as a partial footprint attributable to disposable materials, expressed as carbon dioxide equivalents (CO 2 eq), using published material emission factors and material-specific end-of-life assumptions. Primary outcomes were waste weight and GHG emissions per case. Results A total of 201 surgical procedures were analyzed (100 baseline, 101 post-intervention). Baseline mean waste was 2.28 ± 0.40 kg and mean GHG emissions were 9.80 ± 2.14 kg CO 2 eq per case; plastics were the largest contributor. Site-level medians decreased from 2.28 to 2.06 kg (P = .020) and from 9.09 to 8.35 kg CO 2 eq (P = .004). In mixed-effects models, reductions did not reach statistical significance (waste ratio 0.86, 95% CI 0.73–1.02, P = .092; GHG ratio 0.84, 95% CI 0.71–1.00, P = .051). Conclusions Cataract surgery in Japanese sites generates substantial disposable-material waste and associated CO 2 eq. Pragmatic site-selected interventions were associated with significant reductions in site-summary analyses, while case-level modeling showed similar trends without statistical significance, suggesting heterogeneity and/or limited power.