Objective: To evaluate whether treatment patterns for endophthalmitis after cataract surgery in American Academy of Ophthalmology IRIS® (Intelligent Research in Sight) Registry patients are in line with evidence-based guidelines established by the 1995 Endophthalmitis Vitrectomy Study (EVS), which showed that patients who present with light perception (LP) vision have better visual outcomes with immediate vitrectomy (VIT) compared with vitreous tap with antibiotic injection (TAP)., Design: Retrospective cohort study., Subjects: Intelligent Research in Sight Registry patients undergoing cataract surgery between 2014 and 2022 (identified by Current Procedural Terminology codes), presenting with endophthalmitis (identified by International Classification of Diseases 10 codes) within 42 days postcataract surgery, and having a record of being treated with VIT or TAP on the same or 1 day after endophthalmitis diagnosis were identified., Methods: Potential covariates of age, sex, race, ethnicity, geographic region, insurance status, and visual acuity on the day of endophthalmitis diagnosis were evaluated using multivariable logistic regression., Main Outcome Measures: Treatment with VIT or TAP., Results: Of the 2425 patients who met the inclusion criteria, 14% (345) underwent VIT and 86% (2080) underwent TAP. Notably, 80% of patients (1946) presented with endophthalmitis within 14 days from cataract surgery (median = 6 days). Notably, 66% (173/263) of the patients presenting with LP vision underwent TAP instead of VIT. In a multivariable logistic regression model, receiving VIT instead of TAP was positively associated with poor vision at endophthalmitis presentation (LP - odds ratio [OR] = 5.4; confidence interval [CI], 2.9-10.6; counting fingers, hand motions - OR = 1.9; CI, 1.1-3.6) versus (20/20-20/40) vision; Asian versus White race (OR = 2.6; CI, 1.3-5.2); Hispanic versus non-Hispanic ethnicity (OR = 1.9; CI, 1.1-3.2); living in the West (OR = 1.6; CI, 1.1-2.2) and Midwest (OR = 1.5; CI, 1.1-2.0) (vs. South), but not with age, sex, and insurance coverage (P > 0.05)., Conclusions: In the IRIS Registry, treatment patterns for postcataract surgery endophthalmitis did not match evidence-based recommendations of the EVS, a randomized controlled clinical trial. More work is needed to evaluate whether the current treatment patterns are optimal for patients with postcataract surgery endophthalmitis., Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article., (Copyright © 2024 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)