Objective: To evaluate the long-term evolution of first-line glaucoma therapy (FLGT) initiated by ophthalmologists and optometrists., Design: Retrospective population-based study using validated provincial health care databases., Participants: 194,759 Ontario residents, 66 years of age or older, who received FLGT between 2007 and 2018., Methods: A total of 194,759 individuals from 12 annual cohorts were enrolled, and rates of first-line medical treatment (prostaglandin analogue [PGA], beta-blocker, alpha-2-agonist, and carbonic anhydrase inhibitor) and laser trabeculoplasty (LT) were calculated. Provider (ophthalmologist or optometrist) rates also were assessed., Results: Across the entire study period, of the 194,759 enrolled individuals who received FLGT, 60.2% initially received medical treatment and 39.8% underwent LT. Approximately 94.6% were treated by ophthalmologists. PGA therapy was the most common therapy prior to 2010, whereupon LT became the most common FLGT. By 2015, LT exceeded the total of all medications as FLGT. The annual rate of initial medication prescriptions by optometrists rose to 101.4 per 100,000 population between 2011 and 2018. In 2018, PGA and non-PGA prescription rates by ophthalmologists were 2.6 and 5.0 times higher, respectively, than prescription rates by optometrists., Conclusion: LT therapy has become the most common FLGT for Ontario residents 66 years of age or older. PGAs remain the most frequently prescribed glaucoma medication. While ophthalmologists continue to provide the majority of FLGT, optometrists now provide a small but growing fraction of FLGT following the introduction of glaucoma medication prescribing privileges., Competing Interests: Footnotes and Disclosure None of the authors has any conflicts of interest to disclose. This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC). This study was based on data compiled by ICES. Parts of this material are based on data and information compiled and provided by the Ontario MOH and MLTC, Ontario Health Insurance Plan (OHIP) database, Ontario Drug Benefit (ODB) database and IQVIA Solutions Canada, Inc., Ontario Registered Persons database, and ICES Physician database. The analyses, conclusions, opinions, and statements expressed herein are solely those of the authors and do not reflect those of the funding or data sources; no endorsement is intended or should be inferred. Robert J. Campbell is supported by the David Barsky Chair in Ophthalmology and Visual Sciences, Queen's University, Kingston, Ontario. Data access and responsibility: ICES is an independent, nonprofit research institute funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC). As a prescribed entity under Ontario's privacy legislation, ICES is authorized to collect and use health care data for the purposes of health system analysis, evaluation, and decision support. Secure access to these data is governed by policies and procedures that are approved by the Information and Privacy Commissioner of Ontario. The data sets from this study are held securely in coded form at ICES. These data sets were linked using unique encoded identifiers and analyzed at ICES. Robert J. Campbell had full access to the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Author contributions: Robert J. Campbell was responsible for conception and design of the study, data acquisition and interpretation, manuscript drafting and revision, approval of the final version, and overall study accountability. Katharine Doliszny was responsible for study design, data acquisition and interpretation, manuscript drafting and revision, approval of the final version, and overall study accountability. Marlo Whitehead was responsible for study design, data acquisition and interpretation, manuscript revision, approval of the final version, and overall study accountability. Matthew P. Quinn, Sherif R. El-Defrawy, Sudeep S. Gill, and Davin Johnson were responsible for interpretation of the results, revision and approval of the manuscript, and overall study accountability., (Copyright © 2022 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.)