Background: Newly diagnosed open-angle glaucoma (OAG) and ocular hypertension (OHT) are habitually treated with intraocular pressure (IOP)-lowering eyedrops. Selective laser trabeculoplasty (SLT) is a safe alternative to drops and is rarely used as first-line treatment., Objectives: To compare health-related quality of life (HRQoL) in newly diagnosed, treatment-naive patients with OAG or OHT, treated with two treatment pathways: topical IOP-lowering medication from the outset (Medicine-1st) or primary SLT followed by topical medications as required (Laser-1st). We also compared the clinical effectiveness and cost-effectiveness of the two pathways., Design: A 36-month pragmatic, unmasked, multicentre randomised controlled trial., Settings: Six collaborating specialist glaucoma clinics across the UK., Participants: Newly diagnosed patients with OAG or OHT in one or both eyes who were aged ≥ 18 years and able to provide informed consent and read and understand English. Patients needed to qualify for treatment, be able to perform a reliable visual field (VF) test and have visual acuity of at least 6 out of 36 in the study eye. Patients with VF loss mean deviation worse than -12 dB in the better eye or -15 dB in the worse eye were excluded. Patients were also excluded if they had congenital, early childhood or secondary glaucoma or ocular comorbidities; if they had any previous ocular surgery except phacoemulsification, at least 1 year prior to recruitment or any active treatment for ophthalmic conditions; if they were pregnant; or if they were unable to use topical medical therapy or had contraindications to SLT., Interventions: SLT according to a predefined protocol compared with IOP-lowering eyedrops, as per national guidelines., Main Outcome Measures: The primary outcome was HRQoL at 3 years [as measured using the EuroQol-5 Dimensions, five-level version (EQ-5D-5L) questionnaire]. Secondary outcomes were cost and cost-effectiveness, disease-specific HRQoL, clinical effectiveness and safety., Results: Of the 718 patients enrolled, 356 were randomised to Laser-1st (initial SLT followed by routine medical treatment) and 362 to Medicine-1st (routine medical treatment only). A total of 652 (91%) patients returned the primary outcome questionnaire at 36 months. The EQ-5D-5L score was not significantly different between the two arms [adjusted mean difference (Laser-1st - Medicine-1st) 0.01, 95% confidence interval (CI) -0.01 to 0.03; p = 0.23] at 36 months. Over 36 months, the proportion of visits at which IOP was within the target range was higher in the Laser-1st arm (93.0%, 95% CI 91.9% to 94.0%) than in the Medicine-1st arm (91.3%, 95% CI 89.9% to 92.5%), with IOP-lowering glaucoma surgery required in 0 and 11 patients, respectively. There was a 97% probability of Laser-1st being more cost-effective than Medicine-1st for the NHS, at a willingness to pay for a quality-adjusted life-year of £20,000, with a reduction in ophthalmology costs of £458 per patient (95% of bootstrap iterations between -£585 and -£345)., Limitation: An unmasked design, although a limitation, was essential to capture any treatment effects on patients' perception. The EQ-5D-5L questionnaire is a generic tool used in multiple settings and may not have been the most sensitive tool to investigate HRQoL., Conclusions: Compared with medication, SLT provided a stable, drop-free IOP control to 74.2% of patients for at least 3 years, with a reduced need for surgery, lower cost and comparable HRQoL. Based on the evidence, SLT seems to be the most cost-effective first-line treatment option for OAG and OHT, also providing better clinical outcomes., Future Work: Longitudinal research into the clinical efficacy of SLT as a first-line treatment will specify the long-term differences of disease progression, treatment intensity and ocular surgery rates between the two pathways., Trial Registration: Current Controlled Trials ISRCTN32038223., Funding: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment ; Vol. 23, No. 31. See the NIHR Journals Library website for further project information., Competing Interests: Gus Gazzard, David Garway-Heath, Rachael Hunter, Gareth Ambler, Catey Bunce, Richard Wormald, Keith Barton, Gary Rubin and Marta Buszewicz have received a grant from the National Institute for Health Research (NIHR) for the submitted work. Gus Gazzard reports grants from Lumenis (Borehamwood, UK) during the conduct of the study; grants from Ellex Medical Lasers (Adelaide, SA, Australia), Ivantis, Inc. (Irvine, CA, USA) and Thea Pharmaceuticals (Keele, UK) outside the submitted work; and personal fees from Allergan (Dublin, Ireland), Alcon (Fort Worth, TX, USA), Glaukos Corporation (San Clemente, CA, USA), Santen Pharmaceutical Co., Ltd (Osaka, Japan) and Thea Pharmaceuticals outside the submitted work. David Garway-Heath reports personal fees from Aerie Pharmaceuticals, Inc. (Durham, NC, USA), Alcon, Allergan, Bausch + Lomb (Rochester, NY, USA), Quark Pharmaceuticals, Inc. (Ness Ziona, Israel), Quethera Limited and Roche (Basel, Switzerland); grants from the Alcon Research Institute; and grants and personal fees from Pfizer (New York, NY, USA) and Santen Pharmaceutical Co., Ltd, outside the submitted work. In addition, David Garway-Heath was a member of the Health Technology Assessment (HTA) Clinical Trials Board from 2014 to 2017. Keith Barton received a grant from NIHR for the Treatment of Advanced Glaucoma Study during the conduct of the study. In addition, Keith Barton reports grants from Johnson & Johnson Vision (Santa Ana, CA, USA), New World Medical (Rancho Cucamonga, CA, USA), Alcon, Merck & Co. (Kenilworth, NJ, USA), Allergan and Refocus Group (Dallas, TX, USA); that he has had other financial relationships with Alcon, Merck & Co., Allergan, Refocus, AqueSys Inc. (Taipei, Taiwan), Ivantis, Carl Zeiss Meditec AG (Jena, Germany), Kowa Europe GmbH (Düsseldorf, Germany), Santen Pharmaceutical Co., Ltd, Transcend Medical (Scottsboro, AL, USA), Glaukos (San Clemente, CA, USA), Amakem NV (Diepenbeek, Belgium), Thea Pharmaceuticals, Alimera Sciences (Alpharette, GA, USA), Pfizer, Advanced Ophthalmic Implants Pte Ltd (Singapore), Vision Futures (UK) Ltd (London, UK), London Claremont Clinic Ltd (London, UK) and Vision Medical Events Ltd (London, UK), outside the submitted work; and that he has a patent with Ophthalmic Implants (PTE) Ltd. Stephen Morris was a member of NIHR Health Services and Delivery Research (HSDR) Research Funding Board (2014–19), the NIHR HSDR Commissioned Board (2014–16), the NIHR HSDR Evidence Synthesis Sub Board (2016), the NIHR HTA Clinical Evaluation and Trials Board (2007–10), the NIHR HTA Commissioning Board (2009–13), the NIHR Public Health Research Funding Board (2011–17) and the NIHR Programme Grants for Applied Research expert subpanel (2017–present). Marta Buszewicz was a member of the HTA Mental Health Panel from January to May 2018. In September 2018 this panel was amalgamated into the HTA Prioritisation Committee C (mental health, women and children’s health), of which Marta Buszewicz was also a member. Marta Buszewicz has also been a member of the NIHR Research for Patient Benefit, London, funding panel since May 2017.