Effect of Niacinamide Supplementation in Glaucoma

100 subjects with primary open-angle glaucoma will be enrolled from two centres (CMI profesor doctor Liliana Mary Voinea Bucharest Eye Centre and SC Optispecs Med SRL TgJiu Eye Clinic). Participant Selection P1. Inclusion criteria A subject will be eligible for inclusion in this study only if all of the following criteria apply: * Patients aged 18 years or older; * Confirmed diagnosis of Primary Open angle Glaucoma (POAG) - following a complete ophthalmological examination (ocular tonometry, slit lamp ocular examination, visual field and Optical coherence tomography); * Subject has provided signed and dated written informed consent before admission to the study. * Subject is able to understand and comply with the protocol requirements, instructions, and protocol-stated restrictions. * Participants need to have visual acuity of Snellen ≥ 6/12 (0.5) or better. * Have performed at least two reliable VFs (SITA-Fast 24-2), with \<33% fixation losses and \<15% false positives * Those taking NAM already will undergo a 1-month washout period before commencing the study. P2. Exclusion criteria A subject will not be eligible for inclusion in this study if any of the following criteria apply: * Participants must not be pregnant or breastfeeding women; * Investigator considers the subject unfit for the study as a result of medical history, physical examination, or screening tests; * VF damage worse than -10dB in the best eye and -16dB in the worse eye or a paracentral spot with -10dB or less in any eye), * IOP \>35mmHg in any eye or a mean IOP of 30mmHg or higher (two measurements), •inability to perform VFs, * those unwilling to abstain from NAM supplements, * allergic to niacinamide/niacin, * diagnosed with cancer in the last 5 years (except treated basal or squamous cell carcinoma), * a history of liver disease or stomach ulcers, * disease that prevents long-term follow-up, * neurologic or other non-glaucomatous conditions apart from cataract that may affect the VF * Patient is diagnosed with primary angle closure glaucoma; * Patient is diagnosed with secondary glaucoma (e.g. posttraumatic, postinflammatory, steroid induced, pseudoexfoliative, pigmentary, etc.); * Patient is diagnosed with very advanced glaucoma (foveal fixation threatened or absent and, thus, unreliable perimetry); * Patient is diagnosed with other significant ocular pathologies (advanced cataract, pathologic myopia, corneal ectasias or dystrophies, sever amblyopia, vitreoretinal disease, active ocular inflammation, significant sequelae of ocular inflammation); * Unreliable ophthalmological investigations and non-compliance with examinations (e.g. high percentage of false negative and false positive errors when examining the visual field). Participants will: * Take NAM every day for 1 year * Visit the clinic at 3, 6, and 12 months for check-ups and tests Outcome Measures M1. Ophthalmological parameters * Visual field parameters: * Mean deviation (MD) * Pattern standard deviation (PSD) * Optical coherence tomography parameters: peripapillary retinal nerve fiber layer thickness (pRNFL); * Visually evoked potential parameter: latence of P2 wave when using a flash stimulus. M2. Quality of life measurement ➔ Glaucoma Quality of Life-15 questionnaire