This study aims to determine whether a combination of vitamins (B6, B9, B12, and choline) can help protect the eyes of people with glaucoma and slow vision loss. The study will assess whether these vitamins support retinal cells and maintain or improve their function. Adults aged 18 and older with primary open-angle glaucoma (including normal-tension glaucoma) or pseudoexfoliation glaucoma, and those with mild to moderate glaucoma, may be eligible. Participants must meet specific medical criteria and cannot take additional vitamin supplements during the study. Participants will be randomly assigned to one of two groups: one group will take a daily vitamin supplement (B6, B9, B12, and choline) for one year, along with standard glaucoma care, while the other will continue standard care without extra vitamins. The vitamins used are well tolerated at selected doses, with possible mild side effects such as an upset stomach or tingling sensations. They will visit the clinic five times over 12 months (at the start, and at 3, 6, 9, and 12 months) for routine eye tests, including measuring eye pressure, checking vision and visual fields, taking scans of the eye's nerve layers (OCT), and completing an electroretinogram (ERG) to assess retinal function. Blood samples will also be collected. If the vitamins are effective, this could provide an additional strategy alongside current eye pressure lowering treatments to reduce vision loss.