RecruitingDevice studyChange in IOP Fluctuation After DSLTThis is a prospective, single-center, single-arm, observational study designed to evaluate the change in diurnal intraocular pressure (IOP) fluctuation following Direct Selective Laser Trabeculoplasty (DSLT) in patients with primary open-angle glaucoma (POAG) who are on 1-3 IOP lowering medications. The study will be conducted at one site and will involve three key visits: a screening visit, a baseline/treatment visit, and a 6-month follow-up visit. During the screening visit, patients will undergo a comprehensive ophthalmic examination, and eligibility will be confirmed. The eye with the higher IOP will be selected if both eyes are eligible. At the baseline visit, diurnal IOP will be recorded at three time points (9am, 12pm, and 4pm) before DSLT is performed. The primary endpoint is the change in diurnal IOP fluctuation 6 months post-treatment. Secondary endpoints include changes in mean diurnal IOP and the proportion of eyes achieving a reduction in IOP fluctuations of ≥1 mmHg. Exploratory endpoints focus on demographic variables associated with IOP fluctuation changes.