Long-Term Intraocular Pressure Changes Following Phacoemulsification in Eyes with and Without Primary Open-Angle Glaucoma

Background and Objectives: The effect of phacoemulsification on long-term intraocular pressure (IOP) in primary open-angle glaucoma (POAG) remains incompletely defined, particularly in medically controlled disease. This study aimed to evaluate long-term IOP changes following phacoemulsification in eyes with and without POAG using longitudinal statistical modelling. Materials and Methods: This single-centre study, comprising prospective and retrospective components, included 61 patients (30 controls and 31 with medically controlled POAG) who underwent uncomplicated phacoemulsification with intraocular lens implantation. Patients were followed prospectively through six months; long-term IOP values were obtained retrospectively from routine clinical follow-up records. IOP was measured preoperatively and at 1 week, 1 month, 3 months, 6 months, and at final follow-up (44–77 months). Longitudinal IOP changes were analysed using linear mixed-effects models with a piecewise time structure to account for repeated measurements and uneven follow-up. Predictors of postoperative IOP change were evaluated using multivariable linear regression. Changes in antiglaucoma medication burden were assessed using the Wilcoxon signed-rank test. Results: A significant overall effect of time on IOP was observed (p < 0.001), with a significant early postoperative reduction (p < 0.001) followed by long-term stabilisation. No time-by-group interaction reached statistical significance, indicating broadly similar longitudinal IOP trajectories in glaucomatous and non-glaucomatous eyes. Mean preoperative IOP was 14.80 ± 2.50 mmHg in controls and 15.48 ± 3.12 mmHg in the POAG group. At final follow-up (44–77 months), mean IOP was reduced by 1.20 mmHg (8.1%) in the control group and by 1.13 mmHg (7.3%) in the POAG group relative to preoperative values. At 60 months, model-predicted IOP remained below baseline in both groups (control: 13.55 mmHg; POAG: 14.39 mmHg). Higher preoperative IOP showed the strongest association with greater postoperative IOP reduction (p < 0.001). No significant long-term change in antiglaucoma medication burden was observed in the POAG group (p = 0.157). Conclusions: Uncomplicated phacoemulsification produced a modest but sustained reduction in IOP over long-term follow-up in eyes with and without medically controlled POAG. In POAG, IOP remained below baseline over long-term follow-up, with 29 of 31 patients requiring no change in the number of topical agents. Cataract surgery alone provides a limited but durable IOP benefit in medically controlled POAG.