Comparison of Phacoemulsification Alone and With Trabecular Microbypass Stent in Primary Open-Angle Glaucoma and Normal-Tension Glaucoma: An 18-Month Outcome Study

iStent (Glaukos, San Clemente, CA, USA), a minimally invasive glaucoma device, reduces intraocular pressure (IOP) by enhancing aqueous humor outflow when implanted into Schlemm's canal. Although it has demonstrated effectiveness in lowering IOP and slowing glaucoma progression, its applicability to the Taiwanese population, known for a higher incidence of normal-tension glaucoma (NTG) cases, requires validation. This retrospective case-control study, conducted from January 2018 to December 2020, aimed to assess the effectiveness of combining first-generation iStent with phacoemulsification (phaco-iStent) compared to phacoemulsification alone in Taiwanese patients diagnosed with primary open-angle glaucoma (POAG) and NTG, involving 71 eyes (iStent group: POAG 16 and NTG 8; control group: POAG 28 and NTG 19). The primary outcomes included changes in IOP and the number of antiglaucoma medications, with subgroup analyses for POAG and NTG. Over the 18-month follow-up, the iStent group achieved a significantly greater reduction in antiglaucoma medications compared with the control group (p value = 0.003∼<0.001) without significant IOP rebound. After adjusting for confounding factors, the reduction in the number of antiglaucoma medications with iStent remained significant (β = -0.8, p < 0.001) according to the generalized estimating equation. At 18 months, the iStent group demonstrated higher qualified and complete success rates than the control group (73.3% vs. 16.7%, p value = 0.001% and 53.3% vs. 0%, p value = 0.002, respectively). Notably, the NTG-iStent subgroup achieved the highest complete success rate (85.7% at 18 months). In conclusion, phaco-iStent emerges as an effective standalone treatment for Taiwanese patients with POAG and NTG, providing substantial IOP reduction and higher success rates, especially in NTG cases. These findings propose that phaco-iStent could be a promising intervention for managing POAG and NTG within the Taiwanese population. Trial Registration: ClinicalTrials.gov identifier: NCT06630546.