• Written By:
    Cataract/Anterior Segment, Glaucoma

    Investigators evaluated the 2-year efficacy and safety of cataract surgery with the Hydrus microstent (Ivantis) implantation.

    Study design

    The HORIZON Study is a prospective, multicenter, single-masked, randomized controlled trial comparing patients undergoing combined phacoemulsification and microstent implantation with phacoemulsification alone. Patients recruited to the study had primary open-angle glaucoma (POAG), cataract and a washed-out modified diurnal IOP (MDIOP) between 22 to 34 mm Hg. After uncomplicated phacoemulsification, patients were randomized 2:1 to receive a single Hydrus microstent (n=369) in the Schlemm canal or no stent (n=187).

    Patients were followed postoperatively for 24 months; medication washout and MDIOP measurements were obtained at 12 and 24 months. Main outcomes were the proportion of patients experiencing an unmedicated MDIOP reduction or 20% or more and the change in mean MDIOP. Hypotensive medication use and adverse events were also assessed.


    At 24 months, 77.3% of stent-treated patients showed a 20% or more reduction in unmedicated MDIOP compared with 57.8% of patients who underwent cataract surgery alone (P<0.001). The microstent group exhibited a superior reduction in mean unmedicated MDIOP (-7.6 mm Hg vs. -5.3 mm Hg; P<0.001). The average washed-out MDIOP was lower in the eyes with the Hydrus device compared with controls (17.4 mm Hg vs. 19.2 mm Hg). The glaucoma implant showed success even when stricter IOP reduction criteria of 30% or 40% were applied.

    By the end of the study, 78% of eyes with the implant were medication free compared with 48% of the no-stent group. Overall, there were no significant differences in safety parameters and no serious ocular adverse events.


    Since surgeons were not masked to the treatment group, there may be potential bias in postoperative examinations. Additionally, only patients with POAG were enrolled, thereby limiting the generalizability of the results.

    Clinical significance

    As MIGS procedures become more prevalent, long-term safety and efficacy data are necessary for clinicians to choose the best procedure for their patients. The HORIZON study adds to the growing body of evidence supporting the safety and efficacy of angle procedures being done in conjunction with cataract surgery. Long term head-to-head studies comparing MIGS devices are needed to better characterize safety and efficacy among devices.