Long-term Outcomes from the HORIZON Randomized Trial for a Schlemm's Canal Microstent in Combination Cataract and Glaucoma Surgery

Abstract

Purpose: To present the 5-year results of the HORIZON trial comparing cataract surgery (CS) combined with an intracanalicular microstent with CS alone.

Design: Prospective, multicenter, controlled randomized clinical trial.

Participants: Patients with cataract and primary open-angle glaucoma treated with 1 or more glaucoma medications, washed-out diurnal intraocular pressure (DIOP) of 22 to 34 mmHg, and no prior incisional glaucoma surgery.

Methods: Eyes were randomized 2:1 to receive a Hydrus Microstent (HMS; Ivantis, Inc) or no stent after successful CS.

Main outcome measures: Intraocular pressure (IOP), glaucoma medication use, repeat glaucoma surgery, visual acuity, visual field, procedure-related adverse events, and corneal endothelial cell counts.

Results: Three hundred sixty-nine eyes were randomized to HMS treatment, and 187 eyes were randomized to CS only. Study groups were well matched for preoperative IOP, medication use, washed-out DIOP, and glaucoma severity. Five-year follow-up was completed in 80% of patients. At 5 years, the HMS group included a higher proportion of eyes with IOP of 18 mmHg or less without medications than the CS group (49.5% vs. 33.8%; P = 0.003), as well as a greater likelihood of IOP reduction of 20% or more without medications than the CS group (54.2% vs. 32.8%; P < 0.001). The number of glaucoma medications was 0.5 ± 0.9 in the HMS group and 0.9 ± 0.9 in the CS group (P < 0.001), and 66% of eyes in the HMS group were medication free compared with 46% in the CS group (P < 0.001). The cumulative risk of incisional glaucoma surgery was lower in the HMS group (2.4% vs. 6.2%; P = 0.027, log-rank test). No clinical or statistically significant differences were found in the rate of endothelial cell loss from 3 to 60 months between the HMS and CS alone groups (P = 0.261).

Conclusions: The addition of a Schlemm's canal microstent in conjunction with CS was safe, resulted in lowered IOP and medication use, and reduced the need for postoperative incisional glaucoma filtration surgery compared with CS after 5 years. Long-term presence of the implant did not affect the corneal endothelium adversely.

Keywords: Glaucoma medication usage; Intraocular pressure; Microinvasive glaucoma surgery; Schlemm’s canal microstent.