Visual Field Outcomes From The Randomized, Multicenter, Horizon Trial

Minimally invasive glaucoma surgery (MIGS) with a Schlemm’s canal microstent (SCM) in combination with cataract surgery has been shown to reduce IOP, medication use, and risk of repeat glaucoma surgery. This study compares visual field outcomes after cataract surgery plus SCM with cataract surgery alone.

Prospective, multicenter, single-masked randomized controlled trial conducted at 26 sites in the US and 12 international sites. Subjects with mild to moderate primary open angle glaucoma (POAG) and visually significant cataract with washed-out diurnal IOP 22 - 34 mmHg were randomized 2:1 to cataract surgery with or without a SCM (Hydrus Micorstent, Ivantis, Irvine CA).

Medications for IOP control were reintroduced as required.  Scheduled visits including standard automated perimetry (24-2 SITA Standard) were conducted over five years follow-up. The response variable was point-wise sensitivity over time (i.e., at each tested VF location for each subject). Observations were grouped by location, VF cluster (based on the trajectory of nerve fiber bundles) and eye in a hierarchical nested fashion. Time from surgery and the allocation arm were used as fixed effects. The interaction between these fixed effects modelled the difference in rate of progression (RoP) between the two arms. 

556 eyes were randomized, after cataract surgery, to SCM (n = 369) or no further treatement (CS, n = 187). The SCM and CS groups did not differ with respect to baseline characteristics. Continuous 5-year follow up was completed in 444/556 eyes (80%). There were no significant differences in baseline sensitivity. Over 5 years of follow up, the mean RoP of VF damage was significantly slower in the SCM group compared to CS group (-0.26 dB/year vs. -0.49 dB/year, difference = 0.23 dB, 95% CI 0.5 – 0.4, p=0.0138).