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Reduced need for glaucoma surgery 4 years after combined Schlemm’s canal microstent and cataract surgery for primary open angle glaucoma

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First Author: G.Gazzard UK

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Abstract Details


Several micro invasive glaucoma surgery (MIGS) techniques combined with cataract surgery have been shown to reduce IOP and medication use postoperatively from 6 months to 2 years in randomized clinical trials. The purpose of this study was to assess 4-year outcomes in patients who underwent cataract surgery alone compared to those who underwent cataract surgery combined with implantation of a Hydrus® Microstent.


Tertiary specialist glaucoma centres participating in the RCT.


Subjects with primary open angle glaucoma (POAG) and visually significant cataract with washed-out diurnal IOP 22 - 34 mmHg were randomized 2:1 to undergo cataract surgery with or without a Hydrus Microstent in the HORIZON study.1 Scheduled study visits were conducted through 48 months postoperative.


556 eyes were randomized after cataract surgery to Hydrus (HS, N=369) or no further treatement (CS, N=187). The HS and CS groups did not differ with respect to baseline characteristics. At screening, IOP and glaucoma status were comparable in both groups for the following: mean number of IOP lowering medications in HS vs. CS groups (1.7 ± 0.9 for both, p=0.9), pre-washout IOP (17.9 ± 3.1 mmHg vs 18.1 ± 3.1 mmHg, p=0.6), pre-surgery washout diurnal IOP (25.5 ± 3.0 vs 25.4 ± 2.9 mmHg, p=0.9) and visual field mean deviation (-3.61 ± 2.49 dB vs -3.61 ± 2.60 dB, p=1.0). At 4 years, the proportion of eyes requiring no medications was significantly higher in the HS group (65% vs. 41%, p<0.001) and the mean unmedicated IOP was lower in the HS group (16.7 vs 17.3). There was a significant reduction in the cumulative risk of incisional glaucoma surgery at 4 years (1.9% vs. 6.9%, Hazard Ratio = 0.25, p=0.013, logrank p=0.007). From 2 to 4 years, mean central endothelial cell count fell by 3% in the HS group (2060±480 HS vs. 2014± 502, p=0.9) and 2% in the CS group (2183±425 vs. 2144±420, p=0.9). There were no significant differences in other adverse events at 4 years compared to 2 years.


Hydrus microstent combined with phacoemulsification results in sustained IOP and medication reduction for up to 4 years postoperatively with no significant loss of effect between postoperative years 2 and 4. The treatment arm showed a significant reduction in subsequent glaucoma surgery (trabeculectomy / tube shunt) despite similar IOPs. The limitations of medical therapy (non-compliance, circadian IOP fluctuation) are well documented and a possible contributing factor to the difference in secondary surgery rates. There were safety issues. Addition of a Hydrus Microstent to cataract surgery significantly lowered the risk of needing subsequent incisional glaucoma surgery.

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