Hydrus®: The Long-Term Evidence

*Paid Alcon Consultant

Presenting at Alcon’s Hydrus symposium at the European Glaucoma Society Congress in Dublin (June 1-4, 2024), Gus Gazzard – Professor of Ophthalmology at UCL & Director of Glaucoma Service, Moorfields Eye Hospital, London – detailed the results of the 5-year HORIZON study: “the largest prospective pivotal randomized control trial for a MIGS device to date” (1).

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HORIZON – a large, multicentre randomized controlled trial designed to evaluate the safety and efficacy of the Hydrus® Microstent – saw 80% of patients complete a full five-year follow-up. “This wasn’t simply a retrospective check-in years later,” Professor Gazzard explained. “It was a planned prospective follow up; these are patients that continued to be monitored.” As such, Gazzard went on, the study has yielded “reliability and robustness of data, and – for a surgical trial – a staggeringly impressive rate of patient retention.”

Gazzard noted that the Hydrus has been shown to reduce intraocular pressure (IOP) and reduce medication usage when used in combination with cataract surgery at 24 months in patients who have had washed out IOP measurements (1-4). Illustrating the HORIZON finding that 77.2% of Hydrus patients achieved an unmedicated IOP reduction of >/= 20% from baseline at 24 months(4)^a Gazzard explained that there were no concurrent medications confounding the results. He added that the HORIZON trial design, which involved washing out medications before measuring IOP, meant that the results represented a true effect of the surgical intervention rather than an inflated outcome from medication use.

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Why long-term data matters

Turning to the importance of the longer-term follow-up, Gazzard argued, “We should be asking all our device studies, whether of lasers or MIGS, to continue out to at least five or more years.” The five-year data showed that a significant proportion (59%) of Hydrus patients remained entirely medication-free (4).^b This is one of the statistics I reach for when patients are saying, ‘Is it worth me having a Hydrus?’” noted Gazzard.

As expected, more patients who had fewer glaucoma drops at the beginning of the HORIZON trial (66%) remained medication-free at five years.^c "Clearly, if you require three medications to get your pressure under control when you enter a study, you're less likely to be completely free of medication,” Gazzard explained.

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Immediate postoperative safety

Another advantage Gazzard emphasized was Hydrus’s role in reducing day-one postoperative IOP spikes (1.4% rate of IOP > 40 mmHg on post-op day 1 among Hydrus patients versus 14.4% among CS-only patients)^d – a risk that is often overlooked. In many European countries, he noted, patients are not routinely checked on the first postoperative day, meaning these spikes can go unnoticed.

“It’s very reassuring to know that the Hydrus reduces these day-one postoperative IOP spikes in a very large proportion of patients,” he continued. For some patients with brittle, advanced disease, the margin of safety could be crucial.

Reducing future surgery

The HORIZON study also demonstrated a significant reduction in the proportion of patients needing later incisional glaucoma surgery,^e Gazzard explained. While he said this doesn’t amount to a “get out of jail free card,” he noted that the difference between the control and treatment groups was meaningful, with fewer patients in the cataract surgery with Hydrus® Microstent (CS-HMS) group requiring further surgery over five years. These surgical decisions were reviewed by a masked panel of glaucoma specialists, including Gazzard himself, ensuring that judgments were unbiased.

In translating these findings to daily practice, Gazzard said he tells Hydrus implant patients: “While this doesn’t guarantee that you won’t need surgery, there’s a chance that you might not if we do this.” Additionally, he explained that combining Hydrus implantation with cataract extraction means that if a patient later needs trabeculectomy, they would be pseudophakic.

_{[a] n=369 eyes receiving Hydrus Microstent + cataract surgery
[b] vs. 35.8% of eyes in the control group of a 5-year pivotal trial follow-up: Hydrus Microstent + cataract surgery (n=308 eyes) vs. cataract surgery alone (n=134 eyes); p<0.001.
[c] Patients previously on 1 medication: Hydrus Microstent + cataract surgery (n=308 patients) vs. cataract surgery alone (n=134 patients); 41.1% of the cataract surgery-alone patients remained drop-free.
[d] 2-year pivotal trial: Hydrus Microstent + cataract surgery (n=369 eyes) vs. cataract surgery alone (n=187 eyes). IOP > 40 mmHg was 14.4% in cataract surgery alone group .
[e] Secondary Surgical Interventions (SSI) include trabeculectomy, tube shunt, gel stent, ECP/TSCP, non-penetrating; (9/369 Hydrus Microstent +cataract surgery and 10/187 cataract surgery); vs. cataract surgery alone: 2.4% in Hydrus + cataract surgery vs. 5.3% in cataract surgery only}

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