Award-winning cataract and glaucoma ophthalmologist, Dr Andrew Tatham, has visited Australia from Scotland, to discuss his experience with the Hydrus microstent – a minimally invasive glaucoma surgery (MIGS) device for adult patients with open angle glaucoma.
At a series of dinner lectures hosted by Alcon, Dr Tatham and Associate Professor Ashish Agar from Marsden Eye Specialists in Sydney, described the clinical evidence and meta-analysis that support the use of the Hydrus, and shared their tips for achieving the most successful patient outcomes.
Dr Tatham said an important outcome from a clinical perspective is to lower intraocular pressure (IOP), however from the patient perspective the most important outcome is “most definitely” to reduce the need for medication (eye drops) and minimise the risk of requiring invasive surgery.
He said the five-year evidence suggests that in conjunction with cataract surgery, the Hydrus achieves all of this for the majority of patients.
Not Just A Bypass
The Hydrus microstent is distributed by Alcon, which inherited the technology with the acquisition of Ivantis in early 2022.
Dr Tatham explained that this MIGS device bypasses the trabecular meshwork and helps open and scaffold Schlemm’s Canal. Spanning over 90°, it allows access to many collector channels in the inferior nasal system, which he believes enables it to achieve better efficacy than other MIGS devices “because it is not just bypassing the trabecular meshwork”.
When implanted, the device restores flow of aqueous from the anterior chamber through the inlet of the microstent into Schlemm’s canal.
Easier Than You Think
Dr Tatham told ophthalmologists that inserting the device, is “a lot easier than you might think” and “a lot easier than doing a phaco”.
Using a gonio prism, the Hydrus microstent is inserted through a clear corneal incision and guided through the trabecular meshwork into Schlemm’s canal. Dr Tatham said the procedure is “much like inserting a cannula – it (the Hydrus) goes in nicely – there is no resistance whatsoever”.
However, he cautioned, “you need to get the positioning right – this is critical – it is really important to get good visualisation, which requires the tilt of the patient’s head and the operating microscope”.
This was a point that Assoc Prof Agar reinforced in his subsequent presentation.
Assoc Prof Agar, who regularly performs cataract and glaucoma procedures for patients in far west New South Wales, said the Hydrus Microstent had “changed the game” for eye care in the outback, enabling IOP to be controlled in a safe way.
Describing it as “a delivery system that makes life so much easier”, he said the key is to get the patient’s position correct to optimise visualisation. “It’s a very forgiving technique… it really is a resistance-free procedure.”
Supporting Studies
Dr Tatham said by providing “access to as many of the collector channels as possible” and keeping the canal open, the flow of aqueous from the anterior chamber into Schlemm’s canal is optimised.
“Outflow studies support this reasoning,” he said, highlighting a study that found one Hydrus increased outflow by 73% compared with 34% when two iStents were implanted.
“That (result) will vary, depending on whether you get the iStent to connect to a patient collector channel or not,” he added.
The key study for the Hydrus has been the HORIZON study – the largest MIGS study with the longest follow-up (five years) to date.1
HORIZON included 566 patients at 38 centres from across nine countries, with patients randomised to Hydrus plus phaco or phaco alone.
“A really important part of this study was that they washed out the medications – so medications were stopped at baseline and at key endpoints to take away the ‘muddling effect’ of medications to see the power of the device on its own,” Dr Tatham explained.
The study aim was to determine what proportion of patients had a 20% reduction in pressure after two years.
Dr Tatham said the study found 77% of patients who had phaco plus Hydrus had a reduction in pressure of 20% or more at two years. The absolute change in pressure at two years was 7.6mmhg – significantly more than the phaco alone group.
“Phaco alone patients also had a reduction, but it was a significantly more powerful pressure reduction when combined with the Hydrus,” he observed.
However, he said, “patients don’t really care about pressure reduction – what they care about is the ability to stop their drops”.
HORIZON found that 66% of Hydrus patients remained medication free at five years, and for those who were only using one drop at baseline, the results were even more impressive, with 73% not requiring drops five years later.
Additionally, there was more than 50% relative reduction in incisional secondary surgical intervention.
Dr Tatham told the audience that HORIZON findings on safety were “very reassuring”, with the main problem being hyphemia, which can obscure the surgeon’s view. This was found to occur in 11% of patients and can be managed (Dr Tatham showed a video to explain how he does this).
Further support for the Hydrus, he said, has come from the Cochrane Group, which is famous for “really good quality meta-analysis and for being quite conservative in their recommendations – they’ll often say, ‘there isn’t sufficient evidence’”.
He said the Cochrane Group found moderate certainty of evidence that a reasonable proportion of people with cataracts and mild-to-moderate glaucoma, treated with Hydrus plus phaco and phaco alone, will not require medication. “They also say there is moderate certainty of evidence that Hydrus is more effective than the iStent, at least in the short term (two years).”
Dr Tatham said network meta-analysis, which compares different devices head-to-head, also found favourable evidence to support less risk of the need for medication for patients implanted with the Hydrus.
He concluded by stating that “we have evidence for the first time now that MIGS might reduce the risk of needing subsequent surgical intervention” as well as the ability to control IOP, reduce medications, manage ocular surface disease, reduce the risk of progression, and address poor adherence.
He said, “it is a missed opportunity if you don’t reduce pressure when doing cataract surgery”.
Reference
1. Ahmed, I.I.K., De Francesco, T., Rhee, D., et al., HORIZON Investigators. Long-term outcomes from the HORIZON randomized trial for a Schlemm’s canal microstent in combination cataract and glaucoma surgery. Ophthalmology. 2022 Jul;129(7):742-751. doi: 10.1016/j.ophtha.2022.02.021. Epub 2022 Feb 23. PMID: 35218867.
