Insight News article, October 2024
Glaukos has made significant modifications to its iStent platform that Australian surgeons, with early access to the MIGS technology, say is improving the surgical experience with the potential for better patient outcomes.
For Dr Colin Clement there is much to like about the new iStent infinite. After receiving TGA approval in Australia earlier in 2024, headlines for the latest minimally invasive glaucoma surgery (MIGS) device from Glaukos have emphasised the new three-stent approach – upgraded from two – and the unlimited number of delivery attempts – upgraded from four.
He agrees these mark a significant step-change from older generation iStents, but his standout feature is the new levels of visualisation during surgery, an important factor considering he’s implanting the world’s smallest known medical device at 0.36 x 0.36 mm.
What Dr Clement is referring to is a clever design tweak incorporating ‘viewing windows’ on the insertion tube, so surgeons can visualise stent positioning. Essentially each modification that’s culminated in the iStent infinite has involved the injector handpiece.
“Visibility of the trocar – the small needle used to place the stents into the target tissue – has been one of the biggest improvements for me,” says the Sydney-based cataract and glaucoma subspecialist.
“The stents slide along this component into the point of insertion. With the previous injector, sometimes it was difficult to accurately see where that’s positioned in the eye. Now, it’s clear as day, which is vital when you consider that 90% of a successful implantation comes down to visibility.”
Glaukos helped create the MIGS category in the early 2010s with its first generation iStent, and Dr Clement has been an early adopter at each step.
The stents are implanted in the Schlemm’s canal, the eye’s primary drainage channel, and work to lower intraocular pressure (IOP) by restoring the natural, physiological outflow of aqueous humor. It has proven to be an ideal intermediate therapy where other options, such as eye drops, have failed for glaucoma patients also wanting to avoid more invasive options like tube shunts and trabeculectomy.
Dr Clement remembers the 2016 second generation iStent inject being a major step forward. At a third of the size of the original device, it also created a new standard of care using two stents in a pre-loaded injector. Glaukos then developed the iStent inject W with a wider flange at its base to optimise stent visualisation and prevent over-implantation, while also making modifications to the handpiece to offer more consistent injection speeds.
But with the new iStent infinite, he says Glaukos has made the surgical experience even simpler, with the added potential of greater IOP reductions in some cases. This is because the iStent infinite comes with an extra heparin-coated titanium stent, with all three stents preloaded into the newly designed auto-injection system.
According to the company, this allows the surgeon to inject stents across a span of up to approximately six clock hours around Schlemm’s canal, with the intention to reduce IOP in adult patients with primary open-angle glaucoma (POAG) currently treated with ocular hypotensive medication.
“This increases your chances of getting the stent in the location you need and hitting the pressure reduction and medication reduction you’re targeting,” Dr Clement says.
“We’ve been conducting an Australian multi-site clinical trial for the past two years looking at the outcomes of three stents in eyes combined with cataract surgery and standalone. Those with cataract surgery are getting similar outcomes to those with two stents implanted, but those who had standalone with three stents seem to be doing better than those with two stents.”
Dr Clement plans to publish that data in 2025/26, but in the US a 12-month pivotal trial for iStent infinite (standalone) was conducted in patients with open-angle glaucoma with failed prior surgical intervention.1
Notably, those enrolled had a significantly higher preoperative treatment burden with more severe glaucoma compared with other trabecular bypass MIGS pivotal trials,1,2,3 Glaukos says.
Despite this tough-to-treat population, the iStent infinite “delivered exceptional results”, demonstrating sustained efficacy throughout the course of the study.1 It found 73.5% of patients had ≥20% reduction in IOP, and 47.3% had a ≥30% reduction. And 91.7% of study participants in the failed prior surgery group reduced or maintained medication burden at 12 months.1 There was also a 16.9 mmHg mean diurnal IOP in patients who did not have an IOP-related secondary surgical intervention (SSI, n=57), corresponding to a mean reduction of 6.5 mmHg (27.7%).4
In other major upgrades to the iStent infinite, Glaukos has incorporated a stent delivery button designed for smooth stent deployment with an unlimited number of delivery attempts. This is a significant advance over the previous injector that only allowed four.
With around 20% of his cases previously involving an under- or over-implantation, Dr Clement says having unlimited delivery attempts improves surgical accuracy and efficiency. It’s also a cost-saver, avoiding the need to discard the system once reaching the four-attempt limit.
“If you under-implant the iStent infinite, it’s not a big deal to reload the stent and have another attempt until you get it positioned correctly,” he says.
“Other changes to greatly improve the surgical experience include a slight angulation on the handpiece, making the angular approach better and allowing you to access a wider area of tissue without causing significant distortion to the eye.”
Glaukos says this eight-degree angled insertion tube is designed to minimise incision interference and provide greater access to deliver stents widely.
“There’s also a new auto-retracting introducer tip that removes a manual step we had to do with previous generations,” Dr Clement adds.
The resurgence of glaucoma
For Western Australia’s Dr Lourens van Zyl, the MIGS category – spearheaded by the iStent and Hydrus microstent and the elegance of these surgeries – hasn’t only made glaucoma a more attractive subspeciality but has opened surgical glaucoma management to general ophthalmologists.
Although the Perth-based ophthalmologist has completed a glaucoma fellowship, today at Crystal Eye & Laser Centre he divides his time between refractive laser surgery and general ophthalmology that includes some glaucoma work.
“The beauty of stent-based MIGS is that ophthalmologists that aren’t fully dedicated to glaucoma can now do glaucoma surgeries as routine, and you don’t have to necessarily send patients to a glaucoma subspecialist and create a double referral,” he says.
“It’s making glaucoma management, or surgical glaucoma management, so much more accessible, and with the iStent infinite, Glaukos has improved on the original design significantly. It’s made this surgery so much easier.”
Dr van Zyl was WA’s first to implant the iStent infinite and, like Dr Clement, was impressed with the new-found visibility mid-surgery.
“In the first case performing the iStent infinite, the patient’s Schlemm’s canal and angle was difficult to see, but I was able to visualise the tip much better and use the landmarks and, even though this was my first case, I managed to implanted it perfectly,” he says.
“We have to wait for the outcomes, but with the ease-of-use, I think this is probably going to be the more standard MIGS to use.”
Equal access
Glaukos’ iStent technology has approved indications for use in combination with cataract surgery or as a standalone procedure and is reimbursed by private health funds for those who are privately insured. Many public and teaching hospitals around the country have also approved the use of the technology and have made MIGS available in the public sector.
For the iStent infinite, Glaukos has secured reimbursement and it’s covered by private health insurance.
Dr Clement says it’s vital to offer a proven option for patients who either don’t have cataracts or who have previously had cataract surgery, but more work is required to better identify patients who would benefit from standalone MIGS.
“Having said that, I have had some patients that have had incredible results with a standalone iStent,” he says.
“MIGS is not a first-line treatment at the moment, and the reimbursement codes state that clearly. Certainly, in any patient with treated glaucoma that requires a cataract operation, I will always consider MIGS in combination. For standalone, that group is mixed; the indications are: intolerant of their current treatments, trying to avoid filtration surgery or previous failed other interventions, and there’s a range of severity from mild to severe glaucoma.”
For Dr van Zyl, greater use of MIGS and selective laser trabeculoplasty (SLT) have decimated his trabeculectomy rate and helped his patients avoid invasive surgeries. But being able to fix a patient’s vision with cataract surgery while easing their medication burden with MIGS in the same surgical sitting is a “double whammy” that’s a fantastic practice builder.
“It’s massive because we have an option for patients who are pseudophakic, on one eye drop, or with some high pressure but no signs of glaucoma. Surgery has its risks, but the surgery itself is so straightforward and safe because you’re hardly taking any tissue out,” he says.
In fact, iStent infinite occupies 3% of the Schlemm’s canal, leaving 97% untouched.
“It’s something extra we can offer patients, especially those unhappy with using drops – it significantly reduces disease morbidity,” he says. “I’m selective with who this is offered to, I have probably gotten 60-70% of patients off eye drops with standalone MIGS.”
For the references and image find ther full article here.