Breaking Through Misconceptions About Standalone Treatment of Glaucoma
A recent study demonstrated that iStent infinite standalone surgery can achieve a clinically significant reduction in intraocular pressure (IOP) in patients with open angle glaucoma (OAG) uncontrolled by prior therapy.
Lead author, Steven R. Sarkisian, Jr., MD said the results of this prospective, multi-center, pivotal study have left many astonished.
“This new data blows up previous misconceptions about trabecular micro-bypass surgery and directly challenges the referral biases of glaucoma specialists who say, ‘I just don’t see the types of patients where I could use this technology’,” he said. “Many glaucoma specialists used the early and more limited evidence about the original iStent to extrapolate their own predispositions about trabecular micro-bypass, but the pivotal trial data for the iStent infinite turns that all on its head.”
Study Design and Results
The study enrolled 72 eyes of 72 patients, with a mean age of 71.9 years and a preoperative medicated mean diurnal intraocular pressure (MDIOP) of 23.4±2.8 mmHg on a mean of 3.1±0.9 IOP-lowering medication classes. Of those enrolled, 61 eyes had failed prior surgeries (Failed-Surgery subgroup), while 11 eyes were uncontrolled on maximum tolerated medical therapy (MTMT subgroup).
The study’s effectiveness endpoints were the proportion of eyes achieving ≥20% MDIOP reduction from baseline at month 12 on the same or fewer intraocular pressure (IOP)-lowering medication classes (responder endpoint) and the mean change in MDIOP from baseline at month 12.
Results showed that 76.1% of all enrolled patients met the responder endpoint, with a mean reduction (SE) in MDIOP at month 12 of 5.9(0.6) mmHg [5.5(0.7) mmHg Failed-Surgery subgroup, 8.1(0.9) mmHg MTMT subgroup]. For patients on the same or fewer medication(s) as baseline, 53.0% achieved ≥30% MDIOP reduction without additional surgical interventions or other events.
New System Design
The infinite system is designed with 3 wide flange stents designed to be implanted two o’clock hours apart, which provides up to 240° of outflow coverage. A study by Katz et al, established that 2 stents are more efficacious than 1, and 3 stents are more efficacious than 2.
The iStent infinite keeps the same wide flange as the current iStent inject W and is designed to pivot in the eye more effectively to facilitate visualization and implantation of three stents 2 o’clock hours apart from each other. The new injector system will allow an unlimited number of delivery attempts, compared to the 4 attempts available with the iStent inject W.
A Different Approach to MIGS Patient Populations
One crucial aspect of the study is that it included patients that have not been historically thought of as being good patients for trabecular micro-bypass surgery, including those that had a prior failed trabeculectomy or failed tube shunt.
Some surgeons believe that once the trabecular meshwork is bypassed with a trabeculectomy that procedures such as SLT or canal-based MIGS are not going to be effective. “The pivotal trial demonstrated quite the opposite is true. We saw tremendous response to iStent infinite trabecular micro-bypass in these refractory patients.”
Another distinction in the study population is that patients in the failed surgery group had more than 2 failed prior surgeries and had a mean medication burden of 3.
Dr. Sarkisian said that several of his patients that participated in the study had a history of a failed ExPress Shunt, a failed tube shunt, multiple sessions of laser trabeculoplasty, and/or were on multiple medications with a pressure in the mid-twenties. After having the iStent infinite procedure, those patients had pressures down into the mid-teens and were on fewer medications, without a washout period.
Overcoming Biases
Dr. Sarkisian urges people to stop using the words “severe” glaucoma and “refractory” glaucoma interchangeably. A patient with no visual field loss or very mild visual field loss, with an elevated IOP, maximally tolerated medical therapy, phakic or pseudophakic, with failed prior surgical therapy, is an excellent candidate for the iStent infinite, he said. “I think we demonstrated in the study that any patient with mild to severe glaucoma can be refractory, and an iStent infinite is an option to be considered.”
Dr. Sarkisian pointed out that due to the original iStent study design, with one stent combined with cataract surgery in people that had mild to moderate glaucoma who had never undergone any other intervention, that many glaucoma specialists were automatically biased against the iStent as a standalone procedure or in more refractory glaucoma.
“This left the impression that only the mild to moderate and medically controlled patient population was acceptable for iStents,” he said. “We now have the highest level of data obtained through a controlled pivotal study, proving that iStent infinite can be highly effective independent of cataract surgery, including in tough to treat patients.”
Disrupting the Glaucoma Treatment Algorithm
The iStent infinite has the potential to be a major disruptor in the glaucoma treatment algorithm. Currently we have no standalone MIGS procedure with this level of safety and efficacy. The iStent infinite can now be considered the first or second line treatment as well as after a failed trabeculectomy, tube shunt, or even a cycloablative procedure.
“This is disruptive because it is not the way people have been thinking. Not only is it probably a better therapy, it is going to be safer and with less hyphema than all of the canal dilating/cutting procedures currently available,” he said. “iStent infinite is a welcomed addition to the armamentarium of options to safely and effectively manage my patients with glaucoma.”
