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Researchers look at customizing number of iStents according to patient needs
Results of implantation of multiple trabecular micro-bypass stents were presented at the American Glaucoma Society meeting.
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Implanting one iStent can significantly reduce IOP in cases of open-angle glaucoma; adding a second or third trabecular micro-bypass stent can further reduce IOP, according to a poster presentation at the American Glaucoma Society annual meeting.
This study was the first comparative control study using a dose-response surgical trial in the development of this theoretical basis for trabecular bypass titratable therapy, L. Jay Katz, MD, told Ocular Surgery News.
L. Jay Katz
“The study evaluated the efficacy of multi-stent treatment as a titratable therapy to customize patient treatment and reach ever-lower patient target pressures based upon OAG severity and/or progression,” Katz said. “In doing so, the study validated the future role and promise of multi-stent injectable therapy in a pre-loaded device such as iStent inject (Glaukos).”
Study methods
The MIGS Study Group evaluated patients with IOP ranging from 18 mm Hg to 30 mm Hg who had open-angle glaucoma that was not controlled on one to three medications. Unmedicated IOP after preoperative washout in these patients was 22 mm Hg to 38 mm Hg. Patients were randomized to receive one, two or three stents.
Five-year follow-up is planned, with 119 patients in the prospective study having been followed for 18 months, according to the poster.
Study results
Before washout, mean IOP was 19.8 mm Hg, 20.1 mm Hg and 20.4 mm Hg in patients who would receive one, two and three stents, respectively. After medication washout, mean IOP was 25 mm Hg, 25 mm Hg and 24.9 mm Hg in those patient groups. At 18 months postoperatively, the mean unmedicated IOP decreased to 15.6 mm Hg, 13.9 mm Hg and 12.3 mm Hg, respectively. Higher proportions of multiple-stent eyes had an IOP reduction of 40% or more with IOP less than 15 mm Hg compared with single-stent eyes, according to the poster.
“The current study and several other independent prospective clinical studies demonstrate that two trabecular bypass stents provide significant IOP reductions and post-treatment mean baseline pressures that are routinely less than 15 mm Hg. The National Eye Institute-sponsored AGIS study confirmed that achieving postoperative mean baseline pressures under 15 mm Hg resulted in a significant reduction/elimination of further progressive glaucomatous damage in OAG patients,” Katz said.
Of 119 eyes, five had best corrected visual acuity loss due to cataract progression in the 18-month follow-up period. Katz reported no other significant complications; there was typical intraoperative transient bleeding at stent placement.
“The iStent inject, preloaded with two trabecular bypass stents, is designed to optimize patient IOP reductions with minimal disruption to the ocular anatomy,” Katz said.
If severe conditions require additional IOP reduction after stent implantation, Katz recommended that surgeons enhance therapy by prescribing topical glaucoma medications.
FDA approval and commercialization of the iStent inject are the next steps in using multiple stents as a primary method in micro-bypass glaucoma surgery, he said.
Cost
The estimated future costs of iStent inject therapy may be lower than long-term topical drug therapy, with additional improvement in costs associated with patient vision loss and/or blindness due to noncompliance, Katz said.
Currently, the FDA has approved only one iStent implantation in conjunction with cataract surgery. Therefore, few if any payers would reimburse for multiple stents, and additional costs currently would fall on the patient, Katz said.
“The study endpoints were not designed to evaluate costs; however, with corresponding reductions in drug burden and chronic medication costs, as well as reduced dissatisfaction/compliance issues with the medications themselves, the benefits are promising,” he said. – by Kristie L. Kahl
For more information:
L. Jay Katz, MD, can be reached at Wills Eye Hospital Glaucoma Service, 840 Walnut St., Philadelphia, PA 19107; email: ljkatz@willseye.org.Disclosure: Katz reports he is compensated as a medical monitor and member of the scientific advisory board for Glaukos.