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Take-home: With the approval of a new surgical device aimed at lowering IOP, surgeons explore benefits of micro-stent implantation.
Atlanta-A micro invasive glaucoma surgical (MIGS) device (CyPass Micro-Stent, Alcon) can safely lower IOP in patients with glaucoma for at least 2 years, researchers said.
“The MIGS devices are a breakthrough in glaucoma therapy and this is another step down the road,” said Reay Brown, MD, Atlanta Ophthalmology Associates, Atlanta.
Dr. Brown is a co-author on a paper describing the 2-year data from the COMPASS trial of the micro-stent that was published in Ophthalmology.
The FDA approved the micro-stent earlier this year for treatment of mild to moderate primary open-angle glaucoma (POAG) in conjunction with cataract surgery. It is the first direct competitor to a previous stent (iStent Trabecular Micro-Bypass Stent, (Glaukos), which the FDA approved 4 years ago for the same indication.
MIGS devices offer an advantage over ocular hypotensive medication, tube shunts, and trabeculectomy for POAG, Dr. Brown said. Unlike eye drops, they do not depend on patients to apply them regularly. The procedure to implant MIGS is shorter and as of now, complications appear much less common than with trabeculectomy and tube shunts.
“The iStent has already shown the way, and we’ll see how the CyPass fits in,” said Dr. Brown. “In my practice, I do an iStent on anybody who is having cataract surgery and is being treated for glaucoma.”
In contrast to the iStent, which creates a bypass through the trabecular meshwork, the CyPass is implanted in the supraciliary space. “It’s good to have options,” said Dr. Brown.
The CyPass measures 6.35 mm in length with a 510 µm external diameter. Surgeons implant the device with an applier using direct gonioscopy in a procedure initiated by a bluntly dissected plane between the ciliary body and the sclera.
Composed of polyimide material, the device assumes the curvature of the applier guidewire to follow the sclera contour along the supraciliary space. Once retention features are engaged, the surgeon retracts the guidewire and withdraw the applier. The micro-stent remains in place indefinitely.
To test the effectiveness of the recently approved device, Dr. Brown and his colleagues recruited 897 people with POAG and cataracts, of whom 505 enrolled in the study. Their mean age was 70 years. Fifty-three percent were women and 84% were white. Their mean best corrected visual acuity was 20/67 Snellen equivalents. Their visual field mean deviation was -3.47 D. Their diurnal mean unmedicated IOP was 24.4 mm Hg.
None of the patients were taking more than 3 ocular hypotensive medications, but 82% were taking more than 1. None had significant risk associated with ocular hypotensive medication washout, previous corneal or glaucoma surgery, clinically significant ocular pathology other than glaucoma and cataract, acute angle closure, or traumatic, congenital, malignant, uveitic, pseudoexfoliative, pigmentary, or neovascular glaucoma.
The researchers randomly assigned 374 of the 505 subjects to undergo cataract surgery with subsequent implantation of the device in one eye. Another 131 got only cataract surgery in the study eye. There were no statistically significant differences between the 2 groups in demographics or baseline ocular parameters.
After 24 months, 480 patients remained in the study. Of those who received the device, 77% achieved more than a 20% reduction in unmedicated diurnal IOP, compared to 60% of those who had cataract surgery alone, a statistically significant result ( p = 0.001).
Similarly, the mean unmedicated IOP at 24 months was 17.0 mm Hg in the patients who had the device implanted and 19.3 mm Hg in the patients who only had cataract surgery ( p < 0.001).
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The device also reduced the use of ocular hypotensive medication. Patients implanted with the device went from a mean of 1.4 to 0.2 drugs in the first year, and stayed at that number through the second year. Patients who only had cataract surgery went from a mean of 1.3 drugs at baseline to 0.7 at 12 months and 0.6 at 24 months ( p < 0.001).
“We know that compliance is a terrible problem for glaucoma patients,” Dr. Brown said, “so anything we can do to lower the pressure with a surgical device is going to be important.”
More than 98% of subjects in both groups achieved a 20/40 or better best corrected visual acuity through 24 months. Eight percent of the micro-stent group experienced a loss of 10 letters or more, compared to 15.3% of the control group.
However, this loss of acuity was transient for most. At 24 months, only 1.1% of patient in the device group and none of the cataract-only patients ended up with more than 2 lines below their baseline level.
Patients implanted with the micro-stent experienced a higher rate of other adverse events as well, including iritis and secondary ocular surgical intervention, but the differences between the groups were not statistically significant for any of these.
Dr. Brown surgically placed his last micro-stent 3 years ago when the clinical trial concluded. “I have found it to be very good,” he said. “It’s not difficult to implant. I did not have any complications implanting it and I have found it to be effective in lowering IOP.”
Some of his patients have had the device for as long as 4 years. “The devices have been stable and have not changed position or caused any problems later,” he said. “They have continued to be helpful in lowering pressure.”
While the iStent and CyPass are both currently approved only for use at the time of a cataract procedure, they might ultimately be used in patients without cataracts, Dr. Brown said.
“At some point, glaucoma will become a surgical disease, meaning the first therapy will be a surgical intervention,” he said.
It is not clear whether the CyPass and iStent might have advantages in different patients, Dr. Brown said. “We’ll just have to see which is the most effective and which is the safest,” he concluded. “And it’s possible they might be used together.”
This article was adapted from Dr. Brown’s presentation at the 2016 annual meeting of the American Society of Cataract and Refractive Surgery.