iStent | The world’s smallest implantable device offers huge potential benefits for people with glaucoma.
The hallmark of the disease is progressive damage to the optic nerve, related to a buildup of pressure within the eye, that deteriorates vision and can lead to blindness. The standard therapies are eye drops, laser treatment, or surgery to either reduce fluid production or increase outflow. A new alternative, now being used at University of Colorado Hospital, is the iStent, a tiny titanium device that acts like a miniature drainage system for built-up fluid.
The Food and Drug Administration approved the device in June 2012 for people with mild to moderate glaucoma who undergo cataract surgery.
The idea behind the iStent implant is to establish a permanent fluid outflow route in the eye. In people with normal vision, fluid drains from the eye through a lattice of collagen and cells, known as the trabecular meshwork, that forms a narrow space between the iris and the cornea. A conduit called Schlemm’s canal takes the fluid out of the eye and into the bloodstream.
But in people wtih glaucoma, blockages in the meshwork prevent fluid from reaching the canal. The 1-millimenter-long iStent rides the tip of a preloaded delivery device. Surgeons insert the drain-like device through the trabecular meshwork, then insert it into Schlemm’s canal. Once they have it positioned and seated it, they release the iStent with a push of a button, providing a path through which fluid can drain.
Don Tomlinson, 77, of Brighton, was diagnosed with glaucoma 12 years ago. He received an iStent in his left eye at UCH about a month ago as part of his cataract surgery and will get one in the other eye later this month. He said he’s not aware there is an implant in his eye.
“It’s very comfortable,” he said. “I felt nothing different. Wearing a patch after the surgery was more of a problem than anything else.” Leonard Seibold, MD, an ophthalmologist with the Eye Center at UCH, has done seven iStent procedures since last November – including the procedure on Tomlinson – with good results. The outpatient procedure adds just a few minutes to cataract surgery already being performed and requires no additional cutting, he said. Patients’ vision improves the day after surgery and they need only mild restrictions for about a week.
“It’s not a cure,” he said, “but it is very efficient at reducing the amount of medications needed.”
That’s an important benefit, Seibold explained, because glaucoma patients often use one or more pressure-reducing eye drops two or three times a day. If they don’t take them regularly, the pressure worsens. But for some patients, the drops cause dryness, burning, redness and inflammation, he said.
“If a patient can stop one or two medications with the same level of eye pressure, that’s a big improvement,” Seibold said. Tomlinson said he stopped taking medications altogether for about three weeks after his surgery. After a recent slight rise in pressure, he’s now putting one drop a day in each eye.
The minimally invasive procedure also avoids the risks of traditional glaucoma surgery, which creates entirely new openings to bypass blocked drains and improve fluid outflow, Seibold noted. The Eye Center now resorts to traditional surgery only in advanced cases, he added.
“It’s more invasive,” he said. “We typically use it only in advanced cases because of the serious risks associated with it. We’re also at the mercy of how the eye heals.” The iStent procedure, by contrast, leaves the outer tissue of the eye untouched and produces no scarring, he said.
The Centers for Medicare and Medicaid Services okayed coverage of the iStent early this year. Aetna is among commercial payers that cover it when medications fail to control intraocular pressure. The FDA approved one implant in each eye, Seibold said, but in Canada surgeons have been experimenting with implanting two or more devices in different quadrants of the eye with promising results
The Eye Center has begun sending out notices to referring opticians and ophthalmologists to let them know the iStent is available, Seibold said.
“We think there is a bigger pool of potential patients for the procedure,” he said.
Tomlinson, who said he’s tried various medications to treat his glaucoma over the years, said he sees little risk and plenty of potential upside in the iStent treatment.
“There is a strong possibility it will help reduce the pressure on the optic nerves or at least maintain the pressure I’ve got,” he said. “If it doesn’t do anything at all, I’ll still have the standard treatment methods.”