Schlemm canal scaffold results ‘encouraging’

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Two-year follow-up data is positive for eyes enrolled in the first study of the Schlemm canal scaffold (Hydrus, Ivantis).

Dr. Samuelson

By Cheryl Guttman Krader; Reviewed by Thomas W. Samuelson, MD

Minneapolis-Results from 2 years of follow-up from a first pilot trial show that implantation of a Schlemm canal scaffold (Hydrus, Ivantis)-alone or combined with cataract surgery-results in significant and durable reductions in IOP and medication use in eyes with mild to moderate glaucoma.

“The Hydrus I trial has the longest follow-up of all Hydrus trials to date, and the results are very encouraging,” said Thomas W. Samuelson, MD, medical monitor for the non-comparative, multicenter European study.

Summarizing the outcomes, Dr. Samuelson noted that combining phacoemulsification with the Schlemm canal scaffold conferred greater reduction in IOP compared with the device alone, which was not surprising. However, he emphasized that the more modest reduction in IOP with the glaucoma procedure alone was still accompanied by a significant, 70% reduction in medication use.

Safety data showed adverse events were few, did not increase over time, and did not include any serious complications, such as hypotony, corneal decompensation, and endophthalmitis. In addition, there were no cases of device migration or perforation.

“The pivotal randomized U.S. trial comparing implantation of the Schlemm canal scaffold plus phacoemulsification versus phacoemulsification alone is now under way, and there are three other manufacturer-sponsored trials ongoing in Europe, including two using the microbypass trabecular stent (iStent, Glaukos) as an active comparator,” said Dr. Samuelson, adjunct associate professor of ophthalmology, University of Minnesota, Minneapolis, and attending surgeon, Minnesota Eye Consultants, Minneapolis.

The scaffold is an 8-mm long device made of flexible nitinol that is placed via an ab interno approach.

“It not only enters and resides within the canal, like the microbypass trabecular stent, but it provides tension on the inner wall to keep the canal open,” Dr. Samuelson said. “Studies by Carol Toris have shown this effect improves outflow facility.  The device is easily inserted through a 1.5 mm incision, and with this procedure, surgeons can be certain that the device resides in the canal where it should.”

Patient enrollment

Hydrus I enrolled a total of 69 patients, including 40 who received the scaffold alone and 29 who underwent a combined procedure. Eligible patients were required to have a glaucomatous optic nerve defect and no more than –12 dB of visual field loss. Eyes with pigmentary or pseudoexfoliation glaucoma were allowed, but the majority (~85%) had primary open-angle glaucoma. Pseudophakic patients were eligible and represented 31% of the scaffold-only group.

Patients with uveitic or neovascular glaucoma as well as those with prior glaucoma surgery, including argon laser trabeculoplasty, were excluded as were patients with any significant ocular pathology other than glaucoma or cataract.

Baseline data for eyes that had a combined procedure showed a mean IOP of 21.1 mm Hg with 2.2 medications used daily on average. At month 12, mean IOP was reduced to 16.6 mm Hg while patients were receiving just 0.1 medications daily on average.

“IOP at 12 months was below the baseline in all patients, and decreased by more than 20% in the overwhelming majority of eyes while use of medication was reduced by 95%,” Dr. Samuelson said.

Mean IOP was unchanged from the 12-month value at month 24, and mean daily medication use remained low at 0.5.

In eyes receiving the device only, mean IOP was reduced from 21.6 mm Hg at baseline to 17.9 mm Hg at month 12 and 18.6 mm Hg at month 24. Mean daily medication use decreased from 1.7 at baseline to 0.2 at month 12 and 0.5 at month 24.

“It is important to understand that the treating physicians were not encumbered from adding medications if they deemed better IOP control was needed,” Dr. Samuelson said. “The data indicate that the somewhat modest IOP reduction achieved in this population of mild to moderate glaucoma patients was felt to be acceptable to maintain control in this patient population.”

The most common adverse event in both subgroups of patients was transient hyphema (lasting <7 days), which occurred in 7 patients in the combined group (24%) and 8 patients receiving the device alone (22%). All cases but one were layered <2 mm. Peripheral anterior synechiae developed in three eyes in the combination surgery group (10.3%) and four eyes receiving the scaffold only (10.8%).

“One eye developed a retinal vein occlusion, but in my review as medical monitor I identified no significant IOP spike to which this event could be attributed to, and so it was determined to be unrelated to the procedure,” Dr. Samuelson said.

Thomas W. Samuelson, MD

E: twsamuelson@mneye.com

Data from the Hydrus I trial were presented by Thomas W. Samuelson, MD, at the 2013 meeting of the American Academy of Ophthalmology. Dr. Samuelson is an investigator and advisor to Glaukos and Ivantis.