Aqueous drainage tube provides trabeculectomy-like efficacy

Take-home message: In a study including 23 eyes with a transscleral micro-lumen aqueous drainage tube after failing maximum tolerated medication, reductions in the mean IOP were observed as well as in the mean number of medications per day.

By Cheryl Guttman Krader; Reviewed by Juan F. Batlle, MD

Santo Domingo, Dominican Republic-Implantation of a transscleral micro-lumen aqueous drainage tube (InnFocus MicroShunt, InnFocus) by itself, or in combination with phacoemulsification, is safe and provides significant and durable IOP-lowering, said Juan F. Batlle, MD.

In most patients, IOP is lowered into the range of 10 to 13 mm Hg and remains stable at that level with follow-up to 3 years, said Dr. Batlle, director, Centro Laser, and director, Elias Santana Charity Hospital, Santo Domingo, Dominican Republic.

“This level of IOP falls within the zone identified in the Advanced Glaucoma Intervention Study as being optimal for preventing vision loss, and matches what can be achieved with trabeculectomy,” he said.

However, the microshunt has a more favorable safety profile than filtering surgery, as so far it is avoiding hypotony-related and late bleb complications that can necessitate surgical intervention, Dr. Batlle noted.

The transscleral micro-lumen aqueous drainage tube received the CE Mark in January 2012, but is still investigational in the United States.

About the study

Dr. Batlle has published his experience with the microshunt [J Glaucoma. 2016;25(2):e58-65] in a study enrolling 23 eyes that would be considered candidates for trabeculectomy or a tube procedure. All had glaucoma inadequately controlled on maximum tolerated glaucoma medication and an IOP between 18 and 40 mm Hg.

In 14 eyes, the transscleral aqueous drainage tube was implanted as a standalone procedure, while the remaining 9 eyes also underwent phacoemulsification with IOL implantation.

In all cases, mitomycin-C (MMC) 0.4 mg/mL was applied intraoperatively for 3 minutes.

All eyes were evaluable for follow-up at 1 year, and 22 eyes were seen at the 2-year and 3-year visits.

Mean IOP at baseline was 23.8 ± 5.3 mm Hg at baseline and measured 10.7 ± 2.8 mm Hg at 1 year, 11.9 ±3.7 mm Hg at 2 years, and 10.7 ±3.5 mm Hg at 3 years, with the latter value representing a 55% reduction from baseline.

Results were similar in subgroup analyses of eyes undergoing microshunt implantation alone or as a combined procedure.

The IOP-lowering benefit was accompanied by a significant reduction in need for IOP-lowering medication. Mean number of medications used per patient was 2.4 preoperatively and was only 0.3 at 1 year, 0.4 at 2 years, and 0.7 at 3 years. At last follow-up, two-thirds of the patients were on no medications, Dr. Batlle noted.

Measure of success

He also analyzed success rates and reported that it was 95% at 3 years using a definition based on a stringent IOP cutoff of ≤14 mm Hg plus additional criteria requiring at least a 20% decrease from baseline, no additional glaucoma surgery requiring an operating room setting, no loss of light perception vision, and no chronic hypotony, or use of glaucoma medication.

The only failure occurred in one patient at 27 months who developed an encapsulated bleb. In that individual, a second microshunt was inserted without explantation of the first device and resulted in lowering of IOP into the low teens.

“The only other postoperative intervention performed in this series of 23 eyes was a single case of a bleb needling procedure,” Dr. Batlle said.

The most common complications encountered in the study, hypotony (13%) and choroidal effusion (8.7%), occurred early after surgery, were transient, and resolved without any intervention. No serious adverse events occurred during longer follow-up, and there have been no cases of bleb infection or leaks nor any issues with device migration or erosion.

“The device is constructed of poly(styrene-block-isobutylene-block-styrene (“SIBS”), which is an inert and highly biocompatible material that is soft and conforms to the curvature of the eye. We believe that the material features combined with placement of the device beyond the eyelid excursion accounts for the lack of device exposure in the absence of using a scleral patch,” Dr. Batlle said.

Implantation of the microshunt is performed in an ab externo procedure that Dr. Batlle describes as relatively simple because it avoids the need for scleral dissection sclerostomy, iridotomy, and tensioning sutures. It is also relatively quick, taking less than 12 minutes to complete once surgeons complete the learning curve.

The device is inserted through a 3-mm scleral tract formed under the limbus with a 25-gauge needle. Dr. Batlle was originally creating the tract with a 27-gauge needle, but shifted to using the larger needle that has made insertion of the device insertion easier and faster without causing periannular leakage.

Juan F. Batlle, MD

E: jbatlle55@gmail.com

Dr. Batlle is a paid consultant to InnFocus. The study is supported by a grant from InnFocus.

Santen to Acquire InnFocus

Osaka, Japan, and Miami-Santen Pharmaceutical Co. Ltd. and InnFocus Inc. have entered into a definitive agreement under which Santen will acquire privately held InnFocus, developer of the glaucoma implant device (InnFocus MicroShunt).

“With this acquisition, Santen will strengthen our glaucoma pipeline and stay at the forefront of innovation in ophthalmology,” said Akira Kurokawa, president and chief executive officer of Santen. “I am truly excited about the [device] as a new and effective treatment option that should significantly improve patient outcomes.”

“In addition to reducing IOP, the [device] does not require simultaneous cataract removal, unlike many micro-invasive glaucoma surgery technologies,” said Randy Lindholm, executive chairman of the Board of InnFocus. “The InnFocus team is very pleased to be joining Santen and its global effort to address this growing and important segment of the ophthalmic market.”

Under the terms of the agreement, Santen will acquire InnFocus for an upfront payment of USD $225 million, plus performance-based consideration upon achievement of certain development, regulatory and commercial milestones.