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Ab interno approach to the sub-conjunctival space: materials and biocompatibility of a minimally invasive collagen glaucoma implant

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Session Details

Session Title: Glaucoma I

Session Date/Time: Sunday 14/09/2014 | 08:00-09:30

Paper Time: 08:00

Venue: Auditorium

First Author: : I.Kersten-Gomez GERMANY

Co Author(s): :    M. Elling   B. Dick           

Abstract Details

Purpose:

To describe the development of a novel, soft and permanent, minimally invasive ab interno collagen implant to optimize aqueous drainage to the subconjunctival space.

Setting:

Paper includes animal and benchtop studies performed at various laboratories, as well as human trial data from 13 surgical centers, in both hospitals and private settings – conducted by 19 surgeons and prospective clinical pilot-study at University Eye Hospital of Bochum, Germany with 1 surgeon.

Methods:

Safe placement ab interno through sclera requires a flexible yet firm material that maintains shape without disrupting tissue planes. A cross linked collagen gelatin that is hard when dry but soft when hydrated was tested. Using a bending angle value as a reference, several tests were performed to compare bending forces between the gelatin stent and the most common material used to drain aqueous humor (silicone). Preclinical and clinical testing was also used to determine the optimal lumen size, length, diameter, tube rigidity, durability, flexibility and of the stent. At the University Eye Hospital of Bochum these micro-stents were tested clinically in a prospective randomized trial from February 2010 to 2012 with follow-ups over 3 years in 23 patients.

Results:

Hydrolytic stability showed no evidence of hydrolytic degradation. A 10 year accelerated flow testing showed no changes in implant lumen or wall thickness. Data out to 6 years confirm that the implant remains stable and patent. Preclinical and human eye testing shows the implant does not seem to occlude inside the lumen and the implant material does not appear to cause any tissue reaction. The implant gives a flow of 0.02µl/sec or 1.2µl/min, (at 5 mmHg pressure gradient), thus providing around 6-8 mmHg flow resistance, which essentially eliminates hypotony. The high implant flexibility and small diameter avoid implant-tissue irritation and extrusion. In the clinical trial at the University Eye Hospital of Bochum the intraocular pressure decreased from a mean of 21 mmHg (+/- 2.3) to 15.4 mmHg ( +/- 2.9) for a mean reduction of about 27 % from baseline at month 12. The number of patients who achieved success (IOP between 5 to 18 mmHg and 20 % reduction) was 88.9 %.

Conclusions:

Subconjunctival drainage of aqueous fluid has been a cornerstone of glaucoma surgery for over a century. The ab interno placement of the gel stent offers a unique alternative for lowering intraocular pressure with a minimally invasive procedure, minimal conjunctival tissue disruption, restricted flow to avoid hypotony, and long term safety. The clinical prospective study could confirm the implants to be safe and effective with no major adverse events (merely few minor complications) in patients with solo or combined cataract-glaucoma procedure.

Financial Interest:

One or more of the authors... research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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