Innovations in aqueous filtration

New device may control IOP by shunting aqueous directly to the ocular surface.

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Current glaucoma devices and procedures shunt aqueous to one of three places – the subconjunctival space, conventional outflow channels or the suprachoroidal space. Yet each has its drawbacks in terms of limited IOP reduction or complication risks. A fourth option, a device shunting aqueous directly to the conjunctival surface, may be on the horizon, Patrick Riedel MD told the innovators session at the ASCRS ASOA 2019 Annual Meeting in San Diego, USA. Early patient studies suggest the Beacon Aqueous Microshunt may provide consistent, long-lasting IOP reduction on par with filtration surgery with a much lower complication profile – with improved tear volume as a bonus. Preventing infection Conceived 20 years ago by Minneapolis, USA, MIGS pioneer J David Brown MD, MicroOptx was formed in 2014 to develop the device. It is implanted through the conjunctiva, slightly posterior to the limbus through a paracentesis-type incision, with one end in the anterior chamber over the iris and the other on the ocular surface. The arrowhead-shaped device is 3.1mm long and 0.19mm thick with a 1.7mm wide external flange. Aqueous exits the anterior chamber through a central channel measuring 30x48 microns. The shell is composed of two layers of thermoplastic polyurethane to resist impact, while the channel is embedded into a layer of polyethylene glycol (PEG) to resist biofouling. Beacon went through extensive development to mitigate the obvious risk of retrograde pathogens causing endophthalmitis, Dr Riedel said. Laminar flow from the anterior chamber to the ocular surface is fast enough to prevent backwash and pathogen attachment, while hydrophilic PEG also prevents adherence of bacteria and protein. “Pathogens simply cannot gain a foothold,” said Dr Riedel, also of Minneapolis. IOP Lowering In porcine studies of 105 animals followed up to six months, the Beacon produced significant and persistent IOP lowering with no infections – even in eight animals that were challenged with bacteria on the surface for 10 days. “When we tried to infect these eyes we were unable to get endophthalmitis,” Dr Riedel said. More importantly, implants in 15 patients in the USA and Europe showed a mean IOP reduction from 27mmHg to 13mmHg, and greater than 20% reduction in 13 from baseline to the last visit, mostly at six months post-surgery. Similarly, 14 of 15 patients required no meds to control IOP, with a mean reduction from 2.5 to 0.08 per patient. Two patients reported mild discomfort, while six devices experienced blockages with one explanted for persistent blockage due to pseudoexfoliation. All patients were at least somewhat satisfied. A study involving 90 patients at 15 sites is planned. Roy Martin: rmartin@microoptx.com
Tags: iop glaucoma