Taking the guesswork out of MIGS with ABiC.
Whereas other MIGS procedures treat only one aspect of aqueous outflow, ABiC™ comprehensively accesses, catheterizes, and viscodilates the trabecular meshwork, Schlemm’s canal, and importantly, the distal outflow system, beginning with the collector channels. Only ABiC™ comprehensively addresses all aspects of potential outflow resistance – thus removing the guesswork inherent in other MIGS procedures.
During the ab-interno MIGS procedure, ABiC™ utilizes a process of viscodilation of Schlemm’s canal to flush out the natural outflow channels, without damaging tissue and without leaving behind a stent or shunt – achieving an average reduction in mean IOP of 30%, combined with a 50% reduction in medication burden.*
Glaucoma: Site(s) of Resistance?
One of the challenges associated with glaucoma and its treatment is that the location of increased aqueous outflow resistance – and how this resistance is generated – is unclear. If a glaucoma surgeon were to remove the site(s) where increased outflow resistance resides, IOP would fall. However, if it is not possible to identify the site(s) of increased outflow resistance in a specific POAG eye, it is difficult to determine which parts of the outflow system are more relevant than others in terms of lowering IOP. Consequently, it is important to address all aspects of the ocular outflow system.
ABiC and the Collector Channels
ABiC is the only currently available MIGS procedure to address blockages in the collector channels.
In a healthy eye, aqueous humor drains from the anterior chamber through progressively smaller channels of the trabecular meshwork into the circumferentially oriented Schlemm’s canal. From Schlemm’s canal, circuitous channels, known as the collector channels, wind their way toward the surface of the sclera through the intrascleral venous plexus system, joining the episcleral vasculature, which drains into the venous system. It is important to note that the collector channels are not evenly distributed around Schlemm’s canal circumferentially and that outflow is segmental, higher in areas close to the large collector channels.
Studies undertaken in human POAG eyes by Haiyan Gong, MD, PhD (University of Boston) have shown that many of the collector channels may be blocked with herniated trabecular meshwork tissue at 0mmHg and become progressively worse as IOP rises1. This herniated tissue does not recede in POAG eyes although it does in normal eyes. Cannulating the whole of Schlemm’s canal with Canaloplasty, via a process of 360-degree visco-dilation, may “pop” open these herniations and enable full access to collector channel ostia for the egressing aqueous. In the case of other glaucoma treatments, where only a segment of Schlemm’s canal is addressed, or where the trabecular meshwork is targeted in isolation, any herniated tissue would most likely prevent improved outflow.
Research Summary: Haiyan Gong
In POAG eyes fixed at 0 mmHg (N=5), 73 collector channel ostia regions were examined, with 51 showing herniations (70%). In POAG eyes fixed at 10 mmHg (N=2), 22 collector channel ostia regions were examined, with 21 showing herniations (95%). In contrast, in normal eyes fixed at 0 mmHg, 53 collector channel ostia regions were examined, with 8 herniations found (15%). Whilst these herniations were found to be reversible in normal eyes, they were irreversible in the POAG eyes.
MIGS Mechanism of Action
|Physiological Outflow Pathway||Non-Physiological Pathway|
|Collector Channels||Trabecular Meshwork||Schlemm’s Canal||Subconjunctival Space||Supraciliary space|
|XEN Gel Stent||YES|
ABiC™ works by restoring the natural outflow pathways for aqueous humor, using a technique similar to angioplasty. During the procedure, ABiC™ comprehensively opens up all components of the eye’s natural outflow system – 1. Trabecular meshwork, 2. Schlemm’s canal, and 3. The Collector Channels and distal outflow system.
iStent acts as a as a trabecular micro-byass by allowing aqueous humor to flow directly from the anterior chamber into Schlemm’s canal, thus circumventing the trabecular meshwork.
6.3mm stent facilitates outflow from the anterior chamber to the suprachoroidal space. It acts to lower IOP by bypassing the physiological flow routes.
XEN GEL Stent
6mm stent placed in the subconjuctival space to create a filtering bleb. It acts to lower IOP by bypassing the physiological flow routes.
*228-eye ABiC 12-Month Case Series Data, presented at ASCRS 2016. Data on file. Ellex Medical.