Ab Internal Stent

Abstract

These devices also belong to the group of MIGS techniques. As mentioned in previous chapters, the MIGS procedures reduce the intraocular pressure (IOP) and improves the outflow of aqueous humor (and to a lesser degree, reduces the production of aqueous by the ciliary bodies). The devices that increase the aqueous humor outflow can influence various physiological pathways: some procedures improve the drainage of the aqueous humor into the Schlemm Canal by removing the resistance by the trabeculate (the conventional drainage pathway) or by by-passing it. Other procedures improve uveo-scleral drainage (non-conventional drainage pathway) creating a connection between anterior chamber (AC) and the supra-choroidal space. The micro-incisional approach of MIGS is for the most part ab interno; this would appear to be less invasive and avoids incisions and the scars of the conjunctiva and sclera, preserving the natural drainage pathways for the aqueous humor (even though some authors believe that the ab externo approach can be equally successful). One new ab interno device with a sub-conjunctival approach is the Xen Glaucoma Implant.