10.3 Implants |
77 |
|
|
of the OVD will cause some parts of the trabecular meshwork to rupture. The scleral ßap is closed very tightly so that no Þltering bleb will develop.
10.3Implants
10.3.1Canaloplasty
The preparation is the same as that for viscocanalostomy, but the entire SchlemmÕs canal is cannulated with a small, ßexible Þber optic microcatheter. A non-resorbable suture is connected to the Þber, the Þber is pulled back and the suture is knotted under tension. The septae of SchlemmÕs canal are disrupted and the canal is opened because of the tension of the suture. In gonioscopy the blue suture might be detected in the posterior trabecular meshwork.
10.3.2iStent Trabecular Micro-Bypass
Fig. 10.6 iStent positioned exactly in the chamber angle at the functional trabecular meshwork (Courtesy S. Windsor, Glaucos)
A small, L-shaped stent (1×0.5×0.25 mm, snorkel opening 120 mm) made of titanium is implanted ab interno in the trabecular meshwork and SchlemmÕs canal (Fig. 10.6). It is easily detectable by gonioscopy.
10.3.3Ex-PRESS Mini Glaucoma Shunt
A 3-mm long tube with an external diameter of 400 mm (27 gauge) and a lumen of 50 mm is implanted at the site where the tissue would be excised in trabeculectomy. A spur on the surface of the tube avoids extrusion and a plate intrusion. An iridectomy is not necessary.
10.3.4SOLX Gold Shunt
A 24-carat gold plate (3.2 mm wide posteriorly and 2.4 mm wide anteriorly, 5.2 mm long) with many tiny perforations and microchannels is implanted in the supraciliary/suprachoroidal space to enhance the outßow. Newer devices
Fig. 10.7 Two small plastic tubes reach into the anterior chamber
(GMS Plus) with increased thickness and more pores are offered.
10.3.5Tube Shunts
The principle of all these devices is to create a bypass for outßow. A plastic tube is introduced into the chamber angle (or in the pars plana in vitrectomized eyes) and is connected to a plastic or silicone plate, which is Þxed externally on the sclera behind the equator of the globe. The plates have different sizes. Some have a valve (Baerveldt), and some do not (Ahmed, Molteno). In gonioscopy the plastic tube penetrates the chamber angle structures and reaches up to 2Ð3 mm onto the surface of the iris (Fig. 10.7).