Aqueous shunt implantation in glaucoma

Abstract

Aqueous shunts or glaucoma drainage devices are increasingly utilized in the management of refractory glaucoma. The general design of the most commonly-used shunts is based on the principles of the Molteno implant: ie. a permanent sclerostomy (tube), a predetermined bleb area (plate) and diversion of aqueous humour to the equatorial region and away from the limbal subconjunctival space. These three factors make aqueous shunts more resistant to scarring as compared to trabeculectomy. The two most commonly used shunts are the Ahmed Glaucoma Valve, which contains a flow-restrictor, and the non-valved Baervedlt Glaucoma Implant. While the valved implants have a lower tendency to hypotony and related complications, the non-valved implants with larger, more-biocompatible end plate design, achieve lower intraocular pressures with less encapsulation. Non-valved implants require additional suturing techniques to prevent early hypotony and a number of these methods will be described. Although serious shunt-related infection is rare, corneal decompensation and diplopia are small but significant risks.

<p>Monitoring and management of the patient with pseudoexfoliation syndrome: current perspectives</p>

“…Implantation of these devices appears to have similar efficacy to trabeculectomy in lowering IOP, but requires less intensive postoperative follow-up. The predictability of aqueous shunt surgery is still moderate at best, though probably greater than that after trabeculectomy 96,97…”

“…Glaucoma-drainage devices or aqueous shunts are artificial filtering devices that lower IOP by draining aqueous humor to the external subconjunctival space. Glaucoma-drainage devices are indispensable tools for the management of glaucoma, especially in eyes with previously failed trabeculectomy and complicated glaucoma, such as uveitic glaucoma, neovascular glaucoma, and pediatric glaucoma 96,97. Implantation of these devices appears to have similar efficacy to trabeculectomy in lowering IOP, but requires less intensive postoperative follow-up.…”

Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits

“…Reducing the IOP is the main therapeutic goal [5], which can be achieved with surgical interventions [6]. Glaucoma drainage devices (GDDs) are of growing importance in comparison to laser surgery and trabeculectomies [7, 8]. Despite many different implant models, the approach is always to increase aqueous humour drainage, leading to a reduction in IOP [9].…”

“…Despite many different implant models, the approach is always to increase aqueous humour drainage, leading to a reduction in IOP [9]. The Molteno implant from 1969 is the precursor of the majority of GDDs [3, 8]; a tube implanted into the anterior eye chamber is connected to a plate fixed at the sclera and covered by conjunctiva. Around that plate, aqueous humour drained from the anterior eye chamber forms a filtering bleb.…”

“…The success rates of different common implant models varied between 72% and 79% within the time period of 1969–2003, thus underlining the need for an improved GDD [9]. Intraoperative complications, usually based on tissue injuries, are rare [8]. Hyphaema is the most common intraoperative complication in glaucoma surgery [11, 12].…”