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Glaucoma filtration surgery (GFS) has been shown to be more effective at preventing disease progression than other primary treatment modalities in open angle glaucoma.1 2 If it were possible to avoid complications associated with poor flow control, primary GFS would probably be offered more widely.
Trabeculectomy, the procedure of choice in conventional GFS, has remained essentially unchanged for over a quarter of a century. Local control over wound healing with antimetabolite agents such as 5-fluorouracil and mitomycin C has improved the prognosis for cases with high risk of filtration failure; but flow control remains inexact despite the introduction of a variety of suture adjustment techniques.
Glaucoma drainage devices (GDDs) have the potential to regulate flow consistently, eliminating hypotony after GFS. Design, material, and manufacturing deficiencies have left this potential unfulfilled in existing GDDs, all of which exhibit problems with poor flow control and suboptimal tissue compatibility. The role of GDDs in contemporary GFS remains poorly defined, but possibilities offered by new biomaterials and the goal of accurate flow control have stimulated considerable recent interest in GDD development. This review traces the progress of GDD design through to the present and beyond.
Early glaucoma drainage devices
In 1906, horse hair3 was placed through a corneal paracentesis in an attempt to drain a hypopyon externally. The same technique was later used to treat two patients with painful absolute glaucoma.4 Sporadic attempts using implants to shunt aqueous to a variety of unconventional sites, including the vortex veins5 and the nasolacrimal duct,6 have since been reported. Results were generally unfavourable or too poorly documented to evaluate, and attention has focused on devices shunting aqueous fluid to the subconjunctival space as with conventional GFS.
The first translimbal GDD, reported by Zorab7 in 1912, was silk thread used as a seton to aid drainage …