Table 1. Advantages and disadvantages of commercially available GDIs for anterior chamber use.

Shunt type	Commercially-available GDI	Plate material	Surface area	Advantages	Disadvantages
Non-valved	Baerveldt	Silicone	250 mm2	Larger surface area of plate(s) to act as reservoir that may provide increased IOP lowering effect	Delayed functioning until encapsulation of plate occurs More intensive post-operative follow-up required Greater risk of diplopia Greater risk of hypotony
			350 mm2
	Molteno	Polypropylene	Single plate 130 mm2
			Double plate 270 mm2
	Ahmed Clear Path	Silicone	250mm2
			350mm2
Valved	Ahmed	Polypropylene	96 mm2 (S3)	Immediate post-operative IOP lowering effect Plate placed in between recti muscles hence lower risk of diplopia Valve minimises risk of post-operative hypotony	Higher rate of bleb encapsulation Smaller surface area of plate to act as a reservoir that may provide decreased IOP lowering effect Defective valve mechanism can result in hypotony or obstructed outflow
			184 mm2 (S2)
			364 mm2 (B1)
		Silicone	96 mm2 (FP8)
			184 mm2 (FP7)
			364 mm2 (FX1)

GDI: Glaucoma drainage implant. Adapted and updated from Schwartz et al 2006^[5] and Gedde et al 2011^[6].