Table 1.

Conventional glaucoma drainage devices, the trabeculectomy-modifying EX-PRESS^® device, and the new MIGS devices—summary of the current regulatory status, advantages, and disadvantages of each group of devices (aqueous shunts—valved and non-valved; MIGS devices—Schlemm’s canal, suprachoroidal, and subconjunctival devices), and effectiveness of each device in reducing IOP, as reported in selected studies.

Type of device	Site of anatomical intervention	Device (Manufacturer)	Regulatory status	Advantages	Disadvantages	% IOP reduction at follow-up (Study type)
Conventional glaucoma drainage devices	Subconjunctival space	Molteno® Glaucoma Drainage Device (Molteno Ophthalmic Limited)	CE mark, FDA approval	Larger surface area of end plate provides greater long-term IOP reduction	Delayed functioning until encapsulation of plate occurs (high IOP in the postoperative period); Greater risk of postoperative hypotony and hypotony-related complications	53.4% at 2 years (Prospective, randomised clinical trial) [26]
		Baerveldt® Glaucoma Implant (Johnson & Johnson Vision)	CE mark, FDA approval			57.4% at 5 years (Prospective, randomised clinical trial) [27]
		PAUL® Glaucoma Implant (Advanced Ophthalmic Innovations)	CE mark granted in 2017	Smaller tube diameter occupies less space in the anterior chamber angle	Complications reported so far: shallow anterior chamber, tube occlusion and exposure, hypotony requiring intervention and endophthalmitis	42.9% at 1 year (Prospective, single-arm clinical trial) [38]
		Ahmed® Glaucoma Valve (New World Medical, Inc.)	CE mark, FDA approval	Valve minimises risk of postoperative hypotony and hypotony-related complications; Allows immediate IOP reduction	Higher rate of bleb encapsulation and smaller surface area of end plate may decrease IOP-reducing efficacy; Valve malfunction can result in hypotony and hypotony-related complications	46.6% at 5 years (Prospective, randomised clinical trial) [27]
		Ahmed® ClearPath Glaucoma Drainage Device (New World Medical, Inc.)	CE mark, FDA approved since 2019	Equivalent to Baerveldt implant	Equivalent to Baerveldt implant	Equivalent to Baerveldt implant
Trabeculectomy- modifying device	Subconjunctival space	EX-PRESS® Glaucoma Filtration Device (Alcon Laboratories, Inc.)	CE mark, FDA approved since 2002	High efficacy in reducing IOP; More predictable than trabeculectomy, with less IOP fluctuations during the early postoperative period; Complications are less frequent when compared to trabeculectomy	Risk of failure as a consequence of subconjunctival fibrosis and bleb-related complications; hypotony is commonly reported, as well as erosion, displacement, and blockage of the implant	41.4% at 2 years (Prospective, randomised clinical trial) [29]
Minimally invasive glaucoma surgery (MIGS) devices	Schlemm’s canal	iStent® (Glaukos Corporation)	CE mark granted in 2004, FDA approved since 2012	Lower risk of hypotony and hypotony-related complications; Favourable safety profile	High risk of fibrosis that may lead to device obstruction; Modest IOP reduction, which makes these devices only suitable for patients with mild-to-moderate glaucoma; Not suitable for patients with high episcleral venous pressure	33.7% at 1 year (Prospective, randomised clinical trial) [30]
		iStent inject® (Glaukos Corporation)	CE mark granted in 2010			31.0% at 2 yearsa (Prospective, randomised clinical trial) [31]
		iStent inject® W (Glaukos Corporation)	FDA approval since 2020			No published studies
		Hydrus® Microstent (Ivantis, Inc.)	CE mark granted in 2011, FDA approved since 2018			37.1% at 1 year (Prospective, randomised clinical trial) [30]
	Suprachoroidal space	CyPass® Micro-Stent (Alcon Laboratories, Inc.)	Withdrawn from the global market in 2018	More effective at reducing IOP as compared with Schlemm’s canal MIGS devices	High risk of fibrosis that may lead to device obstruction; Unpredictable IOP spikes; Higher risk for (transient) hypotony	34.3% at 5 yearsa (Prospective, randomised clinical trial) [32]
		iStent SUPRA® (Glaukos Corporation)	CE mark granted in 2010, under FDA review			No published studies
		SOLX® gold shunt (SOLX, Inc.)	CE mark granted, approved in Canada			35.8 % at 5 years (Prospective, randomised clinical trial) [33]
		STARflo™ Glaucoma Implant (iSTAR Medical)	CE mark granted in 2012			38.5% at 2 years (Prospective study) [34]
		MINIject™ (iSTAR Medical)	Application for CE marking expected in 2020			39.1% at 6 months (Prospective, single-arm clinical trial) [35]
	Subconjunctival space	XEN® Gel Stent (Allergan, Inc.)	CE mark granted in 2013, FDA approval since 2016	High efficacy in reducing IOP, making these devices suitable for patients with more severe glaucoma; Possibility of applying antifibrotic agents in the subconjunctival space optimises the fibrotic response; Modulating bleb encapsulation is possible with techniques such as bleb massage or bleb needling	Risk of failure as a consequence of subconjunctival fibrosis and bleb-related complications	36.3% at 1 year (Prospective, single-arm clinical trial) [36]
		PRESERFLO™ MicroShunt (Santen)	CE mark granted in 2012, under FDA review			46.7% at 5 years (Prospective, nonrandomized, single-arm clinical trial) [101]

^aIn combination with cataract surgery.