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Komzak et al. Mini-invasive Surg 2021;5:13 I http://dx.doi.org/10.20517/2574-1225.2020.103 Page 5 of 14

A

B

Figure 1. First generation iStent trabecular microbypass stent (A). Second generation iStent inject trabecular microbypass stent (B). This
[5]
figure is quoted with permission from Hooshmand et al. .
MIGS procedures that have a reasonable evidence base. MIGS approaches that were identified include:
iStent, iStent inject, Hydrus, Ab-interno Canaloplasty, Trabectome, CyPass, iStent Supra, Xen, Preserflo
microshunt, Endocyclophotocoagulation, SLT and the emerging MIGS including MINIject, Beacon
Aqueous Microshunt and the extended-release drug delivery systems.

THE DIFFERENT TYPES OF MIGS APPROACHES
Including mechanism of action, effectiveness, and safety profile.

MIGS aimed at improving outflow through Schlemm’s canal
iStent and iStent inject: Mechanism of action
The iStent and iStent inject (Glaukos Inc, Laguna Hills, CA, USA) are first and second generation
trabecular microbypass stents, aimed at improving outflow of aqueous humor through the trabecular
[5]
meshwork into Schlemm’s canal (both pictured in Figure 1) . Both are made of heparin coated titanium,
and while the iStent is 1 mm × 0.3 mm in size, the iStent inject is significantly smaller at only 360 µm ×
230 µm in size. Both are inserted using a disposable implantation device through a clear corneal incision
as a single procedure or in combination with cataract extraction, and in the case of iStent inject 2 devices
are loaded into the injector and can be placed at 30˚-60˚ apart. Both devices are usually followed up with
a 4-week course of topical anti-inflammatory and anti-infective medication to reduce the risk of surgical
[26]
complications . Generally, iStent or iStent inject is indicated in mild to moderate glaucoma with the aim
to reduce dependence on topical medications and/or to reduce IOP. These trabecular microbypass devices
have an advantage in that they are very small devices, and so are unlikely to cause endothelial damage in
patients with shallow anterior chambers.