Table 1.

Comparison of Xen implantation techniques

	Ab interno open conjunctiva	Ab externo open conjunctiva
Technique	1. Corneal traction suture is optional 2. Conjunctival peritomy and dissection are performed 3. Main and side port incisions (clear cornea) are made—AC is filled with cohesive OVD 4. The injector is inserted through he main incision, across anterior chamber towards the target area. 5. The needle enters the trabecular meshwork and is advanced through the sclera exiting 2 mm posterior to limbus using countertraction. 6. The stent is deployed and adjusted as needed. 7. Flow is confirmed after removing OVD and priming the bleb 8. Tenon’s layer and conjunctiva are sutured closed	1. Corneal traction suture may be placed in the superior cornea 2. Conjunctival peritomy and dissection are performed 3. Side port is optional—only needed if using OVD 4. The injector is placed in sclera 2–2.5 mm from the limbus; using the traction suture for countertraction 5. The needle is advanced through sclera until visible in AC 6. The stent is deployed and adjusted as needed 7. Flow of aqueous is confirmed by visualizing beading at the distal end of the stent 8. Tenon’s layer and conjunctiva are sutured closed
Advantages	1. Better control of placement of stent in the angle 2. Can be easily combined with phacoemulsification	1. Expands the targeted area of implantation to the supero-temporal quadrant 2. Can be performed without corneal incisions or viscoelastic use 3. Easiest transition for glaucoma surgeons 4. Safer in phakic eyes
Disadvantages	1. Requires maneuvers in the AC 2. Can be challenging in eyes with corneal opacification	1. Entry into AC cannot be performed under gonioscopic guidance