Deep Sclerectomy vs Xen in Solo Procedure

Glaucoma is the leading cause of irreversible blindness in the world and the second leading cause of blindness after cataract after the age of 50. Lowering intraocular pressure (IOP) is the only treatment option to prevent visual field degradation. While medical treatment and selective laser trabeculoplasty are considered first-line options in open-angle glaucoma, the surgical option is considered in patients who have uncontrolled IOP under maximal tolerated medical treatment. In this situation, trabeculectomy or deep nonperforating sclerectomy may be performed. Although it is uncertain whether SPNP is superior to trabeculectomy, which is considered the gold standard of surgery, SPNP is a procedure that offers a better quality of life and fewer intra- and postoperative complications. SPNP was first described by Zimmerman. It consists in peeling off the internal wall of Schlemm's canal and the juxta-canalicular trabeculum which represent the main resistances to the evacuation of the aqueous humor. The trabecular meshwork is left intact and acts as a filter membrane between the subconjunctival space and the anterior chamber. The addition of mitomycin (MMC) is necessary because it is associated with better IOP control and greater surgical success. Although postoperative procedures such as needling or Nd:YAG laser-assisted gonioponctures are often required, SPNP offers good long-term results in patients who are naïve to any filtering surgery.

Minimally invasive surgery has been used more and more over the last 10 years. It aims to reduce surgical complications in comparison to classical filtering procedures while respecting the eye's own anatomy. Several devices have been invented to increase aqueous humor elimination. They can be implanted ab-interno or ab-externo and can be implanted in the suprachoroidal space, in Schlemm's canal or in the subconjunctival space. The XEN gelstent (Allergan, Dublin, Ireland) is placed ab-interno between the subconjunctival space and the anterior chamber, either in combination with cataract surgery or as a solo procedure.

The aim of the study is to compare the surgical success of these 2 techniques. No study has ever compared these 2 surgeries in solo procedure. A recent retrospective trial compared them in combined procedures without showing significant differences in IOP reduction. Nevertheless, the short follow-up period of 9 months may have been insufficient to show a real difference.