Ab Interno Gelatin Stent With Mitomycin C Using Targeted Supra-tenon's Placement
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Observational

Summary: 
      The Xen-45 gelatin microstent is a novel, bleb-forming microinvasive glaucoma surgery (MIGS).
      Despite demonstrating similar efficacy and safety to trabeculectomy (traditional surgery),
      the Xen-45 gelatin microstent continues to suffer from occasional surgical failure due to
      fibrosis of the filtering bleb, and obstruction of the stent. During surgery, placement in a
      surgery known as supra-tenon's space is believed to maximize aqueous outflow, while
      preventing obstruction, limiting fibrosis of the bleb, and promoting long-term patency.
      Despite the theoretical merits, long-term data of outcomes after targeted supra-tenon's
      placement is needed to fully assess its potential in improving Xen-45 microstent outcomes.
    

Detailed description: 
      The Xen-45 gelatin microstent (Allergan, Dublin, Ireland) is a novel, bleb-forming
      microinvasive glaucoma surgery (MIGS). Creation of a filtering bleb through the gel stent and
      under the conjunctiva lowers intraocular pressure (IOP) by bypassing the natural outflow
      pathway of aqueous. A recent retrospective cohort study showed comparable safety and risk of
      failure to trabeculectomy. Amongst the main advantages of this device is the ability to
      create a bleb without dissecting and disrupting tissue, thus decreasing the amount of wound
      healing and potentially limiting bleb failure. However, despite demonstrating similar
      efficacy and safety to trabeculectomy,2 the Xen-45 gelatin microstent continues to suffer
      from occasional surgical failure due to fibrosis of the filtering bleb, and obstruction of
      the stent. Although antimetabolites, such as mitomycin C, have decreased reactionary wound
      healing that can result following surgery, fibrosis may still occur, especially when the
      components of the Xen-45 gelatin microstent are in close proximity to the fibroblastic
      structures of tenon's fascia.Tenon's capsule resembles a sponge-like layer with multiple
      adhesions to the overlying conjunctiva and underlying episclera. Implantation of the XEN
      within this space creates a higher risk of obstruction and subsequent failure. To ensure the
      lowest potential for occlusion, bleb scarring, and failure, one must ensure careful placement
      of the device in the subconjunctival space, avoiding intra-tenon's placement. Placement in
      the supra-tenon's space is believed to maximize aqueous outflow, while preventing
      obstruction, limiting fibrosis of the bleb, and promoting long-term patency. Despite the
      theoretical merits, long-term data of outcomes after targeted supra-tenon's placement is
      needed to fully assess its potential in improving Xen-45 microstent outcomes.
    

Intervention name(s): XEN-45 gelatin microstent
Intervention type(s): Device
Intervention description(s): Placement either in the subconjunctival space or supratenon's area
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Patients aged 30-90 with primary or pigmentary/pseudoexfolliative open angle, primary
        closed angle, or combined mechanism glaucoma with IOP of 18-40 mmHg on maximum tolerated
        medical therapy who received a gelatin stent with MMC at Prism Eye Institute from June 2012
        to August 2019.