Anterior Segment-Optical Coherence Tomography Bleb Morphology Comparison in Minimally Invasive Glaucoma Surgery: XEN Gel Stent vs. PreserFlo MicroShunt

Abstract

Background: The purpose of this study is to compare the morphology of six-month follow-up blebs created by a subconjunctival glaucoma surgical device (XEN45) to those created by a PreserFlo MicroShunt with a sub-Tenon insertion, utilizing AS-OCT. Methods: A retrospective study of 29 eyes who underwent XEN45 implantation and 29 eyes who underwent PreserFlo MicroShunt implantation. The patients were analyzed at 24 h, 1 week, 1 month, 3 months and 6 months. At each visit, the maturation and morphological alterations of the blebs were observed, as well as connections with the IOP. Results: In both groups, IOP showed significant reduction at all follow ups (p < 0.0001). In XEN group, the most common bleb morphology in the immediate postoperative was the subconjuntival separation type (42%) followed by the uniform type (34%), with a trend inversion at 6 month follow up (51% of uniform type). On the contrary, the most common morphology after PreserFlo was the multiple internal layer (55%), which showed a tendency to reduce over time and was substituted by the microcystic multiform, whose percentage increased over time (17% at day 1 vs. 44% at month 6). Uniform appearance was associated by the posterior episcleral fluid (PEF) lake presence. Both horizontal and vertical diameters significantly increased over time. Conclusion: XEN and PreserFlo implantation resulted in the production of diffuse blebs with different characteristics, which may influence IOP lowering capacity and bleb revisions necessity over time.

Single versus Double PreserFlo MicroShunt Implantation in Glaucoma Patients: A Retrospective Cohort Study

“…However, as the external end of the PreserFlo MicroShunt is placed under the Tenon’s capsule, this type of MIGS drainage type has been shown to cause a large and distinct fluid accumulation between the sclera and Tenon’s capsule in addition to the pre-known appearance of intra-/subconjunctival fluid distributions. Gambini et al [12] who first described this phenomenon, termed it posterior episcleral fluid lake. Since this episcleral fluid lake appears like a homogenously fluid-filled balloon, we believe it is easier with this type of bleb to keep the tissue layers apart from each other and hence prevent tissue fibrosis compared to diffuse intra-/subconjunctival blebs commonly seen after trabeculectomy, provided that it is constantly supplied by aqueous humor.…”

Comparison of Bleb Morphology following PRESERFLO® MicroShunt and Trabeculectomy Using Anterior Segment OCT

“…Patients with functional blebs attending follow-up visits from the 5th week postsurgery onwards were assessed using anterior segment optical coherence tomography (AS-OCT). Blebs within the initial 4 weeks post-surgery were omitted due to their rapid morphological changes during this early phase [13,18]. A functional bleb was characterized by an intraocular pressure (IOP) of ≤18 mmHg and a reduction of ≥20% from the pre-operative IOP (at the time of surgical indication), without the use of medications.…”

“…It is crucial to acknowledge these variations to prevent misinterpretation of bleb morphology. Recent studies on drainage shunts indicate that blebs resulting from an ab-interno approach (such as those following XEN-Gel-Stent, AbbVie Inc., Chicago, IL, USA) appear to have smaller dimensions (width, height, and length) compared to those formed through an ab-externo approach (such as PRESERFLO) [13,14].…”

Evaluation of ocular surface following PreserFlo Microshunt implantation: Functional outcomes and quality of life

“…18 This technique allows to create diffuse and posterior blebs with a repeatable morphology, similar to those described for functioning TB blebs. 19,20 As of now, there are no reports in literature regarding the effects of this minimally invasive technique on ocular surface, including both post-operative adverse effects and QOL changes, as a consequence of drugs burden reduction. Starting from this assumption, the aim of this research is to evaluate the impact of PreserFlo Micro-Shunt implantation on the ocular surface, focusing on both objective parameters and subjective indexes.…”

“…It is inserted via a 3‐mm long scleral tract created with a 25G needle and implanted ab externo, with the goal of maintaining a continuous aqueous outflow through the tube's lumen to a posterior position at least 7‐mm away from the limbus, behind Tenon's capsule 18 . This technique allows to create diffuse and posterior blebs with a repeatable morphology, similar to those described for functioning TB blebs 19,20 …”