Effect of the outer stent position on efficacy after minimally invasive transscleral glaucoma gel stent implantation

Abstract

Purpose: The outer stent lumen can be located either deeper (in or under Tenon's layer) or more superficially in the conjunctival stroma after the transscleral XEN Glaucoma Gel Microstent (XEN-GGM; Allergan Plc., USA) implantation. The present study aimed to investigate the effect of the postoperative conjunctival implant position on surgical success and intraocular pressure (IOP) after XEN-GGM. Methods: Prospective data from 66 consecutive open-angle glaucoma eyes of 54 patients were collected preoperatively and 1 and 2 weeks, and 1, 6 and 12 months postoperatively. The layer of implantation was determined in the first month postoperatively as intra-and subtenon or intraconjunctival depending on the location of the outer lumen of the stent in OCT (Visante OCT; Zeiss, Germany). Primary outcome measures were differences in relative IOP reduction at 12 months between the two groups. Further, complete and qualified surgical success, number of secondary needlings and number of IOP-lowering medications and absolute IOP were assessed. Results: Relative IOP reduction was higher in intra-and subtenon group (n = 37/ 66, 56%) at week 1 (À54% versus À19%, p < 0.001), week 2 (À39% versus À21%, p = 0.02), month 1 (À42% versus À28%, p = 0.035) and month 12 (À39% versus À24%, p = 0.024). The mean absolute IOP was lower in intra-and subtenon group at week 1 (10.8 [95%CI,.0] mmHg, p < 0.001) and months 12 (13.9 [95%CI,] mmHg, p = 0.041). At month 6, a lower burden for IOP-lowering medication was shown for the intra-and subtenon group (0.2 AE 0.5 versus 1.0 AE 1.1, p = 0.034). The mean number of secondary needlings, which were done in 47/66 (71%) of the eyes, was lower in the intra-and subtenon group in the first year (1.9 AE 1.7 versus 1.2 AE 1.2, p = 0.03). Qualified surgical success was higher in the intra-and subtenon group (90% versus 61%, p = 0.01) after 1 year. Conclusion: The present study demonstrates a higher efficacy achieved with lower secondary needling rates in deeper implant positions in conjunctiva after XEN-GGM.

Effective treatment of a normal-tension glaucoma patient with bilateral ab externo XEN Gel Stent implantation

“… 27 Most importantly for NTG patients, this approach allows for consistent sub-Tenon's stent placement, which has been shown to result in greater IOP reduction. 30 The mechanism for greater IOP reduction of sub-Tenon's placement is unknown, though perhaps the scleral vasculature is more effective at draining fluid or the healing response in the sub-Tenon's space is more conducive for developing diffuse posterior blebs that facilitate better drainage. Additionally, Tenon's can be separated from the episclera creating a pocket of space to shape bleb morphology and ensure the stent is free and mobile.…”

<p>Surgical Approaches for Implanting Xen Gel Stent without Conjunctival Dissection</p>

“…This point was emphasized by Lenzhofer and colleges who reported performing primary needling in all cases during XEN implantation to ensure that the distal end of the stent was completely free and mobile in its layer of implantation. 15 Furthermore, attempting sub-Tenon's placement risks bleeding from the episcleral vessels and intra-Tenon's placement. Given the above, the authors of this paper advocate a more temporal incision in the cornea to ensure the needle of the injector enters the angle at, or close to, 12 o'clock.…”

Endophthalmitis nach Bindehautperforation eines Glaukom-Gelstentimplantates

“…Durch seine materielle Zusammensetzung ist der Gelstent so flexibel, dass er sich dem Widerstand der Konjunktiva hingibt, sodass das Perforationsrisiko der Konjunktiva theoretisch minimal ist [4]. Im Vergleich zur Trabekulektomie zeigen sich nach Implantation des Gelstents durch die geringere Invasivität weniger postoperative Komplikationen und eine schnellere postoperative Wundheilung [5,6].…”

“…Diskussionswürdig ist zudem eine Subtenonimplantation des Stents, um perioperative Mikrotraumata der Konjunktiva auszuschließen. Eine aktuelle Studie berichtet, dass bei einer Intraund Subtenonlage des Gelstents, die als gleichwertig aufgeführt werden, niedrigere intraokulare Drücke im Vergleich zur Gruppe mit einem subkonjunktival gelegenen Stent ermittelt werden konnten [6]. Außerdem war die Revisionsrate mittels Needling bei einer Intra-und Subtenonlage des Gelstents geringer als bei einer subkonjunktivalen Lage [6].…”

“…Eine aktuelle Studie berichtet, dass bei einer Intraund Subtenonlage des Gelstents, die als gleichwertig aufgeführt werden, niedrigere intraokulare Drücke im Vergleich zur Gruppe mit einem subkonjunktival gelegenen Stent ermittelt werden konnten [6]. Außerdem war die Revisionsrate mittels Needling bei einer Intra-und Subtenonlage des Gelstents geringer als bei einer subkonjunktivalen Lage [6]. Allerdings kann es eine Herausforderung sein, den Gelstent intraoperativ geplant sicher in eine Subtenon-oder Intratenonlage zu positionieren.…”