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

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 (−54% versus −19%, p < 0.001), week 2 (−39% versus −21%, p = 0.02), month 1 (−42% versus −28%, p = 0.035) and month 12 (−39% versus −24%, p = 0.024). The mean absolute IOP was lower in intra‐ and subtenon group at week 1 (10.8 [95%CI, 8.8–14.1] versus 16.6 [95%CI, 14.1–19.0] mmHg, p < 0.001) and months 12 (13.9 [95%CI, 12.4–15.4] versus 16.7 [95%CI, 14.6–18.8] mmHg, p = 0.041). At month 6, a lower burden for IOP‐lowering medication was shown for the intra‐ and subtenon group (0.2 ± 0.5 versus 1.0 ± 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 ± 1.7 versus 1.2 ± 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.