Evaluation of Bleb Morphology and Reduction in IOP and Glaucoma Medication following Implantation of a Novel Gel Stent

Abstract

Objective To evaluate the efficacy and safety of the Xen Gel Stent and provide a macro- and microscopic analyses of bleb morphology. Methods A prospective 12-month study on patients with primary open-angle glaucoma. Patients underwent implantation of the XEN Gel Stent (Allergan INC, Dublin, Ireland) either alone or combined with a cataract surgery. Biomicroscopy, in vivo confocal microscopy (IVCM), and anterior segment-optical coherence tomography (AS-OCT) were used to assess bleb morphology. Safety parameters were adverse events, best corrected visual acuity, visual field, and corneal endothelial cell loss. A postoperative IOP ≤ 18 mmHg without or on medications was respectively defined as complete and qualified success while an IOP ≥ 18 mmHg was defined as failure. Results Twelve eyes of 11 patients were evaluated. At one year, 5 out of 10 patients available achieved a complete success while five were qualified success. AS-OCT showed that bleb wall reflectivity was significantly higher in the failure group; IVCM revealed that stromal density was significantly lower in the success group. No safety issues were recorded. Conclusion Implantation of the XEN Gel Stent appears to be a safe and effective procedure. AS-OCT and IVCM may be helpful in bleb assessment.

Optical coherence tomography analysis of filtering blebs after long-term, functioning trabeculectomy and XEN® stent implant

“…It is clear that AS-OCT offers several advantages over slit lamp examination to accurately measure the bleb size or to evaluate the internal structures of the filtration blebs [9][10][11][12][13][14][15]. The filtering blebs obtained with the XEN Gel Stent® have previously been studied by AS-OCT [18], indicating that non-functioning blebs were flatter and with a higher bleb wall reflectivity. Well-functioning XEN blebs also had a low degree of reflectivity, although there was no control group in this earlier study, and no comparison with other filtering procedures or with a healthy conjunctiva was possible.…”

XEN Gel stent: A Review

“…The mean baseline IOP in prospective studies has been in the range of 16-25 mm Hg, with an IOP drop of 23-42% on 0.3-1.7 glaucoma medications at 1 year postoperatively. [12][13][14][15][16][17] Table 1 shows the comparative results of both the prospective and retrospective studies.…”

“…[20] In a study by Fea et al, the success rate was 40% at 36 months, with a 72% reduction in medications, across stand-alone XEN, and phaco-XEN. [17] Most of the above studies evaluated eyes with primary open angle glaucoma (POAG). Eyes with secondary open-angle glaucoma may have as good or potentially better success with the XEN gel stent.…”

“…[16,19] A post-operative needling rate of 2-50% and 22-51% has been reported in prospective studies and retrospective studies, respectively. [11][12][13][14][15][16][17][18][19][25][26][27] The time to initial needling/revision ranged from 6-582 days (median -59.5 days) and the median number of interventions was 2. [16,26] Smith et al, in their study on 68 eyes, noted a 70% qualified success rate in eyes which underwent bleb needling or revision.…”

“…[5] Studies utilizing the anterior segment optical coherence tomography (AS-OCT) have provided useful insights into the morphology of post-XEN gel stent blebs and have been helpful in the assessment of predictors for functionality. [17,32,33] De Gregorio et al noted the presence of subconjunctival microcysts near the implant at 12 months post-operative. [13] Olate-Pérez et al, in a study on 30 eyes with phaco-XEN, noted that blebs with cystic pattern and low reflectivity have better postoperative outcomes in terms of IOP at 12 months.…”