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Open Conjunctival Approach for Sub-Tenon's Xen Gel Stent Placement and Bleb Morphology by Anterior Segment Optical Coherence Tomography.

PRECIS
Sub-Tenon's implantation of the Xen® Gel stent resulted in significant intraocular pressure lowering along with a low rate of postoperative bleb needling, and a favorable bleb morphology on anterior segment optical coherence tomography.


PURPOSE
To assess clinical outcomes and bleb morphology following sub-Tenon's implantation of the Xen® Gel Stent (Allergan Inc., Dublin, Ireland).


METHODS
The medical records of patients who underwent sub-Tenon's Xen® Gel Stent implantation with intraoperative mitomycin-C via an open conjunctival approach were reviewed. Postoperative intraocular pressure (IOP) and number of glaucoma medications at 1,3,6,9 and 12 months were assessed. Bleb morphology was analyzed at various timepoints using anterior segment optical coherence tomography (AS-OCT, Topcon DRI OCT version 1.1.1).


RESULTS
Twenty-six eyes were included in the study. Mean age was 69.4±8.0 years. Mean preoperative IOP was 28.1±7.8▒mm Hg on an average of 3.5±0.9 glaucoma medications. Mean IOP at postoperative month 12 (n=23 eyes) was 12.9±4.0▒mm Hg (P<0.01) on an average of 0.3±0.6 (P<0.01) glaucoma medications. Three eyes (12%) required postoperative needle revision. Bleb morphology in the early postoperative period (≤ 3▒mo) was characterized by multiple small subconjunctival microcysts on AS-OCT. At the intermediate (6-12▒mo) and long-term (>12▒mo) time points, reduction in microcysts with multiple internal parallel layers of aqueous flow and a uniform pattern were more frequently noted. All functional blebs were characterized by the presence of a posterior episcleral fluid lake. Failed blebs showed absence of aqueous humor around the distal end of the microshunt.


CONCLUSION
Following an open conjunctival approach, sub-Tenon's placement of the Xen® Gel Stent with significant IOP lowering was achieved. In eyes with good shunt function, bleb morphology by AS-OCT showed a posterior episcleral fluid lake similar to findings following trabeculectomy.