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Jake Edward Radell, Sonal Dangda, Maria A Mavrommatis, Joseph F Panarelli; Bleb Morphology and Patient Outcomes in Sub-Tenon Xen Implantation. Invest. Ophthalmol. Vis. Sci. 2020;61(7):944.
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Initial outcome reports for Xen gel stent implantation surgery have varied, with some groups reporting high rates of bleb needling. Surgical methods of implantation have also varied between ab interno and ab externo (sub-Tenon) approaches. This study examined bleb morphology and rates of surgical success, as well as rates of bleb failure and needling following sub-Tenon Xen implantation.
Medical records of 24 patients (26 eyes) who underwent sub-Tenon Xen implantation from 8/2013-12/2018 were retrospectively reviewed. Postoperative intraocular pressure (IOP) and number of glaucoma medications were analyzed at 1, 3, 6, 9 and 12 months. Surgical success was defined as IOP<21 and ≥5 mmHg with IOP reduction ≥20% from baseline at 2 consecutive follow-ups (>3 months) without loss of vision or need for reoperation. Bleb morphology and characteristics were analyzed by anterior segment optical coherence tomography (AS-OCT, Topcon DRI OCT version 1.1.1).
92.3% (24/26) of eyes achieved surgical success (61.5% without medication, 30.7% with medication). Mean preoperative IOP was 28.1±7.8 mmHg on 3.5±0.9 glaucoma medications. Mean IOP at postoperative month 6 (n=24) and 12 (n=14) was 13.3±5.5 mmHg (p<0.01) and 13.4±2.4 mmHg (p<0.01) respectively, on 0.4±0.8 (p<0.01) and 0.2±0.4 (p<0.01) medications. Complications, all on postoperative day 1, included hypotony (27%) and hyphema (23%). 3 eyes (12%) required needling.In the early postoperative period (<3 months), bleb morphology was characterized by multiple sub-conjunctival microcysts. At intermediate (6-12 months) and late (>24 months) timepoints, bleb morphology was characterized by multiple internal parallel layers of aqueous flow and uniform patterns. Bleb height was higher in late and intermediate blebs than in early blebs. All functional blebs showed the presence of a posterior episcleral fluid (PEF) lake, which was taller in intermediate and late blebs. All failed blebs showed high reflectivity with absence of aqueous flow at the distal end of the stent.
The sub-Tenon (open) technique of Xen gel stent implantation can provide significant IOP control with favorable bleb morphology and a low rate of postop bleb needling. A diffuse PEF lake on AS-OCT is consistent with surgical success. Further research, including prospective study, is needed to determine whether the sub-Tenon approach outperforms other methods.
This is a 2020 ARVO Annual Meeting abstract.
Early bleb with microcysts and PEF lake
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