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

Purpose The purpose of this study was to use Triton (R) SweptSource OCT to evaluate the morphology of blebs formed when eyes are treated with XEN (R) implants and to compare these with the blebs in successfully functioning eyes after trabeculectomy (TB) and with eyes of healthy controls. Methods A cross-sectional, observational study. We analyzed 25 eyes, 15 after TB and 10 with XEN (R) implants, comparing them with 23 healthy eyes (controls). We evaluated the conjunctival morphology of the eyes using AS-OCT. The main parameters evaluated were bleb height, sub-epithelial fibrosis, epithelial thickness, and changes in intraocular pressure (IOP). Results We found that the filtering blebs formed in eyes in which a XEN (R) stent was implanted were significantly flatter (bleb height 417 +/- 183 mu m) than the blebs formed in TB eyes (bleb height 618 +/- 256 mu m, p < 0.05). Moreover, sub-epithelial fibrosis did not develop in any of the blebs produced by the XEN stent, whereas some fibrosis was evident in 40% of the blebs that formed after TB (p < 0.05). The epithelium was thicker when the XEN implant was used (65 +/- 18.5 mu m) than when eyes underwent TB (60 +/- 17.7 mu m), and it was thicker than in control eyes (51 +/- 9.7 mu m, p < 0.05). Moreover, the decrease in the IOP induced by the XEN (R) stent (-8.5 +/- 5.3 mmHg) was similar to that produced by TB (-8.8 +/- 5.2 mmHg, p > 0.05). Conclusions Filtering blebs obtained after the introduction of a XEN (R) stent were morphologically distinct to those produced by TB, and they are more similar to the healthy conjunctiva.