Angiographic biomarkers of filtering bleb function after XEN gel implantation for glaucoma: an optical coherence tomography-angiography study.

Abstract

To evaluate, using optical coherence tomography-angiography (OCT-A), the vascular features of good bleb function after XEN gel implantation (XGI) for uncontrolled glaucoma. Forty-three patients (43 eyes), who underwent XGI, were enrolled. According to the intraocular pressure (IOP) reduction, patients were classified into Group 1 (21 eyes; success) and Group 2 (22 eyes; failure). Optical coherence tomography-angiography (OCT-A) was performed to image the vascularization of the conjunctival bleb-wall. The main outcomes were as follows: vessel displacement areas (VDAs), major vessel displacement area (MVDA; mm2 ), non-flow whole area (NFWA; mm2 ) and bleb-wall vessel density (BVD; %). Co-registered B-scans were also considered to evaluate the bleb-wall cyst-like structure density and area (BCSD, cysts/mm2 ; BCSA, mm2 ), and the bleb-wall thickness (BT, µm). Mean postoperative follow-up was 7.5±0.14months; Group 1 and 2 IOP were 14.0±2.5 and 25.3±2.1mmHg, respectively (p<0.001). Greater VDA (p<0.001), MVDA (p=0.046) and NFWA (p=0.001) values, and lower BVD (p<0.001) was found in Group 1 compared to Group 2. Group 1 showed higher BSCD, BSCA and BT values compared to Group 2 (p<0.001). Postoperative IOP positively correlated with BVD (r=0.567; p=0.003), but negatively with VDAs, MVDA (r=-0.581, p=0.002; r=-0.619, p=0.001, respectively), BCSD, BCSA (r=-0.580; p=0.002; r=-0.664; p<0.001) and BT (r=-0.627, p=0.001). Successful filtration blebs after XGI present numerous and large areas of vessel displacement within the bleb-wall, along with a rarefied vascular network. These OCT-A features can be considered angiographic biomarkers of a good aqueous humour percolation through the bleb-wall layers.