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

Abstract

PurposeTo evaluate, using optical coherence tomography‐angiography (OCT‐A), the vascular features of good bleb function after XEN gel implantation (XGI) for uncontrolled glaucoma.MethodsForty‐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).ResultsMean postoperative follow‐up was 7.5 ± 0.14 months; Group 1 and 2 IOP were 14.0 ± 2.5 and 25.3 ± 2.1 mmHg, 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).ConclusionSuccessful 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.

Confocal Microscopy and Anterior Segment Optical Coherence Tomography Imaging of the Ocular Surface and Bleb Morphology in Medically and Surgically Treated Glaucoma Patients: A Review

“…Recently, optical coherence tomography angiography (OCT-A) has been gaining a role in post-operative filtration bleb assessment. OCT-A provides, in a quick and non-invasive way, information about the bleb-wall vasculature that cannot be adequately explored with the available ophthalmologic imaging platforms [ 112 , 113 ].…”

“…Few studies have evaluated the relationship between filtering bleb vascularization at OCT-A and surgical success after glaucoma surgery ( Table 3 ) [ 112 , 113 , 114 , 115 , 116 ].…”

“…Finally, Mastropasqua et al [ 113 ] evaluated the filtration bleb features after XEN gel stent implantation using OCT-A. Successful filtration blebs presented a lower bleb wall vessel density and numerous and large areas of vessel displacement within the bleb wall.…”

“…Successful filtration blebs presented a lower bleb wall vessel density and numerous and large areas of vessel displacement within the bleb wall. The authors suggested that these OCT-A signs may be considered angiographic biomarkers of a good aqueous humour percolation through the bleb wall layers, which can help to distinguish functioning from non-functioning filtering blebs [ 113 ].…”

“…rarefied vascular network with low vessel density and numerous and large vessel displacement areas within the bleb-wall [ 113 ]…”