Histopathological findings of failed blebs after microinvasive bleb surgery with the XEN Gel Stent and Preserflo MicroShunt

Abstract

Purpose: The success of XEN Gel Stent (XEN) and Preserflo MicroShunt (Preserflo) implantation depends mainly on the development of bleb fibrosis. This study aimed to describe the histological findings of bleb fibrosis after XEN and Preserflo surgery.

Methods: This retrospective study included patients with different types of glaucoma who underwent revision surgery after XEN or Preserflo implantation. The available clinical information and histological samples of removed fibrotic tissue were analyzed.

Results: Thirty-six patients were included. Revision surgery was performed at a median of 195 (range = 31-1264) days after primary surgery. The mean intraocular pressure changed from 29.1 (± 10.3) mmHg at baseline to 18.3 (± 8.7) mmHg (- 37%; p < 0.0001) and 16.2 (± 4.2) mmHg (- 45%; p < 0.0001) after 6 and 12 months, respectively. Histological analysis revealed an increase in activated fibroblasts and macrophages in all specimens and a parallel orientation of fibroblasts in a minor part of the probe in 60% of the specimens. No pronounced inflammatory reaction in the form of lymphocytic or granulocytic infiltration was observed. The comparison of specimens from uveitic glaucoma and primary open-angle glaucoma patients revealed no significant differences.

Conclusions: The histological analysis of fibrotic blebs from the XEN and Preserflo implants did not show any pronounced immune or foreign-body reaction and revealed a similar histological pattern of failed blebs after trabeculectomy.

Keywords: Bleb fibrosis; Filtering surgery; Gel stent; Histology; Microinvasive bleb surgery; Microinvasive glaucoma surgery; Microshunt.

Fig. 1

a Mean intraocular pressure after bleb revision. Whiskers represent standard deviations. ^****p < 0.0001. b Mean number of glaucoma medications taken after bleb revision. ^*p < 0.05

Fig. 2

Microphotographs of fibrotic tissue from revision surgery after failed Preserflo MicroShunt implantation. a Two different tissue types are seen in this hematoxylin and eosin staining: tight connective tissue (star) and loose connective tissue (arrow). Blood vessels (arrowhead) are predominantly present within the loose connective tissue area. b Immunohistochemical staining for macrophages shows that the CD68-positive macrophages (red) are predominantly seen within the loose connective tissue area (arrow) of the specimen in comparison to the tight connective tissue area (star). c Immunohistochemical staining for sm-actin (red color) highlights myofibroblasts in the tight connective tissue area (star). In the loose connective tissue area, only myofibroblasts around blood vessels are stained (arrow). d Immunohistochemical staining for vimentin (red) demonstrates multiple fibroblasts predominantly in an irregular configuration in the loose connective tissue area (arrow) and a more parallel orientation in the tight connective tissue area (star)

Fig. 3

Microphotographs of fibrotic tissue from revision surgery after failed XEN Gel Stent implantation. a Predominant tight connective tissue area (star) and predominant loose connective tissue area (arrow) where most blood vessels (arrowhead) are present in this hematoxylin and eosin staining. b Immunostaining for CD68 highlights only few macrophages in the fibrotic tissue (red). c Immunohistochemical staining for sm-actin (red) demonstrates myofibroblasts within the tight connective tissue area (star). In the loose connective tissue area (arrow), sm-actin is expressed only in the blood vessel-associated myofibroblasts (arrowhead). d Immunostaining for vimentin (red) shows multiple fibroblasts in a predominantly irregular arrangement throughout the tissue specimen