Exploring Structural and Vascular Changes of the Optic Nerve Head After Trabeculectomy in Primary Open-Angle Glaucoma

Background: Trabeculectomy remains gold-standard surgical approach for intraocular pressure (IOP) control in glaucoma, yet its impact on optic nerve head (ONH) morphology and retinal microvasculature has not been fully clarified. This study aimed to investigate structural and vascular changes of the ONH and macula after trabeculectomy using spectral-domain optical coherence tomography (SD-OCT) and OCT angiography (OCTA). Methods: In this retrospective study, data from 22 patients with primary open-angle glaucoma who underwent uncomplicated trabeculectomy were reviewed. The fellow eye served as control. Structural parameters, including Bruch’s membrane opening (BMO), maximum cup depth (MCD), and cup area, were measured with SD-OCT. Vessel density (VD) of the optic disc, peripapillary retina, and macular superficial (SCP) and deep (DCP) capillary plexuses were analyzed with OCTA. Preoperative and two-month postoperative data were compared using paired statistical tests. Results: Mean IOP decreased from 23.1 ± 3.9 mmHg to 13.2 ± 3.2 mmHg (p < 0.001). Significant postoperative reductions were observed in BMO (−5 ± 6%, p = 0.004), MCD (−31 ± 8%, p < 0.001), and cup area (−44 ± 18%, p < 0.001). RNFL thickness and ONH vascular parameters remained stable. In contrast, DCP vessel density increased in the foveal (p = 0.002) and parafoveal (p = 0.023) regions, while SCP density showed no significant change. Conclusions: Trabeculectomy was associated with measurable reversal of optic disc cupping, indicating partial structural recovery of the ONH following IOP reduction. The selective improvement in deep retinal vessel density suggests a layer-specific microvascular response. These findings provide further insight into the interplay between mechanical and vascular mechanisms in glaucoma and may inform postoperative monitoring strategies.