Changes in peripapillary and macular vascular measured using optical coherence tomography angiography after glaucoma drainage device procedures

Abstract

<strong>Purpose:</strong> <br/> This study aimed to evaluate changes in retinal vessel density (VD) and associated structural parameters in the macular and optic disc regions during the follow-up period after Paul glaucoma implant (PGI) surgery using optical coherence tomography angiography (OCTA). In addition, it sought to explore potential mechanisms of intraocular perfusion regulation, its relationship with retinal structure and function, and the associations between VD changes and systemic as well as intraocular physiological parameters. <br/> <strong>Methods:</strong> <br/> Patients with glaucoma who underwent PGI surgery were included. VD changes in the macular and peripapillary regions were assessed using 3 × 3 mm and 6 × 6 mm OCTA scans. Additional parameters, including retinal nerve fiber layer (RNFL) thickness, foveal avascular zone (FAZ) area and perimeter, visual field indices (mean deviation [MD] and pattern standard deviation [PSD]), and preoperative and postoperative intraocular pressure (IOP), were collected over a 6-month follow-up period. Linear regression analyses were performed to investigate the associations between VD and related clinical and physiological factors, aiming to determine the sensitivity of different retinal regions to local perfusion regulation. <br/> <strong>Results:</strong> <br/> During postoperative follow-up, macular VD showed a significant overall increase, whereas VD changes in the optic disc region were more heterogeneous, with limited improvement or slight decreases in certain areas. Among macular subregions, the parafoveal region demonstrated the most pronounced VD changes. Both intertemporal comparisons and linear regression analyses revealed that parafoveal VD was significantly correlated with the greatest number of independent variables, exceeding correlations observed in the perifoveal, optic nerve head (ONH), and peripapillary regions. High-resolution 3 × 3 mm OCTA scans proved more sensitive in detecting subtle postoperative perfusion changes, particularly in capturing perfusion dynamics within the fovea and its surrounding dense capillary network. FAZ area and perimeter were significantly reduced at 3 months postoperatively, indicating improved macular perfusion; partial recovery was observed at 6 months, although values remained below baseline, suggesting a prolonged perfusion adjustment process. RNFL thickness exhibited a transient increase at 1 week postoperatively, likely related to postoperative inflammatory responses, and returned to baseline by 6 months with minor regional fluctuations. Postoperative IOP decreased significantly and remained consistently lower than baseline throughout follow-up, whereas visual field parameters (MD and PSD) showed no significant improvement, with some patients demonstrating gradual progression consistent with the irreversible nature of glaucomatous damage. <br/> <strong>Conclusions:</strong> <br/> Following PGI surgery, macular VD increased significantly, while VD changes in the ONH and peripapillary regions were more complex and limited. Parafoveal VD was found to be particularly sensitive to dynamic intraocular perfusion regulation, underscoring its clinical analytical value. OCTA effectively captures postoperative retinal microvascular alterations and provides important insights into perfusion status and structure–function relationships. Further studies with longer follow-up periods and multicenter designs are warranted to clarify the long-term microvascular effects of PGI surgery.