Evaluation of Posterior Segment Structural and Vascular Changes After Gonioscopy-Assisted Transluminal Trabeculotomy

Background/Objectives: To evaluate longitudinal structural and vascular changes in the posterior segment following gonioscopy-assisted transluminal trabeculotomy (GATT) in primary open-angle glaucoma (POAG). Methods: This retrospective observational study included 36 eyes of 36 patients with POAG. Examinations were performed at baseline, at 1 week, and at 1, 3, and 6 months. Optical coherence tomography assessed macular layers and peripapillary retinal nerve fiber layer (RNFL) thickness. Enhanced depth imaging-OCT assessed choroidal thickness (CT). Optical coherence tomography angiography (OCTA) provided superficial and deep macular and peripapillary vessel density (VD). Longitudinal changes in visual acuity (VA), intraocular pressure (IOP), retinal and choroidal structure and microvasculature were evaluated. Results: Mean IOP decreased from 19.0 ± 8.3 mmHg to 15.0 ± 3.4 mmHg at 6 months (−20%; p = 0.002). VA showed a significant overall time effect (p = 0.005), characterized by a transient decline at week 1 and subsequent recovery, with no significant difference between baseline and month 6. RNFL thickness varied numerically across visits, without a significant overall time effect (p = 0.504). CT decreased at week 1 and approached baseline values by months 3–6, without a significant overall longitudinal change. No OCTA-derived microvascular parameter remained statistically significant after correction for multiple comparisons. No significant associations were found between IOP reduction and CT or RNFL changes, or between CT and OCTA parameters. Conclusions: GATT was associated with moderate IOP reduction, while no statistically significant short-term changes were detected in posterior segment structural and OCTA-derived microvascular parameters during the six-month follow-up.