PURPOSE. To determine microvasculature changes in the deep optic nerve head (ONH) and peripapillary tissues after trabeculectomy, and to correlate these with changes in the lamina cribrosa (LC) curvature. METHODS. Fifty-six eyes with primary open-angle glaucoma that underwent trabeculectomy were included. The optic nerve and peripapillary microvasculature were evaluated in en face images obtained using optical coherence tomography (OCT) angiography (OCTA) before and 3 months after trabeculectomy. The OCTA-derived vessel density (VD) was calculated in each layer segmented into the prelaminar tissue (PLT), LC, peripapillary retina (PR), and peripapillary choroid (PPC). Swept-source OCT volume scanning of ONH was performed on the same day as OCTA to examine the change in LC curvature quantified as the LC curve index (LCCI). RESULTS. At 3 months postoperative, the IOP and LCCI had significantly decreased (both P < 0.001). OCTA images revealed a significant increase in VD in the LC (P ¼ 0.006), but not in the PLT, PR, or PPC. Twenty-six eyes showed both significant LCCI decrease and VD increase based on 95% Bland-Altman limits of agreement. The VD increase in the LC was significantly associated with larger percentage reductions in IOP (P ¼ 0.040) and LCCI (P < 0.001) in the univariate analysis. Multivariate analysis revealed that only the LCCI reduction was a significant factor affecting the VD increase in the LC. CONCLUSIONS. A significant increase in VD was observed at the level of the LC after trabeculectomy. The VD increase was more strongly associated with the reduction in the LC curvature than with the reduction of IOP.