PURPOSE. To investigate whether the lamina cribrosa (LC) curvature is decreased after trabeculectomy. METHODS. Thirty-nine eyes of 39 patients with primary open-angle glaucoma who underwent trabeculectomy were included. Optic nerves were scanned by using enhanced-depth-imaging spectral-domain optical coherence tomography before and after trabeculectomy. The LC curvature was assessed by measuring the LC curvature index (LCCI) in seven horizontal B-scan images in each eye. RESULTS. The LCCI was significantly smaller at postoperative 6 months than at the preoperative level in all seven planes (all P < 0.001). Preoperative LCCI was associated with younger age at superior midperiphery, midhorizontal plane, inferior midperiphery (all P < 0.005) and higher preoperative intraocular pressure (IOP) at superior and inferior midperiphery (both P = 0.039). Younger age and larger preoperative LCCI were associated with a larger reduction of the LCCI at all three locations (P = 0.003 and 0.031 at superior midperiphery, P = 0.011 and 0.001 at midhorizontal plane, and P = 0.014 and 0.005 at inferior midperiphery, respectively), whereas the percentage lOP lowering was associated at superior and inferior midperiphery (P = 0.017 and 0.047, respectively). CONCLUSIONS. Lamina cribrosa curvature was reduced after trabeculectomy. This finding suggests that LC curvature may have value as a parameter relevant to optic nerve head biomechanics.