Long-Term Shape, Curvature, and Depth Changes of the Lamina Cribrosa after Trabeculectomy

Abstract

To evaluate changes in lamina cribrosa (LC) shape, curvature, and depth after trabeculectomy. Prospective, observational case series. A total of 112 patients (118 eyes) with open- or closed-angle glaucoma undergoing trabeculectomy. The optic nerve head was imaged using enhanced depth imaging spectral-domain OCT before trabeculectomy and at 6 follow-up visits throughout the first postoperative year. The anterior LC surface and Bruch's membrane opening were marked in the serial horizontal B scans for the analysis of LC parameters using Morphology 1.0 software. Postoperative morphologic LC changes were assessed. The postoperative LC global shape index (GSI), nasal-temporal (N-T) and superior-inferior (S-I) curvatures, and mean and sectoral LC depth (LCD). The mean LC GSI increased only during the early postoperative period (P= 0.02), resulting in a change toward the saddle-rut shape. There was a flattening of the LC curvature in N-T (P < 0.001) and S-I (P= 0.003) meridians 12 months after trabeculectomy. A shallowing of the mean and sectoral LCD from baseline was significant throughout the entire follow-up period (P < 0.001) and progressed up to postoperative month 6. Twenty-eight patients showed a deepening of the LC from baseline in at least 1 visit. Eyes with shallower LCD compared with baseline responded to intraocular pressure (IOP) reduction with greater movement anteriorly than eyes with deeper LCD (P= 0.002). Greater IOP reduction (P= 0.007), less retinal nerve fiber layer thinning over the year (P= 0.003), and more superiorly-inferiorly curved baseline LC (P= 0.001) were associated with an increase in GSI. Younger age and IOP reduction were related to LC shallowing (P < 0.001, P= 0.002) and N-T flattening (P < 0.001). In most eyes, trabeculectomy resulted in long-term flattening and shallowing of the LC. However, in some eyes, LC deepened from baseline. Change in LC global shape appeared to be temporal. Reduction in IOP plays an important role in the early phase of LC change; however, in the later phase, LC remodeling may play a crucial role in view of stable IOP.