Course of the optic nerve fibers through the lamina cibrosa in human eyes

Background: This study investigated whether regional variations in the course of the optic nerve fibers through the lamina cribrosa may be one of the reasons why the local susceptibility for glaucomatous optic nerve fiber loss differs among the various regions of the optic disc. Methods: The study included 34 human eyes enucleated because of a malignant melanoma of the peripheral choroid without involvement of the anterior chamber angle or the optic nerve. Anterior-posterior sections through the pupil and the optic disc were histomorphometrically evaluated. In the central region and the peripheral part of the optic disc, we measured the thickness of the lamina cribrosa and the length of the lamina cribrosa ''channels'' through which the nerve fibers pass. Results: In the peripheral parts of the disc, compared with its central region, the lamina cribrosa was significantly thicker (P<0.0001, Wilcoxon test), the lamina cribrosa ''channels'' with the nerve fibers passing through were significantly longer (P<0.0001), and the ratio of length of the fiber ''channels'' to the thickness of the lamina cibrosa was significantly higher (P=0.0001). Conclusion: The lamina cribrosa is thicker and the course of the optic nerve fibers through the lamina cribrosa is more curvilinear in the disc pheriphery than in the disc center. These variations in the anatomy of the lamina cribrosa may be one of several factors influencing the regional susceptibility for glaucomatous optic nerve fiber loss within the optic nerve head.