Advances in neuroimaging of the visual pathways and their use in glaucoma

Recently developed neuroimaging techniques such as diffusion tensor (DT) magnetic resonance (MR) imaging, functional MR imaging (fMRI), and MR spectroscopy can be used to evaluate the microstructural integrity of white-matter fibers and the functional activity of gray matter. They have been widely employed to investigate various diseases of the central nervous system, and they can be useful tools for assessing the integrity and functional connections of the visual pathways and areas that play key roles in glaucoma. In vivo degeneration of the optic nerves can be noninvasively demonstrated by DT MR imaging. DT fiber tractography provides valuable information on the axonal density of postgeniculate fibers (optic radiation), and fMRI studies of patients with primary open-angle glaucoma (POAG) have demonstrated alterations involving the human visual cortex that are consistent with clinically documented losses of visual function. This article reviews some of the more recent data supporting the use of MR imaging techniques as reliable, noninvasive tools for monitoring the progression of human glaucoma.