The application to MS of nonconventional MRI techniques such as magnetization transfer imaging, magnetic resonance spectroscopy, and diffusion tensor imaging, has led to modest achievements in linking imaging data with clinical measures of disease severity.7 However, despite these improvements, until recently the progress in coupling specific clinical syndromes in MS with pathological changes within discrete tract systems was limited.8, 9, 10 This Review describes a number of advancements in the application of optical coherence tomography (OCT), a technology that enables objective analysis of the processes of neurodegeneration within a highly discrete and eloquent CNS structure retina. OCT enables investigators to rapidly and reproducibly evaluate the structural composition of the retina and to provide unique insights into this structure. While already validated for the longitudinal assessment of glaucoma11, 12 and macular degeneration,13 OCT is currently being investigated for its