Retinal optical coherence tomography (OCT) has recently become a vital tool for clinicians and researchers in ophthalmology and, increasingly, in neurology. Optical coherence tomography is quickly and easily performed, well-tolerated by patients, and allows high-resolution viewing of unmyelinated axons and other retinal structures in vivo. These factors have led OCT to find favor as a method of quantifying neuroaxonal loss in multiple sclerosis (MS), and the increasing acceptance of the anterior visual pathway as a model to investigate MS in humans.In this short review, the authors discuss OCT findings in MS research, and the relationships of these structural findings with established functional outcome measures such as visual acuity and electrophysiological examinations. The utility of OCT in patients with acute optic neuritis is emphasized. Optical coherence tomography is a particularly powerful tool when the individual retinal layers are visualized and quantified following the segmentation of scans; this technique shows promise as a method for defining novel MS phenotypes.