Optic nerve head component analysis enters the clinic

Over the last decade, assessment of the optic nerve has blossomed not only as a means of evaluating the integrity of the anterior visual pathways but also as an indirect reflection of cortical and subcortical integrity in demyelinating and degenerative neurologic disease.^1,2 The bulk of research has involved optical coherence tomography (OCT), which utilizes low coherent light, much like an ultrasound, to measure the thickness of the retinal nerve fiber layer (RNFL), which contains the axons forming the optic nerve, and, more recently, the thickness of the macular ganglion cell layer, which contains the cell bodies of those axons.^3,4 Despite the many advantages of OCT, its weakness is that it fails to detect an acute lesion that has not yet altered the structure of the associated retinal components, or any nonstructural optic nerve dysfunction, for that matter. The visual evoked potential (VEP) measures the amplitude and delay of occipital electrical activity while one eye is subject to flashes of light, thus measuring the function of the optic apparatus more directly, but its ability to finely localize injury or to determine a specific etiology is limited.