A provocative and overly reductive mantra is that "the back of the eye is the front of the brain". Retinal imaging techniques that take advantage of this "window" to the central nervous system can provide valuable information regarding injury to the nervous system with relative ease and with a limited burden to patients. The retina develops embryonically as part of the neuroectoderm, is made up principally of neurons and their supporting cells, and is synaptically tied to the central nervous system (CNS). This has led to significant interest in using retinal health as a biomarker for brain health-given the relatively limited accessibility of brain tissue in chronic neurodegenerative diseases that progress over decades. The retina is not truly part of the CNS, and as with much of brain imagingthe grounds for asserting the pathological specificity of retinal imaging is limited. Biophotonics-based methods such as optical coherence tomography indirectly provide an opportunity to evaluate retinal neurodegeneration, while autopsy studies, histology and immunohistochemistry predominate as the methods that collect direct pathological data. Our understanding of pathological retinal lesions characteristic of demyelinating diseases, specifically diseases showing anterior visual pathway involvement, has grown significantly in recent years.

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