The Eye is a Window to the Soul: Understanding Central Nervous System Disorders through the Afferent Visual Pathway
The afferent visual pathway is a functionally eloquent region of the central nervous system (CNS). Cardinal features of many inflammatory, ischemic, and compressive CNS lesions can be appreciated through detailed ophthalmic examination, because these disorders cause vision loss, and damage to the optic nerve and surrounding retinal nerve fiber layer. Merits of the afferent visual pathway, as a putative CNS model, include the fact that patients seek medical attention when they experience visual disturbances, thus providing a timeline during which manifestations of injury and repair can be monitored. Moreover, there are standardized tests of visual function that allow deficits in both form and motion perception to be reliably quantified. The afferent visual system is highly elegant in terms of its topographical arrangement. In the modern imaging era, optical coherence tomography provides high-resolution measures of neuroaxonal integrity in the CNS, which can be followed longitudinally as markers of neuro-degeneration. Finally, the contributions of cortical adaptation to visual recovery can also be measured, using motion perception and sophisticated magnetic resonance imaging techniques. In this lecture, I will outline how the afferent visual pathway can be used to develop a structural – functional paradigm of CNS injury and repair with specific emphasis on demyelinating and compressive disorders.