Purpose of review
The arrival of large datasets and the on-going refinement of neuroimaging technology have led to a number of recent advances in our understanding of visual pathway disorders. This work can broadly be classified into two areas, both of which are important when considering optimal management strategies. The first looks at delineation of damage, teasing out subtle changes to (specific components of) the visual pathway, which may help evaluate severity and extent of pathology. The second uses neuroimaging to investigate neuroplasticity, via changes in connectivity, cortical thickness, and retinotopic maps within the visual cortex.
Here we give consideration to both acquired and congenital patients with damage to the visual pathway, and how they differ. Congenital disorders of the peripheral visual system can provide insight into the large-scale reorganisation of the visual cortex: these are investigated with reference to disorders of the optic chiasm and anophthalmia (absence of the eyes). In acquired conditions, we consider recent work describing patterns of degeneration, both following single insult and in neurodegenerative conditions. We also discuss developments in functional neuroimaging, with particular reference to work on hemianopia and the controversial suggestion of cortical reorganisation following acquired retinal injury.
Techniques for comparing neuro-ophthalmological conditions with healthy visual systems provide sensitive metrics to uncover subtle differences in gray and white matter structure of the brain. It is now possible to compare the massive reorganisation present in congenital conditions with the apparent lack of plasticity following acquired damage.