Neural Pathways and Optic Nerve: Dementia, Glaucoma and Injury

Background     As much as 20 percent of the brain is related to direct sight tasks and 50 percent is involved in vision-related neuroprocessing. The retina is a direct extension of the brain. Neurodegenerative diseases and injury to the brain impact the retina and age-related diseases originating in the eye result in measureable structural losses of brain structure.  With newer imaging technologies we are gaining a greater knowledge of the structural functional relationships in the visual system.  With this understanding we will be better able to guide treatment and rehabilitation as well as prevention.

Methods     While the emphasis will be on glaucoma, other neurodegenerative processes impacting vision  will be discussed such as injury and Alzheimer’s disease.  The dynamics of brain structure, cerebral spinal fluid changes with injury or disease and implications for the eye will be reviewed.  Even in the absence of reduced acuities or field loss, patients experiencing injury can have substantial visual dysfunction.  This is particularly compelling with the head injuries experienced by first responders or military or risks for falls after injury or stroke.  

Outcomes    The literature reports very early detriments to visual pathways with disease; even in the absence of cell death when using more dynamic imaging technologies such as Diffuse Tensor Imaging and retinal imaging technologies.

Conclusions    Tasks such as safe mobility and reading are often demonstrating deficits with disease or injury.  A knowledge of where the structural damage within the brain has occurred will enable more focused therapies and a better understanding of prognosis.