This multi-center VA study of visual function and structure in veterans after mild Traumatic Brain Injury (Palo Alto, Minneapolis and Iowa City VA Medical Centers), will address two main topic areas identified as priorities for the Chronic Effects of Neurotrauma Consortium (CENC): 1) Studies which focus on understanding neurosensory deficits associated with chronic mild Traumatic Brain Injury (TBI) and 2) Studies which assess diagnostics and prognostic measures for neural degeneration. The main aims of the grant are to prospectively study visual structural and functional consequences of mild traumatic brain injury (mTBI) in the eye and their connections in the brain to determine if progressive worsening occurs and to compare ocular and brain biomarkers of structure and function for diagnosis and prognosis. With this proposal, a more complete picture of the spectrum of visual sensory disturbances after mTBI will be obtained by utilizing more detailed tests of visual function and ocular motility, as well as newer structural analyses of OCT combined with functional MRI imaging of visual pathways in the brain (fMRI) and volume analysis of corresponding grey and white matter locations. We hypothesize that after mild TBI, structural and functional biomarkers of damage are more prevalent than previously appreciated in the eye and corresponding visual centers of the brain, providing the first evidence linking TBI-induced neural degeneration to eye and brain locations. Our second main hypothesis is that mild TBI and repeated episodes can cause a chronic progressive decline in eye and CNS biomarkers of vision in a subset of susceptible veterans. This is based on strong preliminary data from our own studies and that of our collaborators in humans and in established animal models of mild TBI, which show that acute injury initiates visual pathway damage, leading to a chronic, progressive process of neural degeneration. This proposal will have two Specific Aims - 1: Determine whether ocular functional and structural biomarkers after mild TBI significantly correlate with corresponding visual pathway biomarkers in the brain. 2: Determine whether ocular and corresponding location CNS biomarkers progress over time after mild TBI. Currently, it is not known if neuronal loss in the retina and brain after mTBI continues to progress over time. Closing this knowledge gap will be important for understanding and treating TBI-related visual symptoms and for establishing whether ocular biomarkers can be used to predict risk of CNS dysfunction and its progression over time.
An estimated 200-400 thousand veterans have suffered a traumatic brain injury (TBI) in the Iraq and Afghanistan conflicts. Many of them have visual symptoms as a result of their TBI, but to date, a longitudinal study using quantitative visual and brain measures has not been performed. This study will provide important information about the extent and progression of visual dysfunction present in mild TBI and to what extent there are also deficits present in brain networks. Our long-term goal is to design and test rehabilitative therapies aimed at strengthening impaired connections, through focal therapies. Potential therapeutic modalities include focal transcranial magnetic stimulation, visual behavioral tasks that may strengthen synaptic connections, chemical neuromodulation, and peripheral or central nerve stimulation.
