Traumatic brain injury (TBI) is one of the invisible wounds of war, and one of the signature injuries of troops wounded in Afghanistan and Iraq. It is estimated that between 10-20% of Iraqi veterans, or 150,000 - 300,000 persons have some level of TBI. Visual symptoms are a common sequelae of TBI. Very little is known about the chronic visual consequences of mild TBI, its progression, and its correlation with central nervous system (CNS) deficits. Currently, it is not known if neuronal loss in the retina and brain after mTBI continues to progress over time.
Closing this knowledge gap is 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. The purpose of this study is to identify the spectrum of visual sensory disturbances after mTBI by utilizing more detailed tests of visual function and ocular motility, as well as newer structural analyses of optical coherence tomography (OCT) combined with functional MRI imaging of visual pathways in the brain and volume analysis of corresponding grey and white matter locations.
This 3-year, prospective, case-control study of veterans will evaluate the consequences of mild TBI on the visual pathways in the eye and brain over time. Two main veteran cohorts with mild TBI and without TBI will be studied, and we will analyse visual function, eye movement and pupil recordings, and OCT imagining. An estimated 200-400 thousand veterans have suffered a 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 mTBI 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 and central nerve stimulation.