The Potential Utility of Retinal Biomarkers to Index Central Nervous System Effects of Repetitive Blast Exposure in Military Personnel.

Military personnel exposed to blasts receive repeated subconcussive head impacts. Although these events typically do not cause immediate symptoms and do not lead to medical evaluation, the cumulative effects of subconcussive impacts can be significant and can include postconcussive symptoms, changes in brain structure and function, long-term cognitive dysfunction, depression, and chronic traumatic encephalopathy. Retinal measures such as thickness of retinal neural layers, density of retinal microvasculature, and strength of retinal neuronal firing are associated with cognitive function and brain structure and function in healthy populations and in neurodegenerative disease cohorts, and changes over time in retinal indices predict cognitive decline and brain atrophy in longitudinal studies in a range of medical populations. This commentary highlights the potential benefits of using retinal biomarkers in the routine screening and monitoring of brain health in warfighters and veterans. Retinal measures can be rapidly acquired (often in a matter of seconds) using methods that are inexpensive and noninvasive, and they can be collected with movable and often portable equipment that uses automated scoring routines that can be used for prediction and decision-making at the individual level. To date, however, retinal biomarkers have not been included in studies of blast overpressure exposures in military personnel. Despite this, preclinical and human evidence suggests that they could be among the most effective methods for tracking central nervous system damage in people exposed to repeated blasts. Retinal biomarkers could also contribute to brief test batteries to determine who is most at risk for long-term negative effects of future exposures. In addition, the sensitivity of retinal indices to blast exposure and mild traumatic brain injury suggests that they should be incorporated into research on strategies to minimize or prevent blast-related short- and long-term central nervous system changes in blast-exposed military personnel.