Reading speed, visual deficits, and cerebral white matter integrity in veterans with and without mild traumatic brain injury.

Introduction: Since 2001, approximately 17.3% of enlisted personnel have experienced a traumatic brain injury (TBI) according to the United States military. Visual deficits (e.g., convergence insufficiency or pursuit abnormalities) are reported as chronic, persistent symptoms of TBI, which can impact daily activities such as reading, computer work, and driving. Methods: In the present study, diffusion-weighted imaging (DWI) data and behavioral and survey data related to visual function were analyzed for 63 combat veterans with and without mild TBI (mTBI). We also tested the hypothesis that white matter damage, measured as either decreased fractional anisotropy of white matter or "potholes" evident in the DWI data, would predict visual behaviors (reading speed, smooth pursuit catch-up saccades, and/or convergence insufficiency). Results: Our key finding is that scores on the Convergence Insufficiency Symptom Survey (CISS) predicted whether the use of a color overlay would increase reading speed for participants with mTBI, but not for control participants. General linear model analyses found a relationship between smooth pursuit catch-up saccades and the cumulative number of white matter "potholes" found in white matter across the cerebrum. However, the sample size was too small to conclude that these correlations were uniquely related to TBI status. Discussion: These findings point toward the importance of additional research to determine exactly how mTBI is associated with reduced reading speed and why altering the color of the page improves performance for individuals with mTBI and convergence insufficiency.