Mechanisms of TBI and visual consequences in military and veteran populations

Blast-related (BR) traumatic brain injuries (TBIs) occur secondary to explosive blasts. Blast-related TBIs can be caused by the blast wave itself or by direct head trauma caused by events surrounding the blast. Non-blast-related (NBR) TBIs are caused by direct head trauma. Recent evidence shows that TBIs are associated with vision problems, particularly binocular system problems. The purpose of this study was to determine if similar types and amounts of vision problems are present in patients with BR TBIs and NBR TBIs.

A retrospective analysis of eye examination records of 50 NBR TBI and 50 BR TBI patients was conducted. Frequencies of visual symptoms and abnormal vision function measurements were computed and compared for the two patient groups.

More than 65% of NRB TBI and BR TBI patients reported vision problems. Reading complaints were found in approximately 50% of the patients. Light sensitivity was reported significantly more often in BR TBI patients (67%) than in NBR TBI patients (33%) (p < 0.01). Saccadic dysfunction was measured more often in NBR TBI patients (85%) than in BR TBI patients (58%) (p < 0.01). High rates of accommodative dysfunction and convergence insufficiency were also found, but the group differences were not significant. Strabismus, pursuit abnormalities, fixation defects, and visual field defects were also common in both groups.

For most findings, the mechanism of injury (NBR vs. BR) did not result in different frequencies or types of visual dysfunction. The reasons for finding higher frequencies of light sensitivity in the BR TBI group and saccadic dysfunction in the NBR TBI group are unknown, and further research is needed. Overall, the rates of vision complaints and oculomotor defects were high in both groups, indicating a need for a thorough eye examination for any patient with a history of TBI.