Mechanisms of TBI and visual consequences in military and veteran populations.

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Visual impairment and dysfunction in combat-injured servicemembers with traumatic brain injury.

PURPOSE: The purpose of this study was to determine the frequencies of visual impairment and dysfunction among combat-injured Polytrauma Rehabilitation Center (PRC) inpatient and Polytrauma Network Site (PNS) outpatient military personnel with traumatic brain injury (TBI). METHODS: A retrospective analysis of data from vision screenings of 68 PRC-inpatients with moderate to severe levels of TBI and 124 PNS-outpatients with mild TBI at the VA Palo Alto Health Care System was conducted. RESULTS: Eighty-four percent of PRC-inpatients and 90% of PNS-outpatients had TBIs associated with a blast event. The majority of patients in both the PRC and PNS populations had visual acuities of 20/60 or better (77.8% PRC, 98.4% PNS). Visual dysfunctions (e.g., convergence, accommodative, and oculomotor dysfunction) were common in both PRC and PNS populations. In the PRC-inpatient population, acuity loss of 20/100 to no light perception (13%) and visual field defects (32.3%) were found. In the PNS-outpatient population, acuity loss of 20/100 to no light perception (1.6%) and visual field defects (3.2%) were infrequently found. In both the PRC and PNS populations, visual field defects were more often associated with blast than non-blast events. CONCLUSIONS: Blast events were the most frequent mechanism of injury associated with TBI in combat-injured servicemembers. The vision findings suggest that combat troops exposed to blast with a resulting mild TBI are at risk for visual dysfunction, and combat troops with polytrauma injuries are at risk for visual dysfunction and/or visual impairment. The visual consequences of such injuries necessitate further study and support the need for appropriate evaluation and treatment in all severities of TBI.