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Paul Wetzel, Ross Pallansch, George Gitchel, David Cifu; The Effect of Combat-Related Mild TBI on Saccadic Eye Movements. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1922.
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© ARVO (1962-2015); The Authors (2016-present)
Mild Traumatic Brain Injury (mTBI) among combat personnel deployed in conflict areas of the Middle East has significantly increased due to exposure to explosive blasts. These injuries can lead to physiological and psychological effects including oculomotor deficits. Last year we presented results on the effects of mTBI on eye movements during reading (Wetzel, et al. ARVO 2012). The aim of this study is to examine the effects of mTBI on saccadic response during horizontal (H) and vertical (V) tracking as a further objective measure of mTBI.
In an ongoing double-blind study, the eye movements of 60 active duty Marines (20 to 34 yrs) diagnosed with mTBI from 3 to 24 months before initial measurement and a control group (n = 6) from 18 to 21 years were binocularly recorded with stabilized head at 500 Hz (SR Research). In separate trials, participants were instructed to track spatially and temporally randomized step changes in target position along the H and V axes. The eye movements of the Marines were recorded before assignment to one of 3 treatment categories: Hyperbaric Oxygen Therapy at one of two treatment levels and a sham condition. Within 2 weeks of completing treatment, the Marines were retested (n = 31) and were tested again after roughly 3 months (n = 30). Data were analyzed for response latency, number of saccades, saccadic amplitude, duration, velocity and acceleration, including position accuracy and fixation stability. Statistical analysis was performed on all eye measurement parameters using ANOVA.
While dissimilarities persist in all eye movement parameters, significant dissimilarities were found in both the H and V stimuli group. Differences in saccadic duration were not significant for H saccades but were for V saccades. Peak velocities for H saccades were significantly slower for mTBIs compared to controls. In both stimulus directions, significant differences were found in both peak acceleration and deceleration. The number and mean saccadic amplitude between controls and mTBIs were not significant. Fixation RMS velocity in controls was significantly less implying less stable fixation for those with mTBI. Within the mTBI group, V data was more likely to show potential treatment effects compared to H data.
Combat-related mTBI produces similar but unequal effects on saccadic response in both the H and V directions. Fixation stability may also be an important indicator of mTBI status.
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