Abstract
Purpose: :
To evaluate horizontal saccadic latency and accuracy in right and left gazes in subjects with traumatic brain injury (TBI) after combat blast exposure.
Methods: :
All subjects (34 blast TBI, 23 age and gender-matched controls) were part of an IRB-approved study. Written informed consent was obtained from the subject or authorized representative. All TBI subjects were injured in either Iraq or Afghanistan, and were assigned TBI levels based on initial Glasgow Coma Score, length of loss of consciousness or amnesia, and neuroimaging results. Mean age of both groups was 28 years. Video nystagmography (VerisEyes, Micromedical Technologies, Chatham, IL), using a lightweight mask with infrared cameras to track each eye, recorded responses to random saccades generated on a digital light bar. Accuracies were recorded as percentages and latencies in milliseconds. Non-parametric tests were used to compare TBI subjects and controls.
Results: :
Median saccadic latencies were significantly longer for TBI subjects than for matched controls (236 milliseconds vs. 223 milliseconds). Saccadic accuracy was poorer for TBI subjects than for matched controls, with TBI subjects marginally more likely to undershoot (median accuracy of 92% vs. 96% for controls). A significant difference was noted between the median deviation from target in the TBI group (9.4%) versus that of the control group (4.5%).
Conclusions: :
Saccadic latencies are significantly higher and accuracy is significantly lower in TBI subjects with blast exposure, compared with a matched comparison group by statistical analysis. Inaccuracy for TBI subjects is mainly in the form of undershooting the target, but some subjects demonstrated marked overshooting of the target. Horizontal saccadic abnormalities may contribute to reduced visual quality of life found in survivors of combat blast with TBI.
Keywords: eye movements: saccades and pursuits • visual impairment: neuro-ophthalmological disease • trauma