J Head Trauma Rehabil Vol. 30, No. 1, pp. 21–28 Copyright c  2015 Wolters Kluwer Health, Inc. All rights reserved. Differential Eye Movements in Mild Traumatic Brain Injury Versus Normal Controls David X. Cifu, MD; Joanna R. Wares, PhD; Kathy W. Hoke, PhD; Paul A. Wetzel, PhD; George Gitchel, MS; William Carne, PhD Objectives: Objective measures to diagnose and to monitor improvement of symptoms following mild traumatic brain injury (mTBI) are lacking. Computerized eye tracking has been advocated as a rapid, user friendly, and field-ready technique to meet this need. Design: Eye-tracking data collected via a head-mounted, video-based binocular eye tracker was used to examine saccades, fixations, and smooth pursuit movement in military Service Members with postconcussive syndrome (PCS) and asymptomatic control subjects in an effort to determine if eye movement differences could be found and quantified. Participants: Sixty Military Service Members with PCS and 26 asymptomatic controls. Outcome Measures: The diagnosis of mTBI was confirmed by the study physiatrist’s history, physical examination, and a review of any medical records. Various features of saccades, fixation and smooth pursuit eye movements were analyzed. Results: Subjects with symptomatic mTBI had statistically larger position errors, smaller saccadic amplitudes, smaller predicted peak velocities, smaller peak accelerations, and longer durations. Subjects with symptomatic mTBI were also less likely to follow a target movement (less primary saccades). In general, symptomatic mTBI tracked the stepwise moving targets less accurately, revealing possible brain dysfunction. Conclusions: A reliable, standardized protocol that appears to differentiate mTBI from normals was developed for use in future research. This investigation represents a step toward objective identification of those with PCS. Future studies focused on increasing the specificity of eye movement differences in those with PCS are needed. Key words: eye tracking, fixations, mild traumatic brain injury, postconcussion syndrome, saccades, smooth pursuit A S A RESULT of injuries to both military service members in combat and athletes in contact sports, there has been heightened focus on metrics to diag- nose and monitor recovery after mild traumatic brain injury (mTBI) and related sequelae. 1,2 A significant lim- iting factor in the diagnostic approach to mTBI has Author Affiliations: Departments of Physical Medicine and Rehabilitation (Drs Cifu and Carne) and Biomedical Engineering (Drs Wetzel and Gitchel), Virginia Commonwealth University; Physical Medicine and Rehabilitation Program Office of the Department of Veterans Affairs (Dr Cifu); and Department of Mathematics and Computer Science, University of Richmond (Drs Wares and Hoke), Richmond, Virginia. Funding was provided for the primary study by a Defense Advanced Research Projects Agency grant (N66001-09-2-206), US Navy Bureau of Medicine and Surgery for contract funding temporary duty requirements, and the US Army Medical Materiel Development Activity for end-of-study contract funding. The funding sources had no role in the study design, analysis, interpretation of the data, the writing of the paper, or the decision to submit the paper for publication. The views expressed herein do not necessarily represent the views of the Depart- ment of Veterans Affairs, Department of Defense, or the US Government. The authors declare no conflicts of interest. Corresponding Author: William Carne, PhD, Department of PM&R, Virginia Commonwealth University, 1223 East Marshall Street, Richmond, VA 23298 (lasile@aol.com). DOI: 10.1097/HTR.0000000000000036 been the dependence on self-report of injury and symp- toms, resulting in a provisional syndromic-based di- agnosis, postconcussion syndrome (PCS). Increasingly, there has been recognition that an mTBI is more accu- rately termed as a “potentially concussive event” (PCE), rather than a syndrome. 3–5 If specific criteria (eg, al- teration or loss of consciousness with associated mem- ory loss/amnesia surrounding the event) are confirmed, then the diagnosis of mTBI may be made. If these cri- teria are not met, then the PCE cannot be labeled as an mTBI, but may still manifest with symptoms related to secondary physical injury (eg, neck or skull-based mus- culature and other soft tissue) and psychological trauma (eg, acute stress reaction). It is more proper to apply the “syndrome” label only after the mTBI has been con- firmed and has manifest in a symptom complex that has persisted for more than 3 months after injury. 6 Im- portantly, even in the case of a confirmed mTBI, the effects of other physical and psychological conditions often contribute to the symptoms and syndrome. 5 The limitations of the current self-reported, subjec- tive accounting of traumatic events, symptoms, and improvements are manifold. Without objective doc- umentation of the PCE, such as pre-event neuropsy- chological screening, event videotaping, or data from Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. 21