Project Summary Acute brain injury (ABI) has a high mortality, largely driven by the early withdrawal of life-sustaining therapies during hospitalization. This critical decision is influenced by whether patients remain unresponsive after brain injury. Observing eye tracking to different visual stimuli is an important part of clinical examination to determine the conscious state and the potential for recovery of consciousness. However, eye tracking assessments are examiner dependent, and can misclassify up to 40% of unresponsive patients with preserved awareness, or covert tracking. The recent development of eye tracking technology provides sufficient temporal and spatial fidelity to make an informed assessment on patients' ability to track visual stimuli. Quantitative assessments of eye tracking to different visual stimuli have not been studied in the intensive care unit (ICU), shortly after injury, when clinicians discuss the patients' goals of care with families. Our preliminary data provide the scientific premise and the feasibility of using eye-tracker glasses in the ICU as a biomarker to detect covert tracking after ABI. We hypothesize that the detection of eye tracking using eye-tracker glasses, during the ICU stay may serve as a biomarker to identify covert tracking in patients who are unresponsive but who may have a better prognosis. In this study, we propose using a novel approach shortly after severe brain injury using the COVERT test (COvert Volitional Eye Response Test). We will assess 50 unresponsive ABI patients at two institutions using a 3-minute eye tracking experiment to mirror, moving stripes, and a bright colored object via the eye-trackers. The experiment will be done twice a day on days 3, 7, 10, and 14 post injury. The clinical team will be surveyed on whether the patient is tracking or not based on their clinical assessment. We will also obtain an electroencephalogram on day 7 to evaluate the thalamocortical integrity and correlate with the state of covert tracking. Using the COVERT test, we plan to identify covert tracking in unresponsive ABI patients using the eye- tracker glasses (Aim 1). We will also explore if covert tracking can predict recovery, using Glasgow Outcome Scale-Extended at 3-month follow-up after ABI (Aim 2). Results from this study have the potential to change the current prognostication paradigms in clinical practice after severe ABI using a novel quantitative approach using the eye-tracker technology that can assess tracking to visual stimuli to identify covert tracking.