Objective: The eye may act as a surrogate for the brain in response to head acceleration during an impact. This paper reports the latest demonstration of the correlation between the passive human eye accelerations and the brain accelerations under head impacts using a model eye/brain/skull phantom. Approach: Experiments investigating rotational and linear accelerations were performed on a 3D-printed human head phantom, along with rotational experiments on a human volunteer. Data acquired during the passive eye response (PER) periods were processed and analysed using statistical methods including one-way normal analysis of variance, linear regression fit, and Pearson R correlation. Main results: The results have shown that, at least on the 3D-printed human head phantom, strong correlations can be found between the eye and the brain during the PER, which indicates a potential use of microelectromechanical systems inertial measurement units in real-time on-field monitoring and diagnosis of concussions or traumatic brain injuries. Significance: These discoveries pave the way for potential non-invasive wearable devices based on this technology to be applied in real-time on-field concussion monitoring, which is expected to provide vulnerable parties with instant alert thus timely treatment.