Elevated intracranial pressure is a common complication of brain injury which means that the pressure within the skull rises above normal levels. The negative impact of increased intracranial pressure (ICP) on the prognosis of patients has been strongly shown in numerous studies and ICP-based treatment is associated with an important reduction of risk of death. Invasive ICP measurement methods are nowadays a standard of care in severe brain injury. The two available ways of measuring ICP require neurosurgical procedure to implant a catheter and probes within the brain and present risks and complications for the patient, such as infections and intracranial bleeding. In addition, invasive recording of ICP requires neurosurgical expertise and intensive care unit (ICU) facilities, limiting the application of ICP measurements to patients of the acute neuro-ICU (neuro-Intensive Care Unit) with acute brain damage requiring close surveillance to prevent further deterioration of neural tissue and disability. Non-invasive ICP monitoring benefits include no risk of complications seen in invasive monitoring, helping in deciding which patient needs invasive ICP monitoring, and providing ongoing long-term measurements of ICP without having to insert a new device every time. Although many non-invasive ICP measurement methods have been explored, to date, none of them have shown clinical success or usefulness. One under-explored window to ICP is the orbital vein, a small blood vessel located near your eye, which we think could provide a direct link to the intracranial pressure. The study device, called the CPMX3 system, is a non-invasive method to measure pressure in a superficial periorbital vein.