One of the main hindrances to testing these hypotheses further has been the invasive nature of LP, which involves inserting a large-bore needle into the spinal column. This procedure has a relatively high risk of complications given its proximity to the spinal cord and the potential for traumatic nervous system injury if improperly performed. In contrast to this invasive procedure, a non-invasive computational device was recently developed and CE mark approved to measure CSFp using a two-depth transcranial Doppler device (TDTCD). The underlying principle of the device involves the ophthalmic artery. When originating from the internal carotid artery, the ophthalmic artery is within the subarachnoid space and thus is mildly compressed by CSFp. After exiting the intracranial space into the orbit, the ophthalmic artery loses its subarachnoid surrounding, and is no longer affected by CSFp. The TDTCD applies minimal external pressure to the orbit such that the pressure exerted externally on the extracranial segment is equivalent to the CSFp exerted on the intracranial segment (as measured by Doppler signals of both vessels.) The safety of the device has been demonstrated and verified; it has obtained CE certification in Europe, and is currently awaiting FDA approval with a "Non-Significant Risk" categorization. Further details regarding the device can be viewed at www.vittamed.com.