A method and apparatus for obtaining the absolute value of intracranial pressure in a non-invasive manner is described by using an ultrasonic Doppler measuring device which detects the intracranial and extracranial blood flow velocities of the intracranial and extracranial segments of the ophthalmic artery. The eye in which the blood flow is monitored is subjected to an external pressure, sufficient to equalize the intracranial and extracranial angle-independent blood flow factors calculated from the intracranial velocity signal and extracranial velocity signal. The absolute value of the intracranial pressure is identified as that external pressure at which such equalization occur
