Abstract: The apparatus comprises a chamber (1) enclosed on all sides except for an opening (3) on one side to permit hermetical contact with the orbital borders. The chamber is equipped with a device (4) for increasing the pressure within the chamber, coupled to a manometer (6) and has a doppler probe (5) that may be connected to a doppler flowmeter. Applying an increasing positive pressure in the chamber, and thus upon the contents of the orbit, the doppler probe detects the moment of disappearance and reappearance of the blood flow signal, respectively. The point at which the signal ceases or first reappears corresponds to the systolic blood pressure in the ophthalmic artery.