Device and method for determining retinal blood pressure values and for mapping retinal blood pressure values and perfusion pressure values

A method for determining retinal blood pressure values in a patient's eye (A), the method comprising:

• applying a variable stimulation pressure (SD) to the eye (A), causing changing of an intraocular pressure in the eye (A) as a function of the applied variable stimulation pressure (SD);
• observing the retina of the eye and/or recording a video sequence of images of the retina of the eye simultaneously with the applying the variable stimulation pressure (SD) to the eye (A);
• measuring a current intraocular pressure value by automatically using a tonometer;
• equating the current intraocular pressure value to one of the retinal blood pressure values if compliance with a characteristic measurement criterion for said one retinal blood pressure value is observed on the retina or derived from the images;
• keeping constant the variable stimulation pressure (SD) over a period of time when the compliance with the characteristic measurement criterion in at least one point in time is observed;
• performing a direct measurement of the intraocular pressure during said period of time of keeping constant the variable stimulation pressure (SD) by automatically using the tonometer;
• directly equating the direct measurement of the intraocular pressure to that one of the retinal blood pressure values for which said characteristic measurement criterion was met;
• obtaining a local retinal perfusion pressure value from the one of the retinal blood pressure values when the one of the retinal blood pressure values is a local retinal arterial blood pressure value, wherein the local retinal perfusion pressure value is obtained by calculating a difference between the local retinal arterial blood pressure value and a resting intraocular pressure value or a retinal venous blood pressure value outside the eyeball;
• representing the local perfusion pressure value in a pressure mapping image
• deriving illumination-independent spectrally normalized signals from the images of the video sequence and assigning the illumination-independent spectrally normalized signals to a point in time and a measurement location;
• and
• assigning a rise and fall of vascular pulsations, pulsatory and continuous pallor, or signal changes as further characteristic measurement criteria and/or assigning the global and/or local retinal blood pressure values as threshold values to the illumination-independent spectrally normalized signals;
• and
• using the further characteristic measurement criteria and/or the threshold values to automatically measure or determine the intraocular pressure.