There is described a probe device for optically investigating a tissue of a subject, comprising: a first probe element, a second probe element, and a third probe element each to be positioned at a respective vertex of a triangle for sensing the tissue, the first probe element each comprising a first light source for emitting light having a first wavelength, the second probe element each comprising a second light source for emitting light having a second wavelength and a first photodetector for detecting light having the first wavelength and scattered by the tissue, and the third probe element comprising a second photodetector for detecting light having the first and second wavelengths and scattered by the tissue.
