The invention relates to a device for diagnosis and/or therapy of a selected portion of a body by optical reflectance or optical transmission. The device according to the invention has a laminar body (12) containing a tissue-facing surface (13). The laminar body (12) integrally forms a transmitter opening destined to accommodate a transmitter fiber terminal (24) and a receiver opening destined to accommodate a receiver fiber terminal (38a, 38b). Furthermore, it contains annular light shielding means for shielding said transmitter fiber terminal (24) and receiver fiber terminal (38a, 38b) from ambient light sources. Thereby, said annular transmitter and receiver light shielding means are formed as an annular transmitter light shielding bulge (46) and an annular receiver light shielding bulge (48a, 48b), respectively, which are firmly arranged with respect to said laminar body (12), whereby their free ends are protruding with respect to said tissue-facing surface (13) of said laminar body (12).