the sensor 40 may record parameters of the treated tissue 30 the evaluation unit 50 may output control signals and or warning signals the operating device 10 may include additional components during a medical intervention a medical instrument 20 may be used to treat the tissue 30 of a patient an operation may be carried out to remove diseased tissue 34 the diseased tissue 34 may be for example cancerous tissue that is completely removed with as little healthy tissue 32 as possible being removed vulnerable tissues e g nerve tracts blood vessels bile ducts should not be damaged as shown in fig1 the medical instrument 20 may include a laser device 22 that removes diseased tissue 34 the sensor 40 is assigned to the laser device 22 the sensor 40 may be for example an optical sensor in which a transmitter 42 emits light at a certain wavelength onto the tissue 30 to be treated a receiver 44 records the illuminated area and the light reflected from the illuminated area a distinction between nerve tissue other tissue and malignant cancerous tissuemay be made on the basis of different optical properties of these tissue types fluorescent markers may be used the flourescent markers may only adhere to and unambiguously mark cancerous cells the values measured by the sensor 40 are sent to the evaluation unit 50 the evaluation unit 50 evaluates the values by an integrated signal processing unit for example the values measured by the receiver 44 are compared with known data about tissue structures the tissue of the area to be treated is classified according to the comparison electronic sensors may be used electronic sensors may measure the conductivity of the tissue to be treated and to classify the tissue.