Patient interface for coupling an ophthalmological application head for applying optical radiation of a radiation source onto an eye of a patient, the patient interface comprising: a patient-side interface structure, which is designed for coupling to the eye of a patient; a source-side interface structure, which is designed to couple the patient interface rigidly to the application head or to an intermediate element provided to be arranged between application head and patient interface, wherein the source-side interface structure comprises a first source-side patient interface coupler and an additional second source-side patient interface coupler, characterized in that: the first source-side patient interface coupler is designed such that, proceeding from an uncoupled starting state in which the patient interface is not coupled to the application head or the optionally present intermediate element and is thus separate therefrom, it limits the mobility of the patient interface with respect to the application head or the intermediate element by producing a coupling to a first patient interface coupler counterpiece of the application head or of the intermediate element, and the second source-side patient interface coupler is designed such that, by producing a coupling to a second patient interface coupler counterpiece of the application head or of the intermediate element, it couples the patient interface rigidly to the application head or the intermediate element while the first source-side patient interface coupler is already coupled to the first patient interface coupler counterpiece. a patient-side interface structure, which is designed for coupling to the eye of a patient; a source-side interface structure, which is designed to couple the patient interface rigidly to the application head or to an intermediate element provided to be arranged between application head and patient interface, wherein the source-side interface structure comprises a first source-side patient interface coupler and an additional second source-side patient interface coupler, characterized in that: the first source-side patient interface coupler is designed such that, proceeding from an uncoupled starting state in which the patient interface is not coupled to the application head or the optionally present intermediate element and is thus separate therefrom, it limits the mobility of the patient interface with respect to the application head or the intermediate element by producing a coupling to a first patient interface coupler counterpiece of the application head or of the intermediate element, and the second source-side patient interface coupler is designed such that, by producing a coupling to a second patient interface coupler counterpiece of the application head or of the intermediate element, it couples the patient interface rigidly to the application head or the intermediate element while the first source-side patient interface coupler is already coupled to the first patient interface coupler counterpiece. the first source-side patient interface coupler is designed such that, proceeding from an uncoupled starting state in which the patient interface is not coupled to the application head or the optionally present intermediate element and is thus separate therefrom, it limits the mobility of the patient interface with respect to the application head or the intermediate element by producing a coupling to a first patient interface coupler counterpiece of the application head or of the intermediate element, and the second source-side patient interface coupler is designed such that, by producing a coupling to a second patient interface coupler counterpiece of the application head or of the intermediate element, it couples the patient interface rigidly to the application head or the intermediate element while the first source-side patient interface coupler is already coupled to the first patient interface coupler counterpiece.