The invention proposes a manual measuring appliance (112) and an analytical measuring system (110) which can be used to measure at least one analyte in an eye fluid of an eye (114). The handheld measuring appliance (112) comprises a measuring system (120) and a positioning system (122). The measuring system (120) can measure at least one property of the at least one analyte and/or at least one analyte-dependent change of property of at least one ocular sensor (116) in the eye fluid, and this can be used to infer a concentration of the analyte in the eye fluid. The positioning system (122) is set up to measure a spatial positioning, wherein the spatial positioning comprises a distance between at least one measurement location in the eye (114) and the handheld measuring appliance (112) and also furthermore at least one further positioning co-ordinate. Furthermore, the handheld measuring appliance comprises a calibration system (128), wherein the calibration system (128) is set up to perform a comparison measurement of at least one analyte concentration in a body fluid and/or to adopt measurement data from a comparison measurement performed using a separate measuring appliance and to take them into account when determining the concentration of the at least one analyte.