With some ophthalmological instruments, the patient to be examined or treated needs to gaze in a defined direction. Accordingly, the operator needs the most objective possible information as to whether the patient actually fixates the fixating target or when this may no longer be the case. The invention makes it possible to monitor fixation economically with a short reaction time and with high accuracy. Monitoring of the fixation of an eye is accomplished in an economical manner with a short reaction time and high accuracy through spectroscopic detection of fixation, particularly by identifying a reflection at the fovea or foveola based on different reflectance factors compared to the rest of the retina.