Teaching is a complex and demanding endeavour. Teachers must deal with numerous forces, often face dilemma-ridden and ambiguous situations and have to act under time pressure. In order to accomplish these tasks, teachers must apply professional knowledge differentially (Fairbanks et al. 2009). In recent decades, various studies have focused on defining and investigating the domains of teachers' professional knowledge. In this respect, much attention has been paid of late to the concept of professional vision. In the present study, we look for indications of professional vision using eye tracking data and post hoc think-aloud verbalisations. We worked with student teachers and teacher educators, who watched a short video clip of a school lesson and described afterwards what they had seen. The video shows an authentic teaching situation and discloses a 'critical incident'. The results show that there are differences between the two groups of participants, both in terms of eye tracking and post hoc think-aloud verbalisation. However, the differences originate primarily from six teacher educators explicitly mentioning the 'critical incident' in the post hoc think-aloud verbalisation. As with other studies, these results indicate differences in professional vision between novice and experienced teaching professionals. Additionally, our analysis reveals that eye tracking data can assist in identifying professional vision.