This seems to be something very specific in relation to psychiatry and is not simply normal looking around.

"Facial-affect recognition and visual scanning behaviour in the course of schizophrenia ...
The performance of schizophrenic in-patients in facial expression identification was assessed in an acute phase and in a partly remitted phase of the illness. During visual exploration of the face stimuli, the patient's eye movements were recorded using an infrared-corneal-reflection technique. Compared to healthy controls, patients demonstrated a significant deficit in facial-affect recognition. In addition, schizophrenics differed from controls in several eye movement parameters such as length of mean scan path and mean duration of fixation. Both the facial-affect recognition deficit and the eye movement abnormalities remained stable over time. However, performance in facial-affect recognition and eye movement abnormalities were not correlated."
http://www.ncbi.nlm.nih.gov/pubmed/9134591


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Note added at 1 hr (2011-05-08 12:43:41 GMT)
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Looking at this reference, it is clear that scanning per se is not abnormal, however the type of scanning used by a subject is used diagnostically.

"The scanning behaviour of people can differ strikingly due to cognitive structure (Klein 1954, for
the references see Davidoff p.72), cross-cultural differences (Hudson 1967, for the references see
Davidoff p.91), attentional difference, and psychiatric disorders (Gaebel et al. 1987).
Gardner et al. (1959) considered that each individual has a basic cognitive style which can affect
the way in which visual input is processed. Individuals have different degrees of scanning control
and differ in the extensiveness of the search and field articulation. Field articulation relates to
selective attention over the visual field. Klein (1954) has anticipated that people with a
constricted cognitive style tend to scan narrowly, whereas flexible people would scan over a wide
area. He has suggested that under stress wide scanners increase their scanning behaviour, while
narrow scanners tend to decrease (for the references see Davidoff p.84)."
http://www.humlab.lu.se/resources/publications/studentpapers...

I'd say that in the context, this would involve constantly scanning the room with the eyes moving all the time, left to right, up and down, in a state of high alert.