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The aim of this study was to investigate where neurologists look when they view brain computed tomography (CT) images and to evaluate how they deploy their visual attention by comparing their gaze distribution with saliency maps. Brain CT images showing cerebrovascular accidents were presented to 12 neurologists and 12 control subjects. The subjects' ocular fixation positions were recorded using an eye-tracking device (Eyelink 1000). Heat maps were created based on the eye-fixation patterns of each group and compared between the two groups. The heat maps revealed that the areas on which control subjects frequently fixated often coincided with areas identified as outstanding in saliency maps, while the areas on which neurologists frequently fixated often did not. Dwell time in regions of interest (ROI) was likewise compared between the two groups, revealing that, although dwell time on large lesions was not different between the two groups, dwell time in clinically important areas with low salience was longer in neurologists than in controls. Therefore it appears that neurologists intentionally scan clinically important areas when reading brain CT images showing cerebrovascular accidents. Both neurologists and control subjects used the “bottom-up salience” form of visual attention, although the neurologists more effectively used the “top-down instruction” form.

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The problems associated with watching stereoscopic HDTV have been classified into three groups, one of which is how natural/unnatural stereoscopic pictures look to viewers. It is known that the shooting and viewing conditions affect the depth ofa stereoscopic image, and this depth distortion is a major factor influencing the viewer's stereoscopic perception. The second group concerns the visual comfortldiscomfort. Visual discomfort is caused by the difficulty of fusing left and right images because of excessive binocular parallax and its temporal changes. We have studied how visual comfort is affected by the range of parallax distribution and temporal parallax changes. The results show that stereoscopic images are comfortable to view for an angular parallax of up to about 60 minutes and that visual comfort is achieved if discontinuous temporal changes are angle of 60 minutes or less. The third group concerns visual fatigue that a viewer experiences after viewing a stereoscopic HDTV program, which is thought to be mainly caused by the mismatch between the eyes' convergence and accommodation. We confirmed that, after observing stereoscopic images for about an hour, the fusion range diminishes and the viewer's visual functions deteriorate as a result.