How display polarity and lighting conditions affect the pupil size of VDT operators

This study ascertained that CRTs using a positive display polarity (dark characters on bright background) are ergonomically more appropriate for VDT operators than ones using a negative display polarity (bright characters on dark background), using both physiological and psychological indices. Differences of pupil size and subjective evaluation of visual comfort while undertaking visual tasks were examined for six experimental conditions (two CRT display types in three different illuminated levels). Pupil diameter was not affected greatly when working with the positive display for different illumination levels. The positive display also caused smaller differences in pupil diameter when viewing visual targets, namely CRT display, script, and keyboard, for all lighting conditions. The majority of the subjects also appreciated working with the positive CRT display at a regular office illumination level.