Pupillary response among VDU users in daylighted workplaces.

Daylighted workplaces can complicate the viewing of visual display unit (VDU) tasks. Incoming direct- and/or reflected-daylight components can distort surface luminance distributions in both the direct- and screen-reflected visual fields. Pupillary response to these sources moreover may differ significantly, for example, between window- and interior-exposures, affecting bilateral depth of field and accommodation. Accordingly, it is hypothesized that pupil diameter is a valid ergonomic indicator of visual comfort for viewing targets at workplaces with varying daylighting exposures. This hypothesis is tested by measuring the pupillary response of four VDU users, each while viewing three targets at each of six different workplaces in a daylighted room. An iriscorder is used to record pupil diameter independently for left and right eyes in response to keyboard, screen, and background-surround surface luminances. The significant differences in pupil diameter among the three targets at the six positions can be explained by the luminance differences rendered by the incoming daylight. On this basis, it is further hypothesized that smaller pupil diameters in response to a limited range of graduated luminances correspond to more comfortable viewing conditions. Provision of these viewing conditions hold implications for VDU workplace layout, work organization, and control of electric lighting and cooling loads.