Perceptual and oculomotor implications of interpupillary distance settings on a head-mounted virtual display

Little effort has been put into determining the role of interpupillary distance (IPD) in operator perception of a virtual environment (VE). The present study examined perceptual and oculomotor variables across four IPD settings in a binocular head-mounted display (HMD). The subjects wore a HMD for 15 minutes while manually estimating the size of two-dimensional objects in a VE. A within-subjects design exposed each subject to four different experimental conditions: (1) the subject's anatomical IPD, (2) 5.0 cm (the minimum setting on the HMD), (3) 6.3 cm (adult mean), and (4) 7.4 cm (the maximum setting on the HMD). Task-induced adaptation of far acuity, accommodation, and vergence were measured. After the task, each subject completed a survey that indexed the severity of any HMD-induced fatigue. Size judgments were not affected by IPD condition. Further, IPD settings did not influence adaptation of dark vergence, of dark focus, or of far binocular acuity. However, in the 5.0 cm and 7.4 cm IPD conditions, subjects reported significantly more fatigue than in the anatomical and 6.3 cm conditions. These findings suggest that IPD settings do not influence size perception of a two-dimensional virtual object, but are related to operator comfort. The implications are examined in reference to training procedures and entertainment uses of virtual environments.