Kinetics of Visual Axis and Pupil Diameter during Caregiver-assisted Eating

: The purpose of this study was to examine the kinetics of the visual axis and pupil diameter during care-giver-assisted eating. The eating task was caregiver-assisted eating of twelve healthy volunteers. Visual axis position, spoon bowl motion, and pupil diameter were recorded using an eye tracker and a digital video camera. All participants indicated visual axis on a spoon or food during the motion of moving the spoon to the participant’s mouth in caregiv-er-assisted eating. Critical visual point (CVP) disappeared completely in all trials of all participants. The min-to-max and max-to-min pupil diameters, differences and changing were divided to three patterns for caregiver-assisted eating in all participants. Most patterns showed decrease of pupil diameter. These data suggest that the participant looked carefully at the food or the spoon using an accommodation reflex and a convergence reflex. Caregiver-assisted eating is natural in non CVP. A participant does not have somatosensory information during eating motion in caregiver-assisted eating. Positional information of a spoon is obtained only from visual information. We speculated that participant anxiety was stronger with caregiver-assisted eating than with unassisted eating. However, the causes of an increase and lack of change in pupil diameter remain unclear. Occupational therapists, who understands biological responses during eating motion, must teach a caregiver-assistant methods that are suitable for a participant.