Series Advances in Experimental Medicine and Biology, Volume 438, 1998 Plenum Press, 1027-1032
|CORRELATION BETWEEN PUPIL DIAMETER AND VISUALLY INDUCED DISCOMFORT|
|Tạp chí Series Advances in Experimental Medicine and Biology 2002 1998; 438 ():1027-1032|
|Tác giả||Vo Van Toi *, D. S. Landmann|
|Nơi thực hiện||Department of Biomedical Engineering, Bioengineering Center,Tufts University, 4 Colby Street, Medford, MA 02155|
|DOI URL [ PDF]|
Purpose: This investigation explores whether discomfort induced by visual stimulation causes a variation in pupil diameter. This can be used as an objective index of discomfort in virtual reality studies and clinical investigations.
Methods: Three male and three female observers, naïve to the study, average age 26±12.7 years old, participated in the study. Visual stimulation was induced by an optokinetic drum, which consists of alternating black and white stripes (14° arc) that rotated past the subject at 10 rpm. Illuminance was 150 lux and remained constant throughout the experiment. Observers wore a head-mounted eye-tracking device (I-SCAN) which measured pupil diameter at 60Hz. Before the experiments, subjectivity to motion sickness of the observers was evaluated using a standard questionnaire1. During the experiment, every 30 seconds, observers recorded their subjective level of discomfort (from 1 to 4) using a handheld microprocessor controlled data acquisition device that we developed. At the end of the experiment, overall observer's discomfort felt throughout the study was evaluated using a standard Simulator Sickness Questionnaire2 (SSQ). Two sets of experiments were administered. First, to establish a baseline pupil diameter, observer's pupil diameter was recorded for 8 min without visual stimulation. Second, the experiment to induce visual discomfort with the rotating drum was performed for a maximum of 25 min or until observers requested termination; during that time the pupil diameter and the subjective level of discomfort were measured.
Results: Two observers were placed in each of three tiers of discomfort based on the SSQ: “mild”, “moderate” or “severe”. Upon initiation of drum rotation, pupil dilation was noticed in all observers (p=0.008), and was most remarkable in the “severe” group. Pupil diameter dilated by an average of 18% in the “severe” group and only 7% in the “mild” group.
Conclusion: Changes in mean pupil diameter in response to vection is measurable and statistically significant. There is a strong correlation between the susceptibility scores, the percent increases in mean pupil diameter and the symptoms of discomfort. These results suggest that the pupil diameter can be used as an objective index to assess levels of visually induced discomfort.