Acceleration Effects on Pupil Size with Control of Mental and Environmental Factors


  1. Cheung, B.
  2. Hofer, K.
Corporate Authors
Defence R&D Canada - Toronto, Toronto ONT (CAN)
Background: Using still photography and cinematography, early studies reported that pupils dilate immediately upon exposure to acceleration and the dilation persists during sustained +Gz. Due to the lack of control for mental and environmental factors and poor sampling rate in early techniques, we re-examined the effects of increased acceleration on pupil size in the human centrifuge. Methods: Eight volunteers were dark adapted for 20 minutes by fixating on a 2.5 mm LED disc, 1 m away in otherwise complete darkness. Pupil diameters, horizontal and vertical eye movements were recorded binocularly in real time using an eye-tracking and pupillometry system. The recording sequence consists of one minute at +1Gz, followed by transition to +3Gz at 0.1G/s, 2 minutes at sustained +3Gz, returned to +1Gz at 1G/s, and finally maintained at +1Gz for another minute. During this sequence, the subject's heart rate was also monitored and the subject was instructed to subtract 2 from 1000 to maintain mental alertness. Results: All subjects showed a significant decrease in pupil diameter (p < 0.05) and increase in heart rate (p = 0.02) during +3Gz and regained the baseline level upon returning to +1Gz. The maximum decrease in pupil diameter during sustained acceleration ranged from 0.6 to 3.3 mm. Conclusion: Our findings are consistent with the observation that pupils dilate during hypogravity and constrict during hypergravity phase of parabolic flight. It appears that the reflex regulation

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Pupil size
Report Number
DRDC-TORONTO-SL-2002-149 — Scientific Literature
Date of publication
01 Jun 2003
Number of Pages
Reprinted from
Aviation, Space, and Environmental Medicine, Vol 74, no 6, 2003, p 669-674
Electronic Document(PDF);CD ROM

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