The effects of acceleration forces on night vision

The effects of Gy and Gz acceleration forces on cone-type mesopic vision threshold values are examined. An experiment has been conducted on the Dynamic Environment Simulator, a three-axis human centrifuge, to reproduce an acceleration environment in a simulated night-flight combat situation. Acceleration environments studied were levels of +1 Gz, + 1Gy, +1.4 Gz, +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz. A visual task was performed which determined 20/50 visual acuity illumination threshold values. Physiological parameters recorded were arterial oxygen saturation (SaO2) by ear oximetry, heart rate, and visual acuity threshold values. There were 10 male subjects, all members of the United States Air Force. Their ages ranged from 25-39 years (mean +/- S.D., 29.1 +/- 4.3). Results were zero means obtained by self-pairing with +1 Gz controls. Analysis was done by self-pairing, two-tailed t test. Results showed no significant shift in luminance threshold values at +1 Gy or +1.4 Gz, and significant increases in luminance thresholds at the 0.01 level for +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz.