Effects of Shock-Containing Whole-Body Vibration on Visual Acuity

Abstract

Using an experimental-system simulating the actual workplace of earth-moving machines, the effects of vertical (z-axis) whole-body vibration with various amplitudes and numbers of shocks, but a constant frequency-weighted acceleration of 1.25 m/s² rms, on visual acuity were examined. The visual acuity was estimated on the basis of the number of errors in discriminating the Landolt ring in front of the subjects under the vibration exposure. The magnitude of shocks (peak amplitude of 6–10 m/s²) and the number of shocks per unit time (shock cycle of 10–40 s) were varied, and two kinds of shocks (symmetric and asymmetric) were used. All shock-contained vibrations, including shockless vibrations with the same constant frequency-weighted acceleration, induced adverse effect on the visual acuity as compared with the test performed without vibration. No evident effect of shock below the amplitude of 10 m/s² on visual acuity was observed as compared with that at shockless vibration. But the symmetric and asymmetric shock-containing vibrations with the shock peak amplitude of 10 m/s² decreased the visual acuity. Especially, in the case of the vibration with symmetric shock, the instantaneous errors were observed immediately with the exposure of the shock of 10 m/s². These results demonstrated that shocks with peak amplitudes at or above 10 m/s² induced deteriorating effects on the visual acuity.