Eye Motion during Whole-Body Vertical Vibration

Abstract

An experiment was conducted to determine whether the minimum levels of whole-body vertical (a_z) vibration likely to produce decrements in visual acuity cause angular or linear eye motions. If vibration causes predominantly angular eye motion, the movement of the retinal image of an object will be independent of the distance between the eye of the vibrating person and the stationary object being viewed. If the eye motion is linear, the image motion will be inversely proportional to the viewing distance. For six seated subjects the minimum levels of vibration required to produce a perceptible blur of stationary point sources of light were determined for viewing distances of 1.2 and 6.0 meters at vibration frequencies of 7, 15, 30, and 60 Hz. It was found that the levels of vertical (a_z) vibration on the seat and vertical and pitch vibration at the head were independent of viewing distance. It was concluded that the minimum levels of vertical vibration required to produce blur cause angular motion of the eye. In some vibration environments a reduction in viewing distance will, therefore, often improve vision since it will increase the size of the retinal image of an object without significantly increasing the retinal image displacement due to whole-body vibration.