Visual Acuity under Vibration

The injuence of vertical sinusoidal vibration on the visual acuity of twelve buman su&ects, sit ting restrained and without padding in an airplane scat mounted on a shake table, was investigated in the frequency range of 1 to 20 CIS. A novel visual acuity tester was developed to achieve hkh accuracy of measurement and to obtain a great many observations in short time periods, The decrement of visual acuity norma fixed to a shake table acceleration of one g (vector) was determined. Maximum decrements occurred at those frequencies where resonances of the whole body and organ complexes bad been determined by other methods. Below 12 CIS the decrements were due mainfy to t~ephyJiologicalstrcssproduced in the body andabove 12 CIS to the image displacement on the retina which bad more and more of a blurring effect. Measurements one minute after cessation of vibration indicated residual effects only at frequencies up to 12 CIS, peaks being at the same resonant frequencies