Visual Acuity under Vibration

Abstract

The influence of vertical sinusoidal vibration on the visual acuity of twelve human subjects, sitting restrained and without padding in an airplane seat mounted on a shake table, was investigated in the frequency range of 1 to 20 c/s. A. novel visual acuity tester was developed to achieve high accuracy of measurement and to obtain a great many observations in short time periods. The decrement of visual acuity normalized 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 had been determined by other methods. Below 12 c/s the decrements were due mainly to the physiological stress produced in the body and above 12 c/s to the image displacement on the retina which had more and more of a blurring effect. Measurements one minute after cessation of vibration indicated residual effects only at frequencies up to 12 c/s, peaks being at the same resonant frequencies.

Decrements in Tracking and Visual Performance during Vibration

“…Four studies (Lange and Coermann, 1962;Loeb, 1954;1955;Schmitz, et al, 1960) used visual acuity tasks; five studies (Dennis, 1965a;1965b;Mozell and White, 1958;Taub, 1964;Teare and Parks, 1963) used number-reading tasks. Because the A L L A N M .…”

“…This curve shape may be due to the eyeball or facial tissue resonance that Lange and Coermann (1962) and Dennis (1965a) discuss, although it is not clear why such resonance should affect visual performance any more than it would affect tracking performance. In other respects, the data plotted in Figures 1 and 3 visual acuity score of 1.15 in one of the Schmitz, e t al., conditions yielded a percentage decrement of 12%; these percentages then have a maximum value of 100% just as those in Figure 3.…”

“…In other respects, the data plotted in Figures 1 and 3 visual acuity score of 1.15 in one of the Schmitz, e t al., conditions yielded a percentage decrement of 12%; these percentages then have a maximum value of 100% just as those in Figure 3. In contrast to the scores shown for Loeb and Schmitz, et al, the scores for Lange and Coermann (1962) were computed much the same way as the percentage-increase-in-error scores were computed for tracking in Figures 1 and 2. For this reason the Lange and Coermann percentage decrements are not limited to 100% as are those for Loeb and Schmitz, et al, or those in Figure 3.…”

The Effect of Vibration on Performance With Electro-Optical Aids to Night Vision

“…Even at high illumination levels, where target resolution is vastly superior, little loss of unaided acuity has been reported at these amplitudes. 3 The higher powered instruments, on the other hand, will certainly suffer more decrement, probably at an increasing rate as amplitude is increased. The unfortunate conclusion is that a great deal of the advantage inherent in the use of electro-optical aids may be lost under severe conditions.…”

“…literature relevant to the question of the effect of vibration on acuity. Indeed, the problem has been investigated many times over the years, 3 but the number of crucial variables involved has precluded systematic study of each. For acuity, for example, the factors of illumination level, degree of contrast, retinal position, and type of target, must be considered as well as frequency and amplitude of vibration and the position of the subject.…”