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Jennifer C. Brooks, D. Alfred Owens; Effects of luminance, blur, and tunnel vision on postural stability. Journal of Vision 2001;1(3):304. doi: 10.1167/1.3.304.
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As witnessed in large-screen theaters, optical flow in the visual field induces vivid sensations of self motion, an effect called vection. Leibowitz, Schupert-Rodemer, and Dichgans (1979) reported that the subjective magnitude of vection is unaffected by reductions of luminance and by refractive errors of up to 20 diopters. Leibowitz et al. subsequently called attention to the fact that focal vision is selectively degraded by low luminance and blur, while ambient functions appear not to be impaired. The present study extended this line of inquiry to investigate the effects of luminance, blur, and field reduction on postural stability, as measured by a posture platform. In Experiment I, subjects viewed a stationary field under three stances (unipedal, heal-to-toe, and bipedal), while vision was reduced from full-field to tunnel vision to eyes-closed. As expected, posture was increasingly destabilized as visual information was reduced. In Experiment II, a second group of subjects viewed a field in the frontal plane that rolled about the point of fixation. Three conditions were tested: normal, blurred [10 D], and tunnel vision [2 deg.], each at both high and low luminance [100 & 0.025 cd/m2]. Subjective ratings of vection and objective measures of body sway showed that, in addition to feelings of self-motion, the rolling field induced postural sway for all viewing conditions except tunnel vision. These findings are consistent with Leibowitz's selective degradation hypothesis, which asserts that ambient visual control of posture and locomotion is resilient to functional impairments under conditions that severely degrade focal vision.
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