Patricia Cisarik, Gabriel Fickett; Perception of Illusory Motion in the Rotating Snake by the Aged: Pupil Size and Retinal Illumination. Journal of Vision 2014;14(10):268. doi: 10.1167/14.10.268.
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© ARVO (1962-2015); The Authors (2016-present)
Decline of visual functions occurs with aging.1 Perceived motion in repeated asymmetric stationary patterns, such as Kitaoka's Rotating Snakes, is no exception: Billino, et al. reported that only 23.7% of their 38 subjects 65+ years of age perceived the illusory motion, compared to 100% perception by young adults.2 Neurophysiology data provides evidence that timing differences in V1 cell responses to luminance contrast variations account for the illusion;3 therefore, degeneration of visual cortex with age4 has been suggested to cause degraded perception of this illusory motion.2 Since senescent optics of the eye insufficiently explain the decline of several visual functions,6,7 the contribution of pre-cortical factors to the age-related decline in illusory motion perception is presumed to be minimal and has not been investigated. Because reduced retinal illumination degrades the perception in young subjects,5 we initiated a pilot study in individuals aged 60+ years to qualitatively investigate the effects of retinal illumination on illusory motion perception in the elderly. Inconsistent with Billino, et al., 80% of our subjects perceived motion in the Rotating Snakes, possibly due to the younger mean age of our group (69.6 vs. 73 years). A t-test for independent samples indicates that the mean age of those who perceived the illusion is younger (67.8 vs. 76.2 years, p = .01) and the mean pupil size is larger (3.8mm vs. 2.4mm, p = .002) than the mean age and pupil size of those who did not perceive the illusion. In the subset of pseudophakic subjects, no difference was found in the mean age of those who did compared to those who did not perceive the illusion (p = 0.2); however, those who perceived the illusion had a larger pupil than those who did not (4.7mm vs. 2.3mm, p = 0.03). Our results suggest that reduced retinal illumination contributes to the declined perception of illusory motion in repeated asymmetric stationary patterns with aging.