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Variables Affecting Dynamic Visual Acuity in Normal Adults

18 October 2013



Vision is one part of the balance system. The brain has to process, compile and make sense of self movement as well as movement in the environment using visual, vestibular and somatosensory information. Previous research has shown visual information reduction causes performance measures to decline in many physical tasks. Monocular blur is quite common, having several causes, some even voluntary. It is important to know if monocular blur causes any decreases in accurately interpreting the moving world, potentially impacting balance and safety. This research’s aim was to investigate whether a decrease in visual information with monocular blur is measurable as a change in dynamic visual acuity (DVA), even in relatively young and healthy populations; and whether this altered visual information also causes postural instability (i.e. increases sway). Participants were tested using the inVision™ system by NeuroCom, Intl. (, while standing on a force platform, BASIC Balance Master®, made by the same company. The inVision™ system accurately measures DVA in logMAR and the Balance Master measures postural sway in deg/sec. All DVA measurements-static visual acuities, target following acuities, and head shaking acuities- were taken with or without monocular blurring spectacles. Simultaneously, sway readings were taken during each of the DVA conditions. It was expected that static binocular acuities would have little change with monocular blur, and there would be decreased acuities in both target following and head shaking measures. However, the static acuities were the most significantly different with blur than without (p=0.000), followed by the moving target acuities (p=0.001), but not head moving acuities. Sway measures were expected to increase with blur in all three conditions, especially during the increasingly challenging, target following and head shaking, dynamic viewing conditions. Yet, the sway measures did not significantly increase in all conditions. Only with the head moving condition was there a statistically significant increase (p=0.021). While the significant results were not as expected in all conditions of both categories of vision and sway, there was a measurable decrease in some performances in each category of this younger healthier population. As age increases, so do the risks of monocular blur and balance deficits. Further studies with older populations and those at greater risks for falls need to be done to better understand the risks associated with monocular blur.


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