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Matthew A. Timmis, Shahina Pardhan; The Effect of Central Visual Impairment on Manual Prehension When Tasked with Transporting-to-Place an Object Accurately to a New Location. Invest. Ophthalmol. Vis. Sci. 2012;53(6):2812-2822. doi: 10.1167/iovs.11-8860.
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To investigate whether differences exist between visually impaired and normal vision participants when completing a visually guided manual prehension task of transporting-to-place an object accurately to a new location.
Participants with central visual impairment (n = 17) and normal vision (n = 10) were tasked with reaching-to-grasp an object and then transporting-to-place it accurately to a different (predefined) location. Analysis assessed movements of the object transport phase and error in object placement. Correlation analysis assessed the association between the movements and mean loss in the central 5°, 10°, and 20° of participant's integrated binocular visual field (VF), visual acuity (VA), and contrast sensitivity (CS).
Compared to normal vision participants, visually impaired participants took significantly longer to complete the movement and exhibited increased deceleration time, greater number of velocity corrections, and more errors in object placement (P < 0.05). Findings demonstrated that participants with central visual impairment were more cautious when executing the movement, which contributed to uncertainty regarding end-position location. A higher number of movement indices were correlated with loss in the central 5° compared to the 10° and 20° of the VF. VA and CS were significantly correlated with a number of movement variables.
Despite the increased time taken by visually impaired participants to complete the task, they were still less accurate than normals when placing the object. Decrements in movement control were most associated with loss in the central 5° when compared to the central 10° and 20° of the VF, which was evidenced in the deceleration/“online” component of the movement.
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