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S. Pardhan, C. Gonzalez-Alvarez, A. Subramanian; How Does Visual Impairment Affect Reaching and Grasping Movements When the Visibility of the Target Object is Changed?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3621. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To examine how participants with visual impairment carry out hand motor movements such as reaching and grasping when the visibility of the object to be grasped is altered with respect to its background.
Kinematic indices for reaching and grasping were measured in eighteen participants with central field loss caused by age-related macular degeneration and compared to age matched normal subjects. All participants were required to pick up a cylindrical object under binocular viewing conditions using their best corrected spectacles. Two object sizes, two object distances and three target colours were used: black cup, white cup and a transparent cup. A motion analysis system (Vicon 460) recorded and reconstructed the 3D hand and finger movements. Transport component of the movement was measured using indices including maximum wrist velocity, time to maximum velocity, deceleration and total movement time. Grasp component was assessed using maximum grip aperture, time spent at and time after maximum grip aperture.
The total movement time, the onset time and time spent at maximum grip aperture were significantly higher in participants with visual impairment compared to normals (p<0.05). No significant differences were shown with other kinematic indices such as maximum velocity and deceleration time. Data are modelled in terms of visual acuity and contrast sensitivity scores. As expected, performance was worse when the visibility of the cup to be grasped was low compared to the background. Significant differences were shown for movement duration, time at maximum velocity, deceleration time and time at maximum grip aperture.
Although visual acuity and contrast sensitivity were significantly worse in participants with visual impairment, as long as the object to be grasped was clearly visible, some kinematic indices were as effective as in normal participants whilst others were significantly worse. Some parameters that were significant correlated with contrast sensitivity scores.
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