Effect of visual impairment on goal-directed aiming movements in children.

This study investigated potential differences in motor control between children with a visual impairment (diagnosed albinism; n=11, mean age 8y 4mo [SD 7mo]; seven males, four females,) and children with normal vision (n=11, mean age 8y 4mo [SD 7mo]; six males, five females). Mean near visual acuity in the albinism group was 0.19 (SD 0.07, Snellen: 20/104). Children performed two types of movements (discrete and cyclic) in two orientations (azimuthal and radial, i.e. along the viewing and lateral direction), and with two amplitudes (10 and 20cm). All movements were performed in two subsequent target conditions: with and without visual information on the target location. Overall, children with visual impairment displayed larger endpoint variability. Discrete movements and movements over large distances were less fluent in both groups, but especially in the children with visual impairment. Children with visual impairment seemed to have more difficulties with calibrating the sensory information. Specifically, they made larger errors along the lateral direction, when the target was not visible. Results suggest that children with visual impairment have specific differences in motor control compared with children with normal vision, which are not all directly related to their poorer vision.