How does the presence and duration of central visual impairment affect reaching and grasping movements?

To examine how subjects with central visual impairment (CVI) due to macular degeneration conduct reaching and grasping movements compared to those with normal vision and to determine whether these are influenced by the duration of the impairment.

Eighteen subjects with CVI and 9 subjects of a similar age but with normal vision were recruited. Subjects were required to pick up a cylindrical object and a motion analysis system recorded and reconstructed the reaching and grasping movements in 3-D. Subjects were also divided into two groups based on the duration of their vision loss: subjects with CVI of less/greater than 10 years duration.

Subjects with CVI showed significant differences in some transport and grasping indices compared to age matched normal subjects (p < 0.05) but not in all. More indices were correlated to contrast sensitivity (5) than to visual acuity results (2).

Subjects with CVI required extra time prior to starting the movement (as shown by longer onset time) and this was probably needed to localise the object and to perceive its dimensions. They spent more time after maximum grip aperture, indicating a need for a longer time to grasp the object. A possible reason is that visually impaired patients need to use more tactile information than normal subjects in order to fully execute grasping of the object. CVI that was of <10 years in duration affected more indices compared to CVI that was of long standing and may suggest adaptation to the visual impairment for this task.