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

Abstract

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.

Gaze–grasp coordination in obstacle avoidance: differences between binocular and monocular viewing

“…Moreover, adults with binocular dysfunctions due to these conditions exhibit similar deficits when reaching to grasp isolated objects (e.g., Grant et al 2007;Melmoth et al 2009;Pardhan et al 2011) to those of normal subjects forced to perform equivalent actions using one eye alone. This raises final questions as to whether sub-optimal gaze strategies are adopted when binocular vision is reduced or absent and whether this contributes to poorer hand action control.…”

The Effect of Central Visual Impairment on Manual Prehension When Tasked with Transporting-to-Place an Object Accurately to a New Location

“…Additional information pertaining to the capture system can be found elsewhere. 9 Retro-reflective spherical markers were attached at the following key anatomical locations (placed either directly on the skin or clothing): distal border of the thumbnail and index fingernail, styloid process on the radial side of the wrist, sternum, and the anteriolateral and posteriolateral aspects of the head. An additional marker was attached at the top of each object at the center.…”

“…While research that simulates visual impairment in young normal vision adults provides some important insights into the functional limitations associated with visual impairment, [4][5][6][7] these findings are limited when drawing inferences about the visually impaired population as it does not account for long-term visuomotor adaptation to vision loss 9 or the effects of age on manual prehension. 17 Research investigating the effects of actual visual impairment on daily function has highlighted that when patients with peripheral or central visual impairment complete a reach-and-grasp task, they exhibit delayed onset and longer movement times, [8][9][10][11] lower peak velocities, and impaired grip scaling (central visual impairment only [9][10][11] ) compared to age-matched adults with normal vision. These aforementioned studies all measured participants' ability to reach-and-grasp an object, whereas, in daily life, we are required to perform a variety of other manual prehension tasks such as grasping objects and then transporting-to-place them accurately to a different location; how this affects individuals with central visual impairment has not been previously investigated.…”

“…Moreover, this study examines parameters that have not been examined before in studies on reaching and grasping in visual impairment. [9][10][11] Since participants were required to locate and pick up the object and then to also locate the end position through visual search, there is arguably a greater visual demand placed on the participant compared to the previous reach and grasp tasks. This reflects a more realistic task found in the home/kitchen.…”

“…Indeed, decrements in reach-and-grasp performance have previously been highlighted through simulating both peripheral [4][5][6][7] and central 6 visual impairment in young normal vision adults, and in actual visual impairment in older adults with peripheral and central impairment from eye diseases such as glaucoma 8 and agerelated macular degeneration. [9][10][11] Since we live in an aging population [12][13][14] and visual impairment is linked with increased age, 15,16 it is important that we continue, through ongoing investigation, to increase our understanding of the effects that visual impairment has on daily function. A greater understanding will facilitate the development of increasingly effective rehabilitation techniques.…”