How do flanking objects affect reaching and grasping behavior in participants with macular disorders?
OBJECTIVE
To investigate how objects (flankers) placed on either side of a target affect reaching and grasping behavior in visually impaired (VI) subjects due to macular disorders compared with age-matched normals.


METHODS
Subjects reached out to grasp a cylindrical target placed on its own and when it had two identical objects (flankers) placed either half or one target diameter away on each side of the target. A motion analysis system (Vicon 460) recorded and reconstructed the 3-dimemsional (3D) hand and finger movements. Kinematic data for transport and grasping mechanisms were measured.


RESULTS
In subjects with VI, crowding effected the overall movement duration, time after maximum velocity, and maximum grip aperture. Maximum effect was shown when the flankers were placed close to the target (high-level crowding) with a decreased effect shown for flankers placed farther away (medium-level crowding). Compared with normals, subjects with VI generally took longer to initiate the hand movement and to complete the movement. Time after maximum velocity and time after maximum grip aperture were also longer in subjects with VI. No interaction effects were found for any of the indices for the different levels of crowding in the two visual groups.


CONCLUSIONS
Reaching and grasping behavior is compromised in subjects with VI due to macular disorders compared with normals, and crowding affected performance for both normal subjects and those with VI. Flankers placed half an object diameter away showed greater deterioration than those placed further away.
Vision and Eye Research Unit, Postgraduate Medical Institute, Anglia Ruskin University, Cambridge, United Kingdom. shahina.pardhan@anglia.ac.uk
Shahina
S
Pardhan
Carmen
C
Gonzalez-Alvarez
Ahalya
A
Subramanian
Susana T L
ST
Chung
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008266:Macula Lutea / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance / Q000502:physiology*; D012164:Retinal Diseases / Q000503:physiopathology* / Q000523:psychology; D015354:Vision, Low / Q000503:physiopathology* / Q000523:psychology; D014796:Visual Perception / Q000502:physiology*