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Amblyopes have difficulty judging object distance but not size when reaching and grasping in habitual viewing
Author(s) -
BARRETT BT,
PANESAR GK,
PACEY I,
BUCKLEY J
Publication year - 2010
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2010.448.x
Subject(s) - object (grammar) , computer vision , grasp , movement (music) , communication , artificial intelligence , mathematics , psychology , computer science , physics , acoustics , programming language
Purpose Prehension deficits exist in amblyopes when reaching for a single/isolated object in binocular viewing. Here, we examine prehension for objects that are flanked by nearby distracters. Methods Twenty amblyopes (36.4±11.7 yrs) & twenty visual normals (27.5±6.3 yrs) reached for a solid cylindrical object (height 12cm, diameter 3 or 4cm) located directly in front of the participant. The object was flanked by two similarly‐sized distracters placed either side of the object, or in front and behind it. The spacing between the object and distracters was scaled according to finger‐width of individual participants and was set at spacings of 2‐ and 4‐ finger‐widths. Shutter‐goggles prevented a view of spatial configuration until the movement was to be initiated. Opening the shutters provided the cue for participants to pick up the object in a singe, smooth movement. Movements of the arm, hand and object were recorded using an 8‐camera, Vicon‐IR recording system. Results Amblyopia affects both the ‘reach’ and the ‘grasp’ phases of prehension. Maximum grip aperture is the same in both groups suggesting that amblyopes are no worse at scaling their grip size to the size of object. But amblyopes show more cautious prehension behaviour. This is because maximum grip aperture and maximum reach velocity occur earlier in their reach, and because there is a longer time from the end of the reach to initial contact with object, and a longer time from contact to lift. Conclusion Our results suggest that amblyopes have more difficulty judging object distance than object size. However, the functional significance of these amblyopic versus visual‐normal differences in prehension outside the laboratory is as yet unclear.