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Aachal Kotecha, Rachel Fahy, Gary Rubin; The effects of central and peripheral visual losses on reaching and grasping. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2186.
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© ARVO (1962-2015); The Authors (2016-present)
This study aims to evaluate the relative contributions of central and peripheral vision to prehension in visually impaired adults.
Reaching and grasping was quantified using motion detection cameras (ProReflex, Qualisys AB, Sweden). Subjects reached and grasped one of two cylindrical objects placed at 20cm or 40cm from the hand. Measures were repeated 8 times under each test condition and the median used in subsequent analysis. Indices of prehension planning [movement onset (MO ms); peak speed (V mm/s), time to peak speed (ttV ms)], execution [movement duration (MD ms); path deviation ratio (PD)] grasping [peak grip aperture (PGA, angle), grip application time (GAT, ms)] and control [deceleration time (DT ms)] were quantified. Analyses were performed using repeated measures ANOVA.
The results of 9 control (C), 11 age related macular degeneration (AMD) and 12 glaucoma (G) patients during binocular viewing are presented. There were significant group differences in movement planning [MO: p < 0.01, V: p = 0.03, ttV: p < 0.01] and grasping [GAT:p < 0.01] with aspects of execution and online control approaching significance [MD: p = 0.06; PD, p = 0.1]. AMD and G patients had longer MO ('far,large' condition mean [standard error]: C = 274  ms; G = 378  ms; AMD = 439  ms), ttV (C = 594  ms; G = 719  ms; AMD = 766  ms) and GAT (C = 411  ms; G = 544  ms; AMD = 644  ms); however AMD reaching speed V was slower, suggesting a deficiency in some aspects of movement planning (C = 1032  mm/s; G = 918  mm/s; AMD = 854  mm/s). In contrast, glaucoma patients displayed longer DT (C = 510  ms; G = 552  ms; AMD = 528  ms) , MD (C = 935  ms; G = 1078  ms; AMD = 1060  ms) and higher PD (C = 1.14 [0.04]; G = 1.16 [0.05]; AMD = 1.12 [0.04]) suggesting difficulties with online control.
This preliminary analysis suggests that whilst glaucoma and AMD patients have deficits in reach to grasp movements compared with controls, they display distinct differences in movement planning and online control. Further work will explore how these relate to their specific visual deficiency.
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