Contribution of stereopsis, vergence and accommodation to the performance of upper limb reaching and grasping movements

Abstract

Purpose : Binocular viewing is associated with a more efficient, accurate, and precise performance of upper limb movements in adults and children. Conversely, significantly poorer performance has been found with abnormal binocular viewing due to amblyopia or strabismus. It is currently unknown which aspects of binocular vision contribute to improved visuomotor behaviour. The purpose of this study was to characterize the contribution of stereopsis, vergence, and accommodation to the performance of a reaching, precision grasping and placement task.

Methods : Fifty-seven typically developing children (age: 8-14 years, 31 girls) were tested. Binocular visual function assessment included tests for stereoacuity, vergence (fusional vergence and facility), and accommodation (amplitude and facility). The prehension task involved picking up a small bead, and placing it onto a vertical needle. The following components of a prehension movement were identified: reach-to-bead, bead grasping, reach-to-needle, and bead placement on the needle. A stepwise multiple regression analysis was used to examine the contribution of stereoacuity, vergence, and accommodation to the performance of each component the movement sequence. Age was included as a covariate in the regression analysis to determine if changes in binocular function provide unique contribution to the model.

Results : Results from the regression showed that stereoacuity explained 16% of variance in grasp duration (R² = 0.16, p < 0.05), and vergence was associated with higher reach peak velocity, explaining 15% of variance (R² = 0.15, p < 0.05). Accommodation contributed to 10% of variance in total movement time, and 13% of variance in placement duration (p < 0.05). Age was found not to be a significant predictor of grasp duration or reach peak velocity but did explain 21% of variance in total movement time, and 27% of variance placement duration (p < 0.001).

Conclusions : Study findings indicate that different aspects of binocular vision contribute to the control of distinct phases of upper limb movements in typically developing children. Specifically, vergence was associated with higher peak velocity, stereoacuity was associated with grasp execution, and accommodation was associated with precision placement. These findings have implications when considering the effects of visual and oculomotor impairments on upper limb movement control.

This is a 2020 ARVO Annual Meeting abstract.