Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Canada.
PLoS One. 2012;7(2):e31075. doi: 10.1371/journal.pone.0031075. Epub 2012 Feb 17.
Impairment of spatiotemporal visual processing in amblyopia has been studied extensively, but its effects on visuomotor tasks have rarely been examined. Here, we investigate how visual deficits in amblyopia affect motor planning and online control of visually-guided, unconstrained reaching movements.
Thirteen patients with mild amblyopia, 13 with severe amblyopia and 13 visually-normal participants were recruited. Participants reached and touched a visual target during binocular and monocular viewing. Motor planning was assessed by examining spatial variability of the trajectory at 50-100 ms after movement onset. Online control was assessed by examining the endpoint variability and by calculating the coefficient of determination (R(2)) which correlates the spatial position of the limb during the movement to endpoint position.
Patients with amblyopia had reduced precision of the motor plan in all viewing conditions as evidenced by increased variability of the reach early in the trajectory. Endpoint precision was comparable between patients with mild amblyopia and control participants. Patients with severe amblyopia had reduced endpoint precision along azimuth and elevation during amblyopic eye viewing only, and along the depth axis in all viewing conditions. In addition, they had significantly higher R(2) values at 70% of movement time along the elevation and depth axes during amblyopic eye viewing.
Sensory uncertainty due to amblyopia leads to reduced precision of the motor plan. The ability to implement online corrections depends on the severity of the visual deficit, viewing condition, and the axis of the reaching movement. Patients with mild amblyopia used online control effectively to compensate for the reduced precision of the motor plan. In contrast, patients with severe amblyopia were not able to use online control as effectively to amend the limb trajectory especially along the depth axis, which could be due to their abnormal stereopsis.
弱视患者的时空视觉处理能力受损已得到广泛研究，但很少有研究检查其对视动任务的影响。在这里，我们研究弱视中的视觉缺陷如何影响视觉引导的无约束伸手运动的运动规划和在线控制。
招募了 13 名轻度弱视患者、13 名重度弱视患者和 13 名视力正常的参与者。参与者在双眼和单眼观察期间伸手触摸视觉目标。通过检查运动开始后 50-100 毫秒轨迹的空间变异性来评估运动规划。通过检查端点变异性并计算决定系数（R²）来评估在线控制，R² 相关肢体在运动过程中的空间位置与端点位置。
弱视患者在所有观察条件下的运动计划精度均降低，表现为轨迹早期的伸展变异性增加。轻度弱视患者和对照组参与者的端点精度相当。重度弱视患者仅在弱视眼观察时，在方位角和仰角以及所有观察条件下在深度轴上的端点精度降低。此外，他们在弱视眼观察时的运动时间的 70%处沿仰角和深度轴的 R² 值明显更高。
弱视引起的感觉不确定性导致运动计划精度降低。实施在线校正的能力取决于视觉缺陷的严重程度、观察条件和伸手运动的轴。轻度弱视患者有效地使用在线控制来补偿运动计划精度的降低。相比之下，重度弱视患者无法有效地使用在线控制来修正肢体轨迹，尤其是在深度轴上，这可能是由于他们的立体视异常所致。
