Deficits in Reach Planning and On-Line Grasp Control in Adults With Amblyopia

Area of Science:

• Neuroscience
• Ophthalmology
• Motor Control

Background:

• Amblyopia, a developmental disorder, causes reduced vision in one eye.
• Individuals with amblyopia often exhibit motor control deficits, including in prehension tasks.

Purpose of the Study:

• To investigate whether motor deficits in adults with amblyopia during reach-to-grasp tasks stem from impaired feedforward planning or online visual feedback control.
• To differentiate between planning and feedback deficits in amblyopic individuals' prehension movements.

Main Methods:

• Twenty-one adults with amblyopia and 21 controls performed reach-grasp-lift tasks with objects of varying sizes and distances.
• Movement kinematics and errors were analyzed under different visual conditions: planning only (no feedback) versus planning and execution (full feedback).
• Vision conditions included binocular, dominant eye, and amblyopic eye viewing.

Main Results:

• Amblyopic adults showed significant impairments in reach-to-grasp tasks compared to controls across all visual conditions.
• Planning deficits were pronounced, particularly when using the amblyopic eye, with increased movement times and errors.
• Online visual feedback partially improved reach planning but did not fully resolve grasp control issues, which were exacerbated by poor binocularity.

Conclusions:

• Adults with amblyopia have difficulties creating accurate internal spatial representations for movement planning, primarily affecting the reach phase.
• Impaired online grasp control in amblyopia is linked to reduced binocular vision and stereopsis.
• These findings highlight distinct planning and feedback control deficits in amblyopic individuals' motor behavior.