Reaching and grasping with restricted peripheral vision.

Objective: To investigate how prehensile movements, such as reaching and grasping, are affected by different fields of view when both haptic and visual information are available.

Methods: Ten volunteers with normal vision (mean age 24.5 years) participated. Subjects picked up an object with a full monocular field of view (FOV) and with two different sizes of pinholes which simulated a central FOV of 23 degrees and 11 degrees respectively. The Vicon motion analysis system was used to record and reconstruct the 3D-kinematic data. The kinematic parameters measured were total time of the movement, maximum velocity, time to maximum velocity, deceleration time, maximum grip aperture, time to maximum grip aperture and time taken after maximum grip aperture.

Results: Restricting the FOV affected both the transport and grasp components of the movement. The maximum velocity decreased (p = 0.008) and the maximum grip aperture increased (p = 0.003) with both restricted FOV when compared with the full field. The execution or on-line control of both reach and grasp components were also longer (p = 0.005 and p = 0.002 respectively) for the 11 degrees FOV only.

Conclusions: Reducing the FOV to 11 degrees (an absence of peripheral vision) affects the planning and execution of the reach and the grasp component of the movement. Restricting the FOV to 23 degrees of central vision (with some peripheral cues present) affects only the planning of the reach and grasp component of the movement. Peripheral visual cues are therefore more important for the on-line control than for the planning of the movement. The findings of this study have important clinical implications in patients who suffer from ocular diseases in which peripheral vision gradually decreases.