Exploring eye-hand coordination in central field loss with virtual reality.

Eye-hand coordination relies on accurate depth perception and gaze control, both of which are impaired in central field loss (CFL). Using an immersive VR paradigm, we examined how CFL affects gaze and hand control during a dynamic 3D butterfly-catching task. Seven patients with CFL and 13 controls performed three conditions: eye-tracking only (following the butterfly with gaze), hand-tracking (keeping the butterfly centered in a virtual net), and catching (capturing it). Patients performed all conditions binocularly and monocularly, while controls additionally performed them with a simulated scotoma. Binocular viewing led to faster catching times, and to more accurate gaze in both patients and controls compared to monocular viewing, with a greater binocular advantage in patients. Vergence analyses revealed that gaze followed the depth of the target more accurately during active catching in both groups, but only under binocular viewing, indicating that motor engagement refines depth estimates when binocular disparity is available. For hand-tracking, the ability to track the target in depth was particularly impacted in patients under monocular viewing, again suggesting a dependence on disparity information. Taken together, our VR studies reveal compensatory eye-hand strategies in CFL that support depth tracking under binocular viewing conditions that mimic real life.