Are hemianopic reading and visual exploration impairments visually elicited? New insights from eye movements in simulated hemianopia.

Hemianopic reading and visual exploration impairments are well-known clinical phenomena. Yet, it is unclear whether they are primarily caused by the hemianopic visual field defect itself or by additional brain injury preventing efficient spontaneous oculomotor adaptation. To establish the extent to which these impairments are visually elicited we simulated unilateral homonymous hemianopia in healthy participants, using a gaze-contingent display paradigm, and investigated its effect on reading and visual exploration. We demonstrate that simulated hemianopia induces the reading and visual exploration impairments of hemianopic patients. Over time, however, all participants showed efficient spontaneous oculomotor adaptation to the visual-sensory loss which improved their reading and visual exploration performance. Our results suggest that the hemianopic visual field defect is a major component of the chronic impairments of reading and visual and exploration found in hemianopic patients although it may not be their sole cause.