title: Asymmetry in the Collision Judgments of People With Homonymous Field Defects and Left Hemispatial Neglect.
abstract: OBJECTIVE
  Although the impact of homonymous visual field defects (HFDs) on mobility has been investigated previously, the emphasis has been on obstacle detection. Relatively little is known about HFD patients' ability to judge collisions once an obstacle is detected. We investigated this using a walking simulator.
  
  
  METHODS
  Patients with HFDs (n = 29) and subjects with normal vision (NV; n = 21) were seated in front of a large screen on which a visual simulation of walking was displayed. They made collision judgments for a human figure that appeared for 1 second at lateral offsets from the virtual walking path. A perceived-collision threshold was calculated for right and left sides.
  
  
  RESULTS
  Symmetrical collision thresholds (same on left and right sides) were measured for participants with NV (n = 21), and right (n = 9) and left (n = 7) HFD without hemispatial neglect. Participants with left neglect (n = 10) showed significant asymmetry with thresholds smaller (compared to the NV group and other HFD groups) on the blind (P < 0.001) and larger on the seeing (P = 0.05) sides. Despite the asymmetry, the overall width of the zone of perceived collision risk was not different, suggesting a relatively uniform rightward deviation in judgments of the left neglect group.
  
  
  CONCLUSIONS
  Left neglect was associated with rightward asymmetry in collision judgments, which may cause collisions on the left side even when an obstacle is detected. These behaviors may represent the spatial misperceptions in body midline described previously in patients with left neglect.
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States 2Spaulding Rehabilitation Hospital, Boston, Massachusetts, United States.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Houston
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Russell L
authors.initials: RL
authors.lastname: Woods
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Goldstein
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Eli
authors.initials: E
authors.lastname: Peli
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Gang
authors.initials: G
authors.lastname: Luo
authors.affiliation: Schepens Eye Research Institute Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Alex R
authors.initials: AR
authors.lastname: Bowers
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006423:Hemianopsia / Q000503:physiopathology*; D006801:Humans; D007600:Judgment / Q000502:physiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D010468:Perceptual Disorders / Q000503:physiopathology*; D012684:Sensory Thresholds / Q000502:physiology; D014794:Visual Fields / Q000502:physiology*; D016138:Walking