title: Heading perception in patients with advanced retinitis pigmentosa.
abstract: OBJECTIVE
  We investigated whether retinis pigmentosa (RP) patients with residual visual field of < 100 degrees could perceive heading from optic flow.
  
  
  METHODS
  Four RP patients and four age-matched normally sighted control subjects viewed displays simulating an observer walking over a ground. In experiment 1, subjects viewed either the entire display with free fixation (full-field condition) or through an aperture with a fixation point at the center (aperture condition). In experiment 2, patients viewed displays of different durations.
  
  
  RESULTS
  RP patients' performance was comparable to that of the age-matched control subjects: heading judgment was better in the full-field condition than in the aperture condition. Increasing display duration from 0.5 s to 1 s improved patients' heading performance, but giving them more time (3 s) to gather more visual information did not consistently further improve their performance.
  
  
  CONCLUSIONS
  RP patients use active scanning eye movements to compensate for their visual field loss in heading perception; they might be able to gather sufficient optic flow information for heading perception in about 1 s.
mesh_terms: D005133:Eye Movements; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D016555:Matched-Pair Analysis; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology; D012174:Retinitis Pigmentosa / Q000503:physiopathology*; D013997:Time Factors; D014794:Visual Fields / Q000502:physiology; D014796:Visual Perception