title: Impact of simulated central scotomas on visual search in natural scenes.
abstract: OBJECTIVE
  In performing search tasks, the visual system encodes information across the visual field at a resolution inversely related to eccentricity and deploys saccades to place visually interesting targets upon the fovea, where resolution is highest. The serial process of fixation, punctuated by saccadic eye movements, continues until the desired target has been located. Loss of central vision restricts the ability to resolve the high spatial information of a target, interfering with this visual search process. We investigate oculomotor adaptations to central visual field loss with gaze-contingent artificial scotomas.
  
  
  METHODS
  Spatial distortions were placed at random locations in 25° square natural scenes. Gaze-contingent artificial central scotomas were updated at the screen rate (75 Hz) based on a 250 Hz eye tracker. Eight subjects searched the natural scene for the spatial distortion and indicated its location using a mouse-controlled cursor.
  
  
  RESULTS
  As the central scotoma size increased, the mean search time increased [F(3,28) = 5.27, p = 0.05], and the spatial distribution of gaze points during fixation increased significantly along the x [F(3,28) = 6.33, p = 0.002] and y [F(3,28) = 3.32, p = 0.034] axes. Oculomotor patterns of fixation duration, saccade size, and saccade duration did not change significantly, regardless of scotoma size.
  
  
  CONCLUSIONS
  There is limited automatic adaptation of the oculomotor system after simulated central vision loss.
authors.affiliation: Department of Ophthalmology, Harvard Medical School, Schepens Eye Research Institute, Boston, Massachusetts 02114, USA. lee.mcilreavy@schepens.harvard.edu
authors.forename: Lee
authors.initials: L
authors.lastname: McIlreavy
authors.forename: Jozsef
authors.initials: J
authors.lastname: Fiser
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Bex
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D005500:Follow-Up Studies; D006801:Humans; D008568:Memory / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D012438:Saccades / Q000502:physiology*; D012607:Scotoma / Q000503:physiopathology*; D012683:Sensory Deprivation; D014794:Visual Fields; D055815:Young Adult