title: Influence of background complexity on visual sensitivity and binocular summation using patterns with and without noise.
abstract: OBJECTIVE
  To investigate how background complexity influences visual sensitivity and binocular summation.
  
  
  METHODS
  Using two noise backgrounds (noise-sparse and noise-dense) and two corresponding noise-free backgrounds with the same luminance for each noise background, monocular and binocular thresholds were measured in six visually normal subjects (average age, 27.3 ± 1.1 years). The noise-sparse and noise-dense backgrounds respectively had 312 and 936 white-light dots projected on them-the same size white-light dots (0.431° of visual angle) as those that were used for the white-spot target in the threshold measurement. The target was tested at the fovea and at 3° intervals on the 45°, 135°, 225°, and 315° meridians. A total of 25 locations were tested.
  
  
  RESULTS
  The monocular threshold for the noise-dense background was higher than that for its corresponding noise-free background, with significant differences seen at 15° and 18° (P < 0.01). No significant differences in the binocular threshold were seen, either between the noise-dense and its corresponding backgrounds or between the noise-sparse and its corresponding backgrounds. The binocular summation ratios for both noise backgrounds were significantly higher than the ratios for the noise-free backgrounds, and the difference increased with eccentricity, with significances seen at 15° and 18° (P < 0.01).
  
  
  CONCLUSIONS
  Only the monocular threshold increases with background complexity. The binocular summation increases with background complexity in the periphery. When the background becomes more complex and the monocular visual processing reaches its limit, binocular interaction functions efficiently.
authors.affiliation: Department of Ophthalmology, Kinki University Faculty of Medicine, Osaka, Japan. akemi.wakayama@sayama.med.kindai.ac.jp
authors.forename: Akemi
authors.initials: A
authors.lastname: Wakayama
authors.forename: Chota
authors.initials: C
authors.lastname: Matsumoto
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Ohmure
authors.forename: Masahiko
authors.initials: M
authors.lastname: Inase
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Shimomura
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D012684:Sensory Thresholds / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*