title: [Spatial summation: its topography in the central visual field].
abstract: OBJECTIVE
  Luminance (L) and area (A) of the stimulus are related by the equation LxAk=constant. We evaluated the k value in 66 positions of the central visual field.
  
  
  METHODS
  Ten eyes of 10 healthy subjects were examined for conventional luminous thresholds at 66 positions of the central visual field with the TOP strategy using Goldmann sizes 4, 3.5, 3, 2.5 and 1.9 in the PULSAR perimeter.
  
  
  RESULTS
  The k value increased in a lineal manner from the centre towards the periphery (slope=0.01 per degree, average k=0.616, r=0.98, p<0.01) but with unequal slopes at the different meridians. In the inferior hemi-fields it was higher (k=0.657) than in the superior hemi-fields (k=0.574). The k value at the supero-nasal hemifields is quite similar to that found at the paracentral region, and maximum at the temporal inferior region.
  
  
  CONCLUSIONS
  Spatial summation in the central visual field has specific values for different positions.
authors.affiliation: Hospital Universitario de Canarias, Universidad de La Laguna, Islas Canarias, Spain. martagh@jet.es
authors.forename: M
authors.initials: M
authors.lastname: González-Hernández
authors.forename: M
authors.initials: M
authors.lastname: González-de-la-Rosa
authors.forename: A
authors.initials: A
authors.lastname: Pareja
authors.forename: V
authors.initials: V
authors.lastname: Lozano
authors.forename: F
authors.initials: F
authors.lastname: Mesa
mesh_terms: D005260:Female; D005584:Fovea Centralis / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D014786:Vision Disorders / Q000503:physiopathology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*