title: Influence of field size on pupil diameter under photopic and mesopic light levels.
abstract: OBJECTIVE
  We investigated the interaction between adapting field size and luminance on pupil diameter when cones alone (photopic) or rods and cones (mesopic) were active.
  
  
  METHODS
  Circular achromatic targets (1° to 24° diameter) were presented to eight young participants on a rectangular projector screen. The accommodative influence on pupil diameter was minimised using cycloplegia in the foveally fixating right eye and the consensual pupillary reflex was measured in the left eye. Target luminance was adjusted for each stimulus such that corneal flux density (product of field area and luminance) was constant at 3,600 cd.deg(2) m(-2) (photopic condition) and 1.49 cd.deg(2) m(-2) (mesopic condition).
  
  
  RESULTS
  There were no statistically significant effects of adaptive field size on pupil diameter for either condition.
  
  
  CONCLUSIONS
  If corneal flux density is kept constant, there will be no change in pupil diameter as the size of the stimulus field increases at either mesopic or photopic lighting levels up to at least 24° diameter.
authors.affiliation: School of Optometry and Institute of Health and Biomedical Innovation, Queensland University of Technology, Queensland, Australia. d.atchison@qut.edu.au
authors.forename: David A
authors.initials: DA
authors.lastname: Atchison
authors.forename: Cameron C
authors.initials: CC
authors.lastname: Girgenti
authors.forename: Giles M
authors.initials: GM
authors.lastname: Campbell
authors.forename: Jason P
authors.initials: JP
authors.lastname: Dodds
authors.forename: Tim M
authors.initials: TM
authors.lastname: Byrnes
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Zele
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008029:Lighting; D008297:Male; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*; D012016:Reference Values; D012160:Retina / Q000502:physiology*; D014794:Visual Fields; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult