title: Factors affecting light-adapted pupil size in normal human subjects.
abstract: OBJECTIVE
  To investigate the effect of age, gender, refractive error, and iris color on light-adapted pupil size in humans.
  
  
  METHODS
  Pupil diameters of 91 subjects (age range, 17 to 83 years) with normal, healthy eyes were measured using an objective infrared-based continuous recording technique. Five photopic ocular illuminance levels were used (2.15 to 1050 lumens m-2), and the accommodative status of each subject was precisely controlled at a constant level.
  
  
  RESULTS
  Pupil size decreased linearly as a function of age at all illuminance levels. Even at the highest illuminance level, there was still a significant effect of age upon pupil size. The rate of change of pupil diameter with age decreased from 0.043 mm per year at the lowest illuminance level to 0.015 mm per year at the highest. In addition, the variability between pupil sizes of subjects of the same age decreased by a factor of approximately two as luminance was increased over the range investigated. Pupil size was found to be independent of gender, refractive error, or iris color (P > 0.1).
  
  
  CONCLUSIONS
  Of the factors investigated, only chronologic age had a significant effect on the size of the pupil. The phenomenon of senile miosis is present over a wide range of ocular illuminance levels.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, United Kingdom.
authors.forename: B
authors.initials: B
authors.lastname: Winn
authors.forename: D
authors.initials: D
authors.lastname: Whitaker
authors.forename: D B
authors.initials: DB
authors.lastname: Elliott
authors.forename: N J
authors.initials: NJ
authors.lastname: Phillips
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology; D000221:Adaptation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D005127:Eye Color / Q000502:physiology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology; D012737:Sex Factors