title: Distribution of photopic pupil diameter in the Tehran eye study.
abstract: OBJECTIVE
  To determine the photopic pupil diameter and its determinants in a sample derived from a population-based survey in Tehran.
  
  
  METHODS
  In a cross-sectional study with a stratified random cluster sampling approach, 410 people age 14 years and over were selected from those residing in the first four municipality districts of Tehran after applying exclusion criteria, and 800 eyes (399 right eyes and 401 left eyes) were examined with the Orbscan II. The main outcome measure was the mean pupil diameter under photopic conditions, and possible correlations with potential determinants were evaluated through linear regression analyses. The design effect of a cluster sampling approach was observed and adjusted for.
  
  
  RESULTS
  The mean age of the participants was 40.6 +/- 16.8 years and 38.8% were male. The mean photopic pupil diameter (PPD) was 3.70 mm (range 2.30 to 5.10; 95% confidence interval (CI) 3.62 to 3.78). The mean PPD was 3.67 mm (95% CI, 3.54 to 3.81) in men and 3.72 mm (95% CI, 3.63 to 3.81) in women (p = 0.481). There was a significant reduction of 0.021 mm in PPD per year of aging (r = -0.49, p < 0.001). There was also a significant inverse correlation between PPD and spherical equivalent (r = -0.12, p = 0.034), while there was 0.66-mm increase in PPD with every 1.0-mm increase in the anterior chamber depth (ACD) (p < 0.001). Anisocoria, defined as a pupil diameter difference more than 0.4 mm between two eyes, was observed in 12.2% of the study population.
  
  
  CONCLUSIONS
  While the mean PPD measured with the Orbscan II was 3.70 mm in a sample derived from a population-based survey in Tehran, the scarcity of similar studies and reports concerning the pupil diameter measured with the Orbscan II makes it difficult to draw eligible comparisons. The pupil diameter has reverse correlations with age and spherical equivalent, a direct correlation with ACD, but is not correlated with gender.
authors.affiliation: Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Kamran
authors.initials: K
authors.lastname: Yazdani
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.forename: Kazem
authors.initials: K
authors.lastname: Mohammad
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000293:Adolescent; D000328:Adult; D015875:Anisocoria / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005127:Eye Color; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D007498:Iris / Q000033:anatomy & histology*; D008027:Light; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000528:radiation effects*; D055815:Young Adult