title: Comparison of the Colvard pupillometer and the Zywave for measuring scotopic pupil diameter.
abstract: OBJECTIVE
  To evaluate the accuracy and repeatability of two pupillometers.
  
  
  METHODS
  Two pupillometers, the Colvard and Zywave, were used to measure scotopic pupil diameter for 64 consecutive patients. Accuracy and repeatability were assessed by two independent examiners and statistical analysis was performed using the comparison method described by Bland and Altman.
  
  
  RESULTS
  Mean scotopic pupil diameter was 5.96 +/- 0.69 mm with the Colvard pupillometer and 5.77 +/- 0.85 mm with the Zywave. The difference between the Colvard and Zywave measurements was 0.21 +/- 0.56 mm (P < .001). The coefficient of interrater repeatability was smaller for the Colvard (0.59) than for the Zywave (1.17). The mean difference between the pupillometers for each examiner was 0.17 +/- 0.47 mm (P < .01) for examiner 1 and 0.26 +/- 0.64 mm (P < .01) for examiner 2.
  
  
  CONCLUSIONS
  Scotopic pupil diameter measured with the Zywave was statistically but not clinically significantly smaller than that measured with the Colvard pupillometer. The Zywave produced an inter-rater repeatability comparable to other devices although not as good as the Colvard pupillometer.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Kowloon, Hong Kong. arthurcheng@cuhk.edu.hk
authors.forename: Arthur C K
authors.initials: AC
authors.lastname: Cheng
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D001837:Body Weights and Measures; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology*; D015203:Reproducibility of Results