title: Comparison of 2 monocular pupillometers and an autorefractor for measurement of the dark-adapted pupil diameter.
abstract: OBJECTIVE
  To compare the performance of the Marco Nidek ARK-530A autorefractor pupillometer function and the Keeler PupilScan II pupillometer (study pupillometer) against the clinical standard NeurOptics PLR-200 pupillometer (standard pupillometer) for measurement of the dark-adapted pupil diameter.
  
  
  METHODS
  Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.
  
  
  METHODS
  Evaluation of diagnostic test or technology.
  
  
  METHODS
  Subjects aged 20 to 60 years were dark-adapted for 2 minutes at 1 lux ambient illumination. Accommodation was controlled through distance fixation. The dark-adapted pupil diameter was measured with the standard pupillometer, then the study pupillometer, then the autorefractor. Results were compared using Bland-Altman graphs.
  
  
  RESULTS
  The autorefractor underestimated the dark-adapted pupil diameter by a mean of 1.03 mm (range 0.0 to 2.3 mm). Thirty-four (85%) measurements were at least 0.5 mm smaller than the corresponding standard pupillometer values, and 16 (40%) were more than 1.0 mm smaller. Observer experience did not improve accuracy. The study pupillometer underestimated the dark-adapted pupil diameter by a mean of 0.31 mm (range 0.0 to 0.9 mm). Ten (25%) measurements were at least 0.5 mm smaller than the standard pupillometer values. Accuracy improved in the final 10 subjects (study pupillometer smaller; mean difference 0.16 mm; range 0.0 to 0.4 mm).
  
  
  CONCLUSIONS
  The autorefractor pupillometry function had an unpredictable negative bias (variable underestimation of dark-adapted pupil diameter). The study pupillometer had a slight negative bias but required significant examiner skill and knowledge of normal pupil movement to obtain a valid result. Neither device was sufficiently accurate for confident surgical planning or clinical diagnosis.
  
  
  BACKGROUND
  Neither author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: Cabarrus Eye Center, Concord, North Carolina, USA. sbrownmd@cabarruseye.com
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Brown
authors.forename: Jay C
authors.initials: JC
authors.lastname: Bradley
mesh_terms: D000328:Adult; D003623:Dark Adaptation; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology*; D055815:Young Adult