title: The magnitude and distribution of open-loop accommodation using three different methods of opening the loop.
abstract: OBJECTIVE
  The present study examines the magnitude, distribution, and relationship of open-loop accommodation obtained using the three most common methods of opening the accommodation loop.
  
  
  METHODS
  Open-loop accommodation was measured in 93 young, emmetropic subjects using a Canon R1 objective infrared optometer, and the accommodation loop was opened using the following methods: (1) dark empty field (DA), (2) bright empty field (BA), and (3) viewing a target through a small artificial pupil (PA).
  
  
  RESULTS
  PA was found to elicit significantly (p = 0.0001) higher values of open-loop accommodation than either DA or BA and demonstrated a much wider distribution of values than DA or BA. A further experiment demonstrated that the higher PA was attributable to the proximal effect of placing a small artificial pupil close to the eye.
  
  
  CONCLUSIONS
  Our results suggest that using a small artificial pupil to open the accommodation loop may not produce a veridical measure of open-loop accommodation.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, Scotland.
authors.forename: L S
authors.initials: LS
authors.lastname: Gray
authors.forename: N C
authors.initials: NC
authors.lastname: Strang
authors.forename: N
authors.initials: N
authors.lastname: Winfield
authors.forename: B
authors.initials: B
authors.lastname: Gilmartin
authors.forename: B
authors.initials: B
authors.lastname: Winn
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D003623:Dark Adaptation; D006801:Humans; D008027:Light; D009907:Optometry / Q000379:methods*; D011680:Pupil