title: Pupil size and Perimetry--a pharmacological model using increment and decrement stimuli.
abstract: BACKGROUND
  To assess the influence of natural and pharmacologically induced pupil size fluctuations on differential luminance sensitivity threshold (DLS) using bright (increment) and dark (decrement) stimuli.
  
  
  METHODS
  Twelve healthy volunteers (20-30 years) were examined under the effect of phenylephrine 2%, dapiprazole 0.5%, and placebo. Pupil size was recorded by infra-red video camera in sessions without and with visual field examination (Tübingen Computer Campimeter). DLS was estimated at 9 locations within the central 20 degrees visual field, using bright and dark 26 min-of-arc-stimuli (10 cd/m(2) background, 4-2-1 dB thresholding strategy, four reversals).
  
  
  RESULTS
  There were substantial inter-individual differences in pupil size and pupil size fluctuations. Intra-individual differences were small. Independently of medication, pupil size fluctuations were reduced by more than one-third when a subject was undergoing perimetric examination. Pupil size affected DLS on its own (slope 0.21 dB/mm; 95% CI: 0.09-0.33 dB/mm), differently at different stimulus locations, and to a greater extent with increment than with decrement stimuli (slope difference 0.13 dB/mm; 95% CI: 0.00-0.26 dB/mm).
  
  
  CONCLUSIONS
  Campimetric examinations have a stabilising effect on pupil size fluctuations. Pupil size affects DLS with bright stimuli more than with dark stimuli; in normal young subjects this effect is not relevant for clinical or normative studies.
authors.affiliation: Department of Pathophysiology of Vision and Neuro-Ophthalmology, University Eye Hospital, Tuebingen University, Schleichstr. 12-16, 72076 Tübingen, Germany.
authors.forename: David D
authors.initials: DD
authors.lastname: Martin
authors.forename: Reinhard
authors.initials: R
authors.lastname: Vonthein
authors.forename: Helmut
authors.initials: H
authors.lastname: Wilhelm
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schiefer
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000328:Adult; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008954:Models, Biological; D010656:Phenylephrine / Q000494:pharmacology; D010781:Photography; D010879:Piperazines; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D012029:Refraction, Ocular / Q000502:physiology; D012684:Sensory Thresholds; D014230:Triazoles / Q000494:pharmacology; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D010879:Piperazines; D014230:Triazoles; D010656:Phenylephrine; C035289:dapiprazole