title: Does pupil dilation influence subfoveal choroidal laser Doppler flowmetry?
abstract: OBJECTIVE
  The aim of this study was to assess (i) whether pupil dilation with tropicamide influences subfoveal choroidal blood flow, as assessed by continuous laser Doppler flowmetry (LDF) and (ii) if this is the case, whether the effect is due to a haemodynamic response of the drug-induced dilation.
  
  
  METHODS
  Following the instillation of one drop of 1% tropicamide in one eye of 18 healthy, nonsmoking volunteers (age 20-25 years), the subfoveal choroidal LDF parameters (Vel, Vol and ChBF) were recorded during 30 min, at 3-min intervals under two paradigms: through an artificial pupil (4 mm diameter) placed in front of the cornea (P1) and without this artificial pupil (P2).
  
  
  RESULTS
  Tropicamide increased the pupil diameter from 3.3 ± 0.4 mm (mean ± SD) to 8.3 ± .4 mm. Full dilation was reached at ~24 min. During this period of time, linear regression analysis demonstrated that none of the LDF parameters varied significantly (p > 0.05), either under P1 or P2. Based on a group of 12 subjects, the smallest (%) change in the mean value of ChBF (ChBFm ) that would be detectable (sensitivity of the method, S) was found to be 2% for P1 and 6% for P2. The average coefficient of variation of ChBFm based on eight measurements during dilation was greater for P2 than for P1 by a factor of approximately 2.
  
  
  CONCLUSIONS
  Tropicamide had no significant influence on the subfoveal choroidal LDF parameters measured by continuous LDF during pupil dilation. Furthermore, pupil dilation did not affect ChBFm by more than the calculated minimum percentage change of 6% detectable with our method.
authors: Department of Information Engineering, University of Modena and Reggio Emilia, Modena, ItalyProf.Emeritus, University of Lausanne, Lausanne, SwitzerlandDepartment of Specialistic Surgery and Anesthesiology Science, Ophthalmology Unit, University of Bologna, Bologna, Italy.
authors: Nithiyanantham
authors: N
authors: Palanisamy
authors: Charles E
authors: CE
authors: Riva
authors: Luigi
authors: L
authors: Rovati
authors: Mauro
authors: M
authors: Cellini
authors: Corrado
authors: C
authors: Gizzi
authors: Ernesto
authors: E
authors: Strobbe
mesh_terms: D000328:Adult; D002829:Choroid / Q000098:blood supply*; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage*; D009883:Ophthalmic Solutions; D011680:Pupil / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D014331:Tropicamide / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D009184:Mydriatics; D009883:Ophthalmic Solutions; D014331:Tropicamide
keywords: LDF parameters; fundus camera-based LDF; pupil dilation; subfoveal choroidal haemodynamic; tropicamide