title: Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects.
abstract: OBJECTIVE
  To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours.
  
  
  METHODS
  The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter.
  
  
  RESULTS
  None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%.
  
  
  CONCLUSIONS
  These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency.
authors.affiliation: Department of Clinical Pharmacology, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Polska
authors.forename: K
authors.initials: K
authors.lastname: Polak
authors.forename: A
authors.initials: A
authors.lastname: Luksch
authors.forename: G
authors.initials: G
authors.lastname: Fuchsjager-Mayrl
authors.forename: V
authors.initials: V
authors.lastname: Petternel
authors.forename: O
authors.initials: O
authors.lastname: Findl
authors.forename: L
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure; D002829:Choroid / Q000098:blood supply*; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D007368:Interferometry / Q000379:methods; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry / Q000379:methods; D007834:Lasers; D008297:Male; D011673:Pulsatile Flow; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000379:methods