title: Analysis of mean retinal transit time from fluorescein angiography in human eyes: normal values and reproducibility.
abstract: OBJECTIVE
  To evaluate three different techniques to quantify retinal blood flow transit times in normal human eyes from fluorescein angiograms.
  
  
  METHODS
  Fluorescein angiograms were recorded on two different occasions in 18 normal individuals with a scanning laser ophthalmoscope. The angiograms were digitized (5 frames per second) and the images were aligned. Mean transit times (MTT) were analysed with a newly developed technique based on an impulse-response analysis (MTTIR) and again with the conventional technique (MTTSLOPE). Arterio-venous passage times (AVP) were also calculated.
  
  
  RESULTS
  At the first determination, mean values (SD) for MTTIR, MTTSLOPE, and AVP were 3.22 (0.78), 4.88 (1.86), and 1.46 (0.57) seconds, respectively. Detection of an increase of 25% with a power of 80% requires groups of 12, 86 and 17 individuals for the three techniques, respectively.
  
  
  CONCLUSIONS
  Mean transit time is a well-defined physiological parameter. The technique based on impulse-response analysis allows for analysis of even badly defined dye curves. We found this technique to be superior to the conventional technique in terms of reproducibility.
authors.affiliation: Department of Neuroscience, Opthalmology, University Hospital, uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Bjärnhall
authors.forename: O
authors.initials: O
authors.lastname: Mäepea
authors.forename: G O
authors.initials: GO
authors.lastname: Sperber
authors.forename: C
authors.initials: C
authors.lastname: Lindén
authors.forename: E
authors.initials: E
authors.lastname: Mönestam
authors.forename: A
authors.initials: A
authors.lastname: Alm
mesh_terms: D000328:Adult; D001775:Blood Circulation; D001776:Blood Circulation Time; D001783:Blood Flow Velocity; D005260:Female; D005451:Fluorescein Angiography / Q000379:methods*; D006801:Humans; D008297:Male; D019721:Ophthalmoscopes; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000502:physiology*