OBJECTIVE: To evaluate three different techniques to quantify retinal blood flow transit times in normal human eyes from fluorescein angiograms. SUBJECTS AND 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.
OBJECTIVE: To evaluate three different techniques to quantify retinal blood flow transit times in normal human eyes from fluorescein angiograms. SUBJECTS AND 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.