Comparison of retinal transit times and retinal blood flow: a study in monkeys.
OBJECTIVE
To determine the correlation between transit times of retinal blood flow calculated from fluorescein angiograms and retinal blood flow determined by the microsphere method.


METHODS
Two fluorescein angiograms were obtained in each eye of six monkeys, followed by determination of retinal blood flow with labeled microspheres. Angiograms in 10 eyes were analyzed for mean transit time (MTT) and arteriovenous passage time (AVP). MTT was determined in two ways: from dye curves reconstructed by extrapolation of semilogarithmic plots of the recorded curves (MTT(slope)) and by a new technique based on an impulse-response analysis (MTT(ir)).


RESULTS
Mean values (+/-SD) for retinal blood flow in 10 eyes were 23.2 +/- 6.9 mg/min. Corresponding values for MTT(ir), MTT(slope), and AVP were 2.22 +/- 0.38, 4.89 +/- 5.89, and 1.08 +/- 0.14 seconds. There was a weak, but not statistically significant, correlation between retinal blood flow and MTT(ir) (r = -0.60, P = 0.06) but no useful correlation between retinal blood flow and either MTT(slope) or AVP.


CONCLUSIONS
The relationship between retinal blood flow and transit times determined from fluorescein angiograms is weak. Of the three transit parameters tested, MTT(ir), determined with the recently developed impulse-response technique, had the best correlation with retinal blood flow. Further studies are needed to determine the ability of these transit parameters to detect a change in retinal blood flow and the possibility that transit times may provide useful clinical information unrelated to absolute values of retinal blood flow.
Department of Neuroscience, Ophthalmology, Uppsala University Hospital, S-701 85 Uppsala, Sweden.
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Tomic
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Mäepea
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Sperber
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Alm
D000818:Animals; D001776:Blood Circulation Time; D001783:Blood Flow Velocity / Q000502:physiology; D005260:Female; D005451:Fluorescein Angiography; D008252:Macaca fascicularis; D008297:Male; D008863:Microspheres; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000502:physiology*; D013997:Time Factors