[The mechanical fundus perfusion model: blood flow velocity determined by ICG angiography and Heidelberg retina flowmetry].
BACKGROUND
Heidelberg Retina Flowmetry (HRF) is now popularly, perhaps even indiscriminately applied in eye research, without apparent concern for the fact that the results are given numerically, but without physical units.


METHODS
1) HRF: To challenge the HRF-device with known values of blood-flow velocity, a perfusion chamber with input and output connections was constructed of acrylic plastic. Three serial segments were milled to provide cross-sectional areas (1.93 mm2, 3.33 mm2, and 5.08 mm2) and accordingly decreasing, true, clinically representative flow-velocity values. Under a constant perfusion setting of a calibrated clinical infusion pump (Perfusor Secura FT, B. Braun Medical AG, Sempach, CH), heparinized human blood (P. H.) was pumped through the chamber, and the HRF-parameter, "VELOCITY" was measured within one image encompassing the three chamber segments, using a 20 degrees x 5 degrees-field and a 20 x 20-pixel measuring "window". 2) HRA: Immediately thereafter, our perfusion model was placed in front of the Heidelberg Retina Angiography device, the infusion pump started at the same constant level, and a 1 cc bolus of ICG dye was added to the blood. Digital ICG-angiography was then conducted, and the images analyzed on-screen.


RESULTS
In the three segments of the perfusion chamber, flow velocities determined ICG-angiographically were 11.5 mm/s, 6.7 mm/s, and 4.4 mm/s, respectively. The corresponding values for HRF- "VELOCITY" were 5.3, 4.2, and 3.4, respectively (no units).


CONCLUSIONS
Under identical perfusion conditions, the phenomenologically (ICG-angiographically) determined values of flow velocity in the 3 perfusion chamber segments ran similar to (but not numerically coincidental with) those determined for HRF-parameter "VELOCITY". Extrapolation of HRF-values to true physical units is, thus, feasible.
Universitäts-Augenspital Basel. hendrickson@ubaclu.unibas.ch
P
P
Hendrickson
T
T
DeMel
J C
JC
Peterson
D001783:Blood Flow Velocity / Q000502:physiology; D003287:Contrast Media; D005451:Fluorescein Angiography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007208:Indocyanine Green; D008955:Models, Cardiovascular; D012039:Regional Blood Flow / Q000502:physiology; D012161:Retinal Artery / Q000502:physiology*; D012169:Retinal Vein / Q000502:physiology*; D012212:Rheology
D003287:Contrast Media; D007208:Indocyanine Green
Mechanisches Fundusperfusions-Modell: Blutflussgeschwindigkeiten ermittelt durch ICG-Angiographie und Heidelberg Retina Flowmetry.