advertisement
Abstract #15881 Published in IGR 2-3
Velocity model for Heidelberg retina flowmetry
HendricksonKlinische Monatsblätter für Augenheilkunde 2000; 217: 289-295
BACKGROUND: An application of scanning laser ophthalmoscopic flowmetry, Heidelberg retina flowmetry (HRF), is reported to quantify retinal perfusion faithfully. Indeed, without convincing regard for the fact that the method produced numerical values for such so-called 'velocity' (and subsequently calculates 'flow' and 'volume') with no physical units or proven real-life meaning, current clinical drug studies and patient care are being based on this method. To test the physical 'fidelity' of the HRF method, the author therefore devised a simple, reliable mechanical model to generate known velocities of movement of a test surface. MATERIAL AND METHODS: Movement of the circumferential surface of an 89-mm-diameter cylinder, belt-driven by a brass spindle with segments of increasing diameter, was analyzed with the HRF method. The true velocities (mm/sec) by which the surface passed the HRF's focal point were then determined using a stopwatch. A 10 x 2.5 measuring field and a 20 x 20 pixel analysis window were used. Measurements were made for horizontal, diagonal (45 and 135), and vertical motion at all the velocity settings of the model. RESULTS: The relationship between the real velocities of cylinder-surface motion and the corresponding HRF velocity values was nonlinear, an effect that increased significantly for diagonal and vertical motion. CONCLUSIONS: Considering the dependency on orientation of motion and the non-linearity of the relationship between HRF results and true velocity, as well as several other weaknesses discussed in this article, the question arises as to whether the validity of the HRF method should be reconsidered.LA: German
Dr. P. Hendrickson, Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115-5701, USA. Phillip_Hendrickson@hms.harvard.edu
Classification:
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)
