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Konstantin Gugleta, Selim Orgül, Ivo Flammer, Doina Gherghel, Josef Flammer; Reliability of Confocal Choroidal Laser Doppler Flowmetry. Invest. Ophthalmol. Vis. Sci. 2002;43(3):723-728.
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purpose. To assess the variability in choroidal laser Doppler flowmetry (LDF).
methods. Five measurements of choroidal blood flow were obtained on 5 days in
both eyes of 10 subjects. Reliability, sensitivity, and sample size
calculations were performed. Yield, the intensity of the returning
light (direct current [DC]) divided by the signal amplification
(gain) used during recording, was calculated (yield = DC/gain).
The correlation between yield and the LDF parameters velocity, volume,
and flux was analyzed. Reliability, sensitivity, and sample size
calculations were repeated after correcting for this relationship. The
influence of different light-scattering properties on the returning
signal was assessed in a model eye.
results. Yield and the LDF parameters, velocity, volume, and flux, correlated
significantly in a regression model. After the influence of yield was
partialized out, reliability, reproducibility, sensitivity, and
statistical power improved markedly. The high reliability of yield in a
given eye (87%) suggests, that, besides varying recording settings on
different days, individual specific scattering properties within the
eye influence LDF measurements. Comparison of model eye data with human
data disclosed a low signal-to-noise ratio with decreasing yield.
Correcting for yield did not affect the sensitivity to blood flow
changes induced by hypercapnia or a suction cup.
conclusions. Tissue-scattering properties alter the characteristics of the returning
light, and recording settings affect the outcome of the analysis of the
returning light during LDF measurements. Partializing out the influence
of yield markedly improves the reproducibility of choroidal
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