Strategies for reducing variance in laser Doppler flowmetry measurements.
BACKGROUND
Scattering of blood flow data as assessed with laser Doppler flowmetry (LDF) in humans is a problem in many studies using this technique. We set out to reduce variability in LDF data by eliminating the effect of the total returning light level (DC) on LDF parameters in the choroid through partial regression analysis.


METHODS
In 20 healthy subjects, choroidal blood flow parameters were measured at different DC values using a portable confocal LDF device. We used two different strategies to reduce scattering of data eliminating the effect of yield, which is defined as DC/gain. On the one hand, we used a previously described method based on a third-order polynomial fit, which combines all obtained data. On the other hand, we applied a new method based on a linear fit for each individual subject.


RESULTS
Variability of data during changes in DC is higher for LDF parameters volume and flow than for velocity. Both methods were successful in reducing scattering of LDF parameters with varying DC.


CONCLUSIONS
The present study indicates that both methods to correct for changes in yield were successful in reducing the variability of LDF measurements. When systematic changes in DC occur after an intervention, one needs to be careful in interpreting the obtained data and it remains to be shown if either of the two techniques is capable of correcting for this effect. The approach presented here may, however, represent an effective, easily applicable and valid approach to reduce scattering of data from using LDF to assess blood flow in the posterior pole of the human eye.
Pemp
Berthold
B
Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
Maar
Noemi
N
Weigert
Guenther
G
Luksch
Alexandra
A
Resch
Hemma
H
Garhofer
Gerhard
G
Orgul
Selim
S
Schmetterer
Leopold
L
D000328:Adult; D001794:Blood Pressure; D002829:Choroid / Q000098:blood supply* / Q000000981:diagnostic imaging*; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry / Q000592:standards*; D016014:Linear Models; D008297:Male; D009898:Optic Disk / Q000098:blood supply* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D014463:Ultrasonography; D055815:Young Adult
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