Assessment of choroidal blood flow using laser speckle flowgraphy

Giacomo Calzetti, Klemens Fondi, Ahmed M Bata, Nikolaus Luft, Piotr A Wozniak, Katarzyna J Witkowska, Matthias Bolz, Alina Popa-Cherecheanu, René M Werkmeister, Doreen Schmidl, Gerhard Garhöfer, Leopold Schmetterer, Giacomo Calzetti, Klemens Fondi, Ahmed M Bata, Nikolaus Luft, Piotr A Wozniak, Katarzyna J Witkowska, Matthias Bolz, Alina Popa-Cherecheanu, René M Werkmeister, Doreen Schmidl, Gerhard Garhöfer, Leopold Schmetterer

Abstract

Background/aims: There is considerable interest in novel techniques to quantify choroidal blood flow (CBF) in humans. In the present study, we investigated a novel technique to measure CBF based on laser speckle flowgraphy (LSFG) in healthy subjects.

Methods: This study included 31 eyes of 31 healthy, non-smoking subjects aged between 19 and 74 years. A commercial LSFG instrument was used to measure choroidal vessel diameter (CVD) and relative flow volume (RFV) in choroidal vessels that were identified on fundus photos, an approach that was used previously only for retinal vessels. The reproducibility and the effect of isometric exercise on these parameters were investigated. The latter was compared with measurement of subfoveal CBF using laser Doppler flowmetry (LDF).

Results: Intraclass correlation coefficients for CVD and RFV were higher than 0.8 indicating excellent reproducibility. During isometric exercise, we observed an increase in ocular perfusion pressure of approximately 60% (P<0.001). The increase in RFV and CBF was lower, but also highly significant versus baseline (at minute 6 of isometric exercise: RFV 10.5%±4.2%, CBF 8.3%±3.6%; P<0.001 each) indicating choroidal autoregulation.

Conclusion: LSFG may be a novel approach to study blood flow in choroidal vessels. Data are reproducible and show good agreement with LDF data.

Trial registration number: NCT02102880, Results.

Keywords: choroid; imaging; physiology.

Conflict of interest statement

Competing interests: None declared.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Figures

Figure 1
Figure 1
Identification of choroidal blood vessels for Laser Speckle Flowgraphy (LSFG) analysis. (A) First a choroidal vessel is identified based on a fundus photograph. The choroidal vessel of interest is shown inside a white rectangular band that is manually placed. (B) The presence of the choroidal vessel is then confirmed at the LSFG intensity image. (C) In the perfusion map, a rectangular white band is traced across the vessel which appears red because of the high intravascular blood velocity.
Figure 2
Figure 2
Ocular perfusion pressure (OPP), relative flow volume (RFV) and choroidal vessel diameter (CVD) during isometric exercise. Data are expressed as per cent change from baseline. Data are presented as means±SD (n=10).
Figure 3
Figure 3
Ocular perfusion pressure (OPP) and choroidal blood flow (CBF) during isometric exercise. Data are expressed as per cent change from baseline. Data are presented as means±SD (n=10).

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