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Clinical Trial
. 2018 Nov 28;13(11):e0207525.
doi: 10.1371/journal.pone.0207525. eCollection 2018.

Evaluation of flicker induced hyperemia in the retina and optic nerve head measured by Laser Speckle Flowgraphy

Klemens Fondi  1 , Ahmed M Bata  1 , Nikolaus Luft  2   3 , Katarzyna J Witkowska  1 , René M Werkmeister  4 , Doreen Schmidl  1 , Matthias Bolz  2 , Leopold Schmetterer  1   4   5   6   7 , Gerhard Garhöfer  1
Affiliations
Clinical Trial

Evaluation of flicker induced hyperemia in the retina and optic nerve head measured by Laser Speckle Flowgraphy

Klemens Fondi et al. PLoS One. .

Abstract

Purpose: The coupling between neural activity and blood flow is a physiological key principle of ocular blood flow regulation. The current study was performed to investigate whether Laser speckle flowgraphy (LSFG), a commercially available technique for measuring blood flow, is capable to assess flicker-induced haemodynamic changes in the retinal and optic nerve head (ONH) circulation.

Methods: Twenty healthy subjects were included in this cross sectional study. A commercial LSFG instrument was used to measure blood flow at the ONH as well as in retinal vessels before and during stimulation with flickering light. Mean blur rate (MBR), a measure of relative blood flow velocity, was obtained for the ONH and relative flow volume (RFV) a measure of relative blood flow of the respective retinal vessels.

Results: Stimulation with flicker light increased ONH MBR by +17.5%±6.6% (p<0.01). In retinal arteries, flicker stimulation led an increase of +23.8±10.0% (p<0.05) in total RFV. For retinal veins, an increase of +23.1%±11.0 (p<0.05) in total RFV was observed during stimulation. A higher response was observed in nasal RFV compared to temporal RFV in retinal arteries (nasal: +28.9%±20.0%; temporal: +20.4%±17.6%, p<0.05) and veins (nasal: +28.3%±19.6%; temporal +17.8%±18.9%, p<0.05).

Conclusion: As shown previously with other techniques, flicker stimulation leads to an increase in retinal and optic nerve head blood flow. Our results indicate that LSFG is an appropriate method for the quantification of retinal and ONH blood flow during visual stimulation and may be used as a non-invasive, easy to use tool to assess neuro-vascular coupling in humans.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1
LSFG composite map with regions of interest (ROI) around the optic nerve head (a) and marking all nasal vessels (b). The corresponding flow diagram depicting MBR over recorded frame is shown on the right side of the figure.
Fig 2
Fig 2
In vitro experiment: The relationship between preset velocity rates in the glascapillary and LSFG measurements in the present (black circles) and absence (open circles) of flicker stimulation (left panels). Right panels show the linear correlation between LSFG measurements in presence and absence of flicker stimulation.
Fig 3
Fig 3. The correlation between flicker induced hyperemia in retinal arteries and retinal veins expressed as percent change over baseline (n = 20, p<0.05).
See this image and copyright information in PMC

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