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Optics Letters

Optics Letters


  • Editor: Xi-Cheng Zhang
  • Vol. 39, Iss. 3 — Feb. 1, 2014
  • pp: 610–613

Analysis of contrast and motion signals generated by human blood constituents in capillary flow

Phillip Bedggood and Andrew Metha  »View Author Affiliations

Optics Letters, Vol. 39, Issue 3, pp. 610-613 (2014)

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The flow of individual corpuscles through retinal capillaries may now be observed noninvasively by using adaptive optics (AO). To explore their imaging properties, we imaged retinal capillary flow in two healthy subjects at 593 nm with a flood-based AO ophthalmoscope, at a variety of retinal locations and levels of defocus. The image intensity of red cells and plasma depends upon capillary depth relative to focus: red cells appear brighter than background, and plasma darker, for capillaries posterior to focus. The reverse is true for capillaries anterior to focus. Contrast reversals were obtained over 0.05 D (14μm), which are well within the typical undulations in depth of retinal capillaries. We relate these observations to phase-contrast defocusing microscopy. This defocusing effect confounds flow measurements, which rely on correlation of image intensity between successive locations along the same capillary, a requirement made further difficult by high physiological variability in flow. Peak correlation was maintained >0.25 over a distance of 22±15μm (roughly the spacing between red cells) and over a duration of 154±49ms (roughly eight times the temporal period between red cells). We provide a 2D correlogram approach that significantly improves robustness in the face of optical and physiological variability, compared to the traditional spatiotemporal plot, without requiring additional data.

© 2014 Optical Society of America

OCIS Codes
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(170.1470) Medical optics and biotechnology : Blood or tissue constituent monitoring
(170.3880) Medical optics and biotechnology : Medical and biological imaging
(330.4875) Vision, color, and visual optics : Optics of physiological systems

ToC Category:
Medical Optics and Biotechnology

Original Manuscript: October 1, 2013
Revised Manuscript: December 12, 2013
Manuscript Accepted: December 23, 2013
Published: January 28, 2014

Virtual Issues
Vol. 9, Iss. 4 Virtual Journal for Biomedical Optics
March 27, 2014 Spotlight on Optics

Phillip Bedggood and Andrew Metha, "Analysis of contrast and motion signals generated by human blood constituents in capillary flow," Opt. Lett. 39, 610-613 (2014)

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