Over the last decade, various techniques have been reported toimage microvascular networks, whose aims range from distinctresearch questions to the diagnosis and monitoring of specificpathologies. Color fundus photography, fluorescein angiography (FA), and indocyanine green angiography served asstandard methods for imaging the retinal vascular structure.1These imaging techniques require the injection of exogenouscontrast agents into the circulation, which may cause allergicreaction. Moreover, these techniques cannot provide blood vessel depth information and are limited by the two-dimensional(2-D) nature of the images.An attractive optical technique for imaging three-dimensional (3-D) microvasculature structure without the need ofexogenous agents is vascular-sensitive optical coherence tomography (OCT). The OCT technique is based on the principle oflow-coherence interferometry, and it offers the advantages ofbeing noninvasive, contactless, and yields depth-resolved localization at high spatial and temporal resolutions cross-sectionalimaging in biological systems.cross-sectional imaging in biological system.2,3 Moreover, intrinsic contrast mechanisms anddepth resolution of tissue are advantages over confocal fluorescence microscopy. Unlike the sound echoes of ultrasound, OCTgenerates images based upon back-reflected light from the sample. Various OCT blood flow detection techniques have beendeveloped for imaging vasculature structure, each of which hasits own merits and drawbacks. For example, Doppler OCT4–15(also known as optical Doppler tomography), images are reconstructed based on phase changes or Doppler frequency shifts dueto moving particles in the sample. Phase changes are calculatedfrom multiple axial scans (A-scans) collected at the same position, or adjacent A-scans with sufficient spatial overlap. TheDOCT method is useful in mapping blood vessels in varioustissue such as skin16,17 and retina18 and can extract bloodflow information. Several useful strategies such as dual-beamDOCT19–21 and narrow bandwidth phase-reference OCT,22 arereported to improve the sensitivity of DOCT. All of these methods are phase-sensitive, and therefore a phase-stable system isnecessary for obtaining high-contrast images.23The power Doppler OCT and/or optical angiography/microangiography (OMAG) are other imaging techniques based on theDoppler effect that is able to isolate blood flow signals from thestatic tissue background.24–36 This method does not allow visualization of flow velocity directly; it provides a measure of thetotal backscattered optical signal attributable to moving targetswith higher SNR37 compared to DOCT. Unlike phase-basedapproaches, OMAG directly analyzes and processes an image,which can minimize the phase instability noise. Different phasecompensation methods37–39 were introduced to compensatemotion artifacts from OMAG measurement. Overall real-timeapplication of power Doppler or OMAG is computationallyintensive and may require graphics processing unit (GPU)-based signal processing techniques to clinical suitability.Two recently developed high-contrast in vivo 2-D/3-D microcirculation imaging techniques, with various implementations