Assessing blood flow, as well as blood volume and oxygen saturation, is of utmost importance for health monitoring. Assessing microcirculation, as opposed to macrocirculation, is especially important for assessing the local tissue viability. Many optics-based modalities have been developed recently such as laser speckle contrast imaging (LSCI), laser Doppler flowmetry (LDF), diffuse correlation spectroscopy (DCS), and diffuse speckle contrast analysis (DSCA), which all share the advantage of non-invasive measurement of blood flow using non-ionizing radiation. This paper offers a review of these modalities centered around DSCA, which was developed most recently and is considered one of the fastest and most affordable deep tissue perfusion probes.