Microcirculation plays an essential role in the interaction between the blood and target tissues. Despite its evident importance in the pathophysiology and development of numerous acute and chronic diseases such as hypertension, diabetes or sepsis, currently available methods allowing direct visualization of the microcirculatory network and its assessment in clinical practice are very limited. Orthogonal polarization spectral (OPS) imaging and its improved successor Sidestream dark-field (SDF) imaging are relatively new optical non-invasive technologies incorporated in a hand-held examination probe for visualization of the mucosal surface microcirculation including the human sublingual area. The basic principles of these methods, an appraisal of the validation studies, the current options of experimental and clinical applications and the advantages and technical limitations of the methods are discussed in this review

        Key words: microcirculation – orthogonal polarization spectral (OPS) imaging – sidestream dark-field (SDF) imaging