Editorial on the Research Topic Functional assessments of the ocular circulationIn recent years, ocular vascular functional imaging has gained importance due to the increasing availability of new methods such as optical coherence tomography angiography (OCTA) or Doppler OCT (DOCT). In contrast to static (morphological) imaging, functional imaging has the advantage that it provides insight into physiological and pathophysiological processes, which may greatly benefit the diagnosis, monitoring, and treatment of ocular diseases associated with vascular dysfunction. In addition, functional parameters are usually quantitative, which also makes them attractive as potential endpoints in clinical studies (1).Changes in ocular vascular parameters have also been shown to be associated with changes in the cerebral vasculature and therefore might have a great potential to become biomarkers for cerebrovascular diseases in the future (2, 3). Studies also found that retinal vascular parameters can assist in cardiovascular risk assessment (4).The technologies and methodologies for functional assessment of the ocular vasculature (i.e., vessel diameter, blood flow, branching angles, vessel density/tortuosity; as well as their dynamic changes) allow for direct observation of the retinal and intra-retinal vascular beds at rest but also when challenged. Flicker light provocation, cold exposure, inhalation of gas mixtures, exercise, and others are only few interventions that have been employed to study the functional aspects of the retinal circulation. All of those have advanced our understanding of physiological processes, but also of alterations due to systemic and local disease processes and aging.This issue entitled "Functional assessments of the ocular circulation" will provide an insight into methodological, technical, analytical, and clinical aspects of ocular imaging techniques and their potential in assessing steady-state and functional aspects of ocular and systemic disease. While the analyses of "big data" and the utilization of "artificial intelligence" has already seen a sharp increase in the implementation of retinal vascular parameters in such analyses (5, 6), it is still important to keep an eye on technical and methodological factors which can impact retinal vascular parameterisation prior to their use in further processing such as realized by artificial intelligence.