  Introduction. The aim is to provide a summary of methods available for the
assessment of tear turnover and tear clearance rates. The review defines tear
clearance and tear turnover and describes their implication for ocular surface
health. Additionally, it describes main types of techniques for measuring tear
turnover, including fluorescein tear clearance tests, techniques utilizing
electromagnetic spectrum and tracer molecule and novel experimental techniques
utilizing optical coherence tomography and fluorescein profilometry. Areas
covered. Internet databases (PubMed, Science Direct, Google Scholar) and most
frequently cited references were used as a principal resource of information on
tear turnover rate and tear clearance rate, presenting methodologies and
equipment, as well as their definition and implications for the anterior eye
surface health and function. Keywords used for data-search were as follows:
tear turnover, tear clearance, fluorescein clearance, scintigraphy,
fluorophotometry, tear flow, drainage, tear meniscus dynamics, Krehbiel flow
and lacrimal functional unit. Expert Commentary. After decades, the topic of
tear turnover assessment is reintroduced. Recently, new techniques have been
developed to propose less invasive, less time consuming and simpler
methodologies for the assessment of tear dynamics that have the potential to be
utilized in a clinical practice. Keywords. Fluorescein clearance test,
fluorophotometry, tear clearance, tear film dynamics, tear turnover,
scintigraphy, optical coherence tomography.
