Consensus recommendations on tear fluid terminology: A Delphi study by the tear research network

Purpose: Tear fluid is a clinically relevant body fluid frequently used in ocular disease and biomarker research. However, inconsistent terminology has limited data comparability and hindered clinical translation. This international Delphi consensus study, conducted by the Tear Research Network, aimed to establish standardized definitions for commonly used synonyms related to tear fluid. Methods: In two rounds of online surveys, 103 eligible professionals participated, primarily (clinical) researchers with broad international representation. Results: Consensus (>= 70% agreement or disagreement) was achieved on definitions including localization, source and function, as well as the context of use and sample collection. A standardized glossary was developed, with the strongest agreement (>90%) for tear fluid and tear film. The term tear fluid best describes the body fluid itself and its collected sample, while tear film refers specifically to the multilayered structure on the ocular surface. Both terms are recommended for clinical and research use and to describe the fluid analysed in various diagnostic tests. Conclusions: These recommendations support comparability, consistent reporting and interdisciplinary communication in future research.