Background/Objectives: This review considered meibomian gland functional assays, reported in recent dry eye treatment trials, that have potential as a clinical/physiological measure in a Core Outcome Set in dry eye clinical trials. The focus was on clinical methods that can be applied globally by trained clinicians. Methods: An electronic search of the MEDLINE database (via PubMed) was conducted to identify randomized controlled trials published in English between 1 January 1995 and 11 December 2025. The search strategy used the terms (meibomian OR meibography) AND treatment. Studies were included if they reported outcomes related to meibum secretion and/or meibomian gland expressibility in human participants. Moreover, a retrospective chart review was undertaken from previously unpublished meibum grading data to determine whether opacity and viscosity grades for meibum are correlated. Results: 98 studies were included for analysis The grading systems of Bron and co-workers, combined with that of the similar MGD Workshop report, were the most prevalent (n = 48), followed by Lane and co-workers (n = 23) and Shimazaki and co-workers (n = 10). Expressibility grading systems were most prevalent for Pflugfelder et al. (n = 33), followed by Blackie-Korb (n = 19) and Author defined (n = 17). The retrospective analysis of 69 charts suggests high correlation between meibum opacity and viscosity (Pearson’s r = 0.904, p < 0.001. 95% CI 0.849–0.940). Conclusions: Grading meibum quality is important in dry eye diagnosis and treatment. A modification of the MGD Workshop system appears useful as a core outcome set parameter in dry eye treatment trials.
Ansari et al. (Mon,) studied this question.