Purpose: To propose and to evaluate a quantitative measuring method of meibomian gland (MG) vagueness. Methods: A total of 47 patients (32 female and 15 male, 39.21 AE 11.07 years) with meibomian gland dysfunction (MGD) were recruited to the MGD group, and 47 healthy volunteers were recruited to the control group matched in age and gender. The clinical examinations included ocular surface evaluation, MG function indexes and MG morphological indexes (including MG vagueness value). Reliability and efficacy of MG vagueness value, correlation between vagueness value and relevant variables, and diagnostic efficacy of combining vagueness value with efficacious indexes were all evaluated. Results: The MG vagueness value of the MGD group (19.78 AE 13.17) was significantly lower than that of the control group (31.90 AE 13.15). The vagueness value possessed good between-reader reliability (intraclass correlation coefficient = 0.928 > 0.9), and was correlated with age (r = À0.356), most clinical indexes and the acinar shortest diameter (r = À0.278). The area under the curve (AUC) in the receiver operating characteristic (ROC) curve of vagueness value was 0.766 [95% confidence interval (CI): 0.668-0.864] with sufficient diagnostic efficacy, and the cutoff value was <21. The AUC improved to 0.956 (95% CI: 0.938-0.999), after efficacious indexes (vagueness value, meiboscore and tear breakup time) were combined. Conclusion: Meibomian gland (MG) vagueness is quantifiable. The MG vagueness value proposed in this study has good reliability, a close relationship with MGD clinical features and sufficient diagnostic efficacy. Combining this new index with other indexes commonly used offers an exciting prospect in MGD diagnosis.