Tear fluid soluble factors increased during face-mask-wearing era. Bar graphs represent the levels of cytokines—(a) IL-1α, (b) IL-1β, (c) IL-2, (d) IL-33, (e) IFNβ, (f) LIF, (g) TSLP; growth factors—(h) BDNF, (i) NGF; cytolytic protein—(j) perforin; and soluble receptors—(k) sTNFRI, (l) sIL-2R α in matched study subjects prior to and during the face-mask-wearing era. IL—interleukin; IFNβ—interferon beta; LIF—leukaemia inhibitory factor, an IL-6 class cytokine; TSLP—thymic stromal lymphopoietin; BDNF—brain-derived neurotrophic factor; NGF—nerve growth factor; sTNFRI—soluble tumour necrosis factor receptor I; sIL-2Rα—soluble form of IL-2 receptor alpha. N = 17; 34 eyes. Pre-FM indicates period where the study subjects were not wearing a face mask (pre COVID-19 era) for an extended period of time. Post-FM indicates the period where the same study subjects were wearing a face mask (during the COVID-19 pandemic) for an extended period of time (approximately 8 hours a day). Bar graph indicates mean ± SEM * p < 0.05, ** p < 0.01, *** p < 0.001; Wilcoxon matched-pairs signed rank test.