Lipid layer thickness
When no mask was worn, lipid layer thickness (LLT) was 64.79 nm in the healthy group and 81.02 in the DED group (Bland–Altman diagrams of lipid layer thickness (LLT) measurements. Each dot represents the average of two LLT measurements (in nm, Mean difference of measurements, In the DED group, LLT also showed no significant differences in the three different test situations (Table TOST of lipid layer thickness (LLT) measurements. The black square shows the mean difference of the two compared LLT measurements. The horizontal line shows the 96.8% confidence interval. The dashed vertical lines show the equivalence limits. Panels 