Methods
redness
In a prospective study, the tear film parameters of 42 DED patients and 42 healthy volunteers were examined while wearing different types of face masks in a randomized order. This included measurements of non-invasive tear break-up time (NIBUT), lipid layer thickness, tear meniscus height, and bulbar redness after 30 min of wearing no mask, a surgical face mask or an FFP2/K95 mask. The equivalence of the means was assessed using the two one-sided 