Diurnal changes of noninvasive parameters of ocular surface in healthy subjects before and after continuous face mask wearing during the COVID-19 pandemic

To investigate whether diurnal changes in noninvasive ocular surface parameters and subjective symptoms occur in healthy subjects wearing face mask who were analyzed before and after 8 h of continuous use. In this prospective cross-sectional study, healthy volunteers attending the same workplace environment underwent a noninvasive ocular surface workup by means of Keratograph 5 M (Oculus, Wetzlar, Germany) in the same day at 2 different time points: (i) in the early morning before wearing face mask (T0); (ii) after 8 h of continuous face mask use (T1). Noninvasive break-up time (NIBUT), tear meniscus height (TMH), ocular redness and meibomian gland dropout were measured. All subjects were asked to complete the Ocular Surface Disease Index (OSDI) questionnaire before and after 8 h of face mask wearing. Data from 20 healthy subjects (10 males and 10 females, mean age 25.1 +/- 3.9 years) were included. Mean value of TMH decreased significantly from 0.29 +/- 0.07 at T0 to 0.23 +/- 0.07 mm at T1 (P < 0.001); conversely, mean values of NIBUT, redness score and meibomian gland dropout did not change significantly after continuous face mask wearing (always P > 0.532). Concerning ocular discomfort symptoms, mean value of OSDI score worsened significantly at T1 compared to T0 (from 12.9 +/- 12.6 to 19.4 +/- 12.0; P = 0.017). Continuous face mask wearing for 8 h led to decreased TMH associated with the onset of ocular discomfort symptoms in young healthy subjects.