Eye discomfort due to dryness is one of the major complaints reported in indoor spaces. The purpose of this study was to quantitatively evaluate the effect of low humidity on eye discomfort in soft contact lens (SCL) and non-CL wearers. In addition to subjective sensations, physiological parameters related to eye discomfort including tear-film parameters and blink patterns were comparatively evaluated between relative humidities of 10% and 45% at 23°C. For both the SCL and non-CL wearer groups, low humidity had a significant effect on some of the measured physiological parameters. The SCL group showed lower ocular surface temperature and larger temperature differential after blinking at 10% relative humidity (RH) than that at 45% RH, indicating faster tear evaporation. Furthermore, their tear films tended to be thinner and have a shorter break-up time at 10% RH than at 45% RH. The non-CL group showed a significantly higher blink frequency and longer eye-closure time at 10% RH than at 45% RH, presumably as a compensatory response to the disturbance of the tear film due to low humidity. These results suggest the importance of humidity control in indoor spaces in terms of tear-film quality, which contributes to eye discomfort.

Eye discomfort is a major complaint reported in indoor spaces and has been suggested to be exacerbated by environmental conditions such as low humidity and high air velocity. Wearing face masks, which has become essential in our daily lives during the COVID-19 pandemic, can also cause eye discomfort by affecting the microclimate around the eyes. We conducted a pilot study to evaluate the effect of wearing masks on eye discomfort by measuring the physical environment around the eyes and short-term physiological and psychological responses and comparing them with and without surgical face masks. The results showed that when the participant wore a mask, exhaled air flowed out through the gap at the top edge of the mask, resulting in a higher air velocity and absolute humidity around the eyes than when the mask was not worn. No significant differences were found in subjective discomfort, tear-film stability, ocular surface temperature or blink frequency. However, the tear evaporation rate, estimated based on physical measurements, was greater when wearing a mask than when not wearing it. This study revealed that wearing face masks can negatively affect the environment around the eyes in terms of tear-film health.