Since the beginning of the COVID-19 pandemic, face masks have become a part of people’s everyday lives when in public, including during exercise. Researchers decided to investigate whether mask wearing influences activities such as exercise and sought to determine the possible impact mask wearing has on retinal microvasculature.

In this study, 23 healthy young adults with different masks participated in a running test wherein speed was gradually increased until their heart rate reached 190 BPM. OCT angiography of the macula and optic nerve head were performed before and after the test to detect changes in retinal vessel density (VD). Participants were studied in three groups: volunteers without a mask, with a surgical mask and with an N95 mask.

Before exercise, the N95 group showed significantly reduced VD in the superficial plexus, except foveal VD, compared with unmasked subjects. After exercise, both masked groups showed significantly shorter maximum running time, lower oxygen saturation and lower perifoveal VD of SP compared with unmasked subjects.

The study concludes the use of an N95 mask reduced VD in the superficial plexus even under quiescent conditions, which might have clinical implications for protecting healthy workers and indoor manual labor workers from potential risks of retinal damage due to long-term mask use.

A notable finding was that, although only perifoveal VD in the superficial plexus showed significant reductions in mask-wearing groups after ICRT, heart rate reached 190 BPM significantly earlier and oxygen saturation was significantly lower upon completion of the exercise test during the use of surgical or N95 masks.

The authors found this notable because a previous study showed that surgical mask use significantly aggravated difficulty in breathing (dyspnea) during the six-minute walk test compared to the absence of a surgical mask during the test.

“Moreover, N95 and surgical masks might perform airflow restriction comparable to that of an elevation training mask, which has been used to simulate a hypoxic environment (similar to altitude training) for athletes,” the authors noted in their study. “Mask use has been shown to cause some adverse effects, including delayed cardiac-autonomic recovery from exercise, attenuated exercise ability, reduced awareness of sports injury, and hypoxemia. Our results indicate that the use of an N95 or surgical mask also might lead to a decline in exercise ability and earlier and stronger reductions of retinal VD in young adults.”

Because of this, the authors believe the public should use caution while exercising with a face mask, being mindful to take unmasked breaks when possible, and limit physical activities during mask wear.