I never really thought about exhaled breath, except for the times that my own or someone else’s had an unpleasant odor, until practicing eye care in a time of active pandemic. Aligning with other large facilities and private practices across New York state and the nation, our offices are open to accommodate eyecare, medical, and dental emergencies only. Strict infection-control policies and practices for patients and providers are in place, including that both practitioners and patients are face-masked.

I have been irritatingly hampered by lens fogging precipitated by the use of the bi-directional mask barriers. On the patient side, spectacle-clad mask-wearing patient visual acuities can be errant, and phoropter lenses can become blurred. On the practitioner end, slit lamp oculars fog, and 90D/78D lenses become misted. The face mask directs much of the exhaled air upward, where it comes into contact with these lenses. The misting occurs from the warm water vapor in exhaled breath condensing on the cooler surface of the lenses, forming tiny droplets.

In Search of a Strategy

I have consulted medical-surgical, dental, photography, wood-working, motorcycle, and other websites as well as white papers, YouTube videos, and even domestic and foreign blogs to garner a remediation strategy for my lens-fog problem. The goal is to either coat lenses with an anti-fog preparation or limit the escape of exhaled air from the top of the mask.

Washing spectacles and diagnostic lenses with soapy water leaves behind a thin surfactant film that spreads water molecules evenly into a transparent layer (Malik and Malik, 2011). This is helpful for practitioner and patient spectacles and for diagnostic lenses (e.g., 78D/90D lenses) but cannot be used for phoropter lenses or slit lamp oculars.

We are left with defining breath/mask air flow strategies to limit exhaled breath from exiting the top of the mask. Here are a few options:

  1. For surgical masks (looser fitting masks, e.g., level 1 masks), tape the top of the mask over the bridge and malar area or purchase masks that have adhesive applied on the top inner side of the mask, creating a seal between the mask and face.
  2. Create side vents for exhaled breath to escape. This can be done by mask tying technique or ear loop twisting. Surgical masks are usually knotted so that the two ties lie nearly parallel above and below the ear. Alternatively, knot the superior tie first directly below the ear, then bring the inferior tie up in front of the ear and knot it over the crown of the head. This approach creates a closer seal over the nose and along the infraorbital ridge, which prevents venting at the superior part of the face mask and forms two lateral “vents” that allow exhaled air to exit (Jordan and Pritchard-Jones, 2014). For masks with elastic loops that wrap around the ears, twist the ear loops once to form a cross that pulls the sides of the mask, creating a small vent area. Another way is to form two lateral bends (near the edge of the outer eyebrows) in the wire that you form fit to the bridge of your nose.
  3. Place a folded tissue near the top of the mask to absorb the warm and moist exhaled air. Absorbent, quality tissue is recommended.
  4. Use masks that contour more closely to the face, either by design (e.g., N95 fit-tested masks) or material (stretchy materials such as neoprene) that also provide a barrier to prevent exhaled air from being released from the mask.

My favorite, yet clinically untested, solution for practitioners is a directional breathing technique employed by flute musicians (Yuko, 2020). With practice, examiners can direct exhaled breath downward to prevent its escape from the top of the face mask. As we cannot fully anticipate the duration of our pandemic remediation procedures and can foresee an increasing number of patients on our schedules while maintaining infection-control procedures such as wearing face masks, this select breathing skill may be one to cultivate for our months of practice ahead. CLS

For references, please visit and click on document #295.