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    Mask-Related Artifacts

    Personal protective measures, including universal masking in response to COVID-19, are nec­essary precautions that reduce the transmission rate of the virus.1 Because universal masking of patients is a relatively new prac­tice in the ophthalmology clinic,2 the practitioner must become aware of how face masks can influence patients’ assessment and management. In “Watch for Mask-Related Diagnostic Artifacts” (Letters, July), Drs. Palmer and Volpe reported how mask-induced condensation on the perimeter lens resulted in a visual field artifact that can be avoided by taping the mask.

    We have made two observations: First, commonly worn protective masks tend to obscure the lower portion of the wearer’s visual field. We therefore hypothesized that a mask could induce an inferior nasal artifact. Additionally, after an incident in which a face mask interfered with Goldmann applanation tonometry, we imagined a mask could induce a ring artifact by disallowing proper trial lens placement.

    We attempted to create both the inferior nasal step and ring artifact in a worst-case scenario demonstration and were unable to create the inferior nasal step. When we used cloth masks, surgical masks, activated carbon filtering masks, and KN95s, no mask intruded on the central 30 degrees tested by the perimeter. While the test subject wore a KN95 mask, a ring artifact occurred when the technician stopped advanc­ing the trial lens before it touched the bulky mask. This artifact can be easily obviated by allowing the trial lens bar to depress the mask if necessary. In this case, care must be taken to clean the trial lens holder after the exam. As is noted in the letter by Drs. Palmer and Volpe, the size of the patient’s mask may interfere with other diagnostic tests. We recom­mend that when this is the case the patient be provided with a surgical or cloth mask.

    Note that we did not have access to 3M 1860 surgical masks. In the absence of counterexamples, this demonstra­tion may ensure the validity of inferior nasal steps observed in visual field tests conducted with masks and may help to prevent ring artifacts.

    Grant Slagle, DO
    Mario Montelongo, MD
    William E. Sponsel, MD
    University of the Incarnate Word
    San Antonio

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    1 Brooks JT et al. JAMA. Published online July 14, 2020.

    2 Naveed H et al. Eye (Lond). 2020;34(7):1172-1174.