Researchers the United Kingdom propose that face masks may lead to visual field artifacts that have the potential to mimic pathologic field defects, according to a small case study published in the Journal of Glaucoma.1 

Physicians reported the case of a 32-year-old woman who underwent standard automated perimetry with the 24-2 Swedish Interactive Threshold Algorithm (SITA) Fast test of the Humphrey Field Analyzer 3.1

Following the examination, the clinicians noted that her ear-loop surgical face mask had ridden up, and that small amounts of condensate had been left on the perimeter lens.The visual fields showed good reliability indices, but the readings in both eyes showed a marked reduction in sensitivity inferiorly, particularly worse in the left eye. The glaucoma hemifield test was outside normal limits in both the eyes.1


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When the patient was asked to adjust her mask, the re-examination showed resolution of the inferior sensitivity defects.1 The repositioning required her to pinch down the nose wire to ensure  that the upper border of the mask was well sealed.1 The patient was also asked to secure the loops around her ears.1

With the COVID-19 pandemic still ongoing, masking protocols are mandatory for most establishments — including the ophthalmology clinic.1 Many patients are choosing homemade and nonmedical grade masks, which the study authors noted are “likely to lead to patients using a variety of face masks during perimetry, some of which may be more prone to causing artifact.” In particular, the authors pointed to additional research showing that “fluid-resistant surgical face masks with an ear-loop design can be more difficult to secure tightly enough to ensure a good seal compared with tie-back masks.2

Additionally, the clinicians suggested that most surgical masks are designed to fit the average male face, leaving female wearers with the potential for masks that are just oversized enough to allow for an air vent that can create artifacts on visual fields or cause other disruptions in an evaluation.1 Not only can masks physically obstruct ophthalmic testing, but some patients wearing masks during perimetry may also feel restricted and uncomfortable, potentially reducing test reliability, according to the clinicians.1

Poorly fitting face masks, perhaps disposable ones that are not designed for the patient wearing it or homemade ones, represent a new cause of visual field artifact.1 The researchers suggested that visual field technicians carefully advise patients on the need for a securely fastened face mask before visual field testing, and to monitor for any movement of the face mask during the test.1

“[T]his case highlights that there may be a greater need to monitor patients during testing if they are wearing a mask,” the clinicians reported. 

References

1 Young S, Smith M, Tatham A. Visual field artifacts from face mask use. J Glaucoma. 2020;29(10):989-991. doi:10.1097/IJG.0000000000001631

2. Public Health Scotland.Fluid-Resistant (Type IIR) Surgical Face Masks (FRSM). National Health Service. Published April 29, 2020. Accessed October 20, 2020. www.hps.scot.nhs.uk/web-resources-container/fluid-resistant-type-iir-surgical-face-masks-frsm/