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Preventing mask interference with visual field testing during the COVID-19 pandemic


Dealing with the COVID-19 virus affects everything to some degree, and investigators have found that mask wear can impact the accuracy of visual field tests.

Dealing with the coronavirus disease 2019 (COVID-19) virus affects everything to some degree, and artefacts related to mask wear can impact the accuracy of visual field (VF) tests.

Masks that fit poorly can indicate that VF deterioration has progressed when that may not be the case. While wearing a mask is among the most effective ways to prevent viral spread, the challenge is to wear them correctly.

Investigators from the Department of Ophthalmology at Ramon y Cajal University Hospital in Madrid, and the Facultad Medicina, Universidad Alcalá, Alcalá de Henares, Spain, reported the incidence of false progression of VF

damage and suggested a practical approach to overcome it.1 Based on the VF testing, in many patients, the VF scotomas seemed to progress, even though the glaucoma seemed stable.

The team of investigators, led by Marta Gomez Mariscal, MD, cited a study that reported that face masks worn during VF testing can cause fogging of the trial lens inferiorly.2 The investigators also explained that patients find the masks to be distracting, uncomfortable, and claim shortness of breath, all of which may also contribute to erroneous results.

The investigators conducted a study between July and August 2020 that included 307 VF tests during which the patients wore FPP2/KN95 or surgical masks; these tests then were compared with tests carried out before the onset of the pandemic. When erroneous results were suspected, the tests were repeated and patients wore a surgical mask. The superior edge of the mask was held in place by adhesive tape to prevent the edge of the mask from being diagnosed as VF loss, they explained.


A total of 18 (5.8%) VFs were identified with a suspected progression artefact due to the masks. When the superior edge of the mask was taped down, in all cases, the median VF index and mean defect improved significantly and did not differ significantly from the tests performed the onset of the virus.

Among the affected tests, the inferior hemifield was affected more, followed by the central area, with either a new or enlarged scotoma seen.

The investigators suggested that patients wear a a surgical face mask with the superior border taped down to reduce the presence of these artefacts.


Gómez Mariscal M, Muñoz-Negrete FJ, Muñoz-Ramón PV, et al. Avoiding mask-related artefacts in visual field tests during the COVID-19 pandemic. Br J Ophthalmol 2021;0:1–5. doi:10.1136/bjophthalmol-2020-318408

Young SL, Smith ML, Tatham AJ. Visual field artifacts from face mask use. J Glaucoma 2020;29:989–91.

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