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Title

Face masks: a new factor causing visual field artefacts

Purpose	During the current pandemic, face masks are routinely used in the outpatient clinics to prevent further spreading of SARS-CoV-2. The need to be aware of improperly fitted face masks as a cause of artefacts on automated perimetry possibly mimicking pathological field defects is described.
Methods	Two patients with chronic open-angle glaucoma underwent automated visual field testing with and without the use of a face mask.
Results	A 68-year old lady in follow-up because of familial glaucoma risk developed a new temporal arcuate scotoma in the left eye on an automated central 30° visual field test in the absence of anatomical changes as measured with OCT of the nerve fiber layer or ganglion cell complex or previous IOP fluctuations. A 49-year old man, with a diagnosis of normal tension glaucoma, demonstrated a novel inferior arcuate scotoma in the right eye, again without any impact on the optic nerve or IOP. Although the rapid deterioration of visual fields raised a suspicion of an artefact in both patients, reliability indices were remarkably normal. The face mask was noted to cause fogging of the perimeter lens or refractive error correction. As such, the supposed progression disappeared rapidly with a retest without the face mask.
Conclusion	Face masks can cause a visual field artifact possibly mimicking pathological field defects. In case of atypical glaucomatous visual field progression or progression not matched by findings on OCT, even with normal reliability indices, the wearing of a face mask must be considered as a factor causing an artefact.
Conflict of interest	No

Authors 1

Last name	VERMORGEN
Initials	K
Department	Department of Ophthalmology, Glaucoma,
City	Ghent University Hospital

Authors 2

Last name	De Zaeytijd
Initials	J
Department	Department of Ophthalmology, Medical Retina
City	Ghent University Hospital