Avoiding mask-related artefacts in visual field tests during the COVID-19 pandemic

Abstract

AimsTo assess visual field (VF) pseudoprogression related to face mask use.MethodsWe reviewed a total of 307 VFs performed with a face mask (FPP2/KN95 or surgical masks) and compared them with prior VFs, performed before the pandemic. VFs with suspected pseudoprogression due to mask artefacts (VF test 1) were repeated with a surgical mask and an adhesive tape on its superior border (VF test 2) to distinguish from true VF loss. Several parameters including reliability indices, test duration, VF index (VFI), mean defect (MD) and pattern deviation probability plots were compared among last pre-COVID VFs, VF tests 1 and VF tests 2, using the Wilcoxon signed-rank test.ResultsWe identified 18 VFs with suspected progression artefact due to masks (5.8%). In all of them, the median VFI and MD significantly improved after fitting the superior border of the mask, showing no significant differences with pre-COVID tests. The median fixation losses were significantly higher when wearing the unfitted mask (13% vs 6%,p=0.047). The inferior hemifield was the most affected, either as a new scotoma or as an enlargement of a prior defect.ConclusionUnfitted masks can simulate VF progression in around 6% of cases, mainly in the inferior hemifield, and increase significantly the rate of fixation losses. A similar rate of artefacts was observed using FPP2/KN95 or surgical masks. The use of a surgical mask with an adhesive tape covering the superior border may reduce mask-related artefacts, although concomitant progression cannot be ruled out in all cases.

OCT-Angiography Face Mask–Associated Artifacts During the COVID-19 Pandemic

“…30 As alluded to earlier, several studies have shown that fogging may result in unreliable VF testing and induced glaucoma-like artifacts because of obstructing patients' vision, which leads to inconsistent VF responses. [2][3][4][5] Alternatively, fogging may not increase the area of artifacts nor affect vessel density measurements in OCT-A imaging. This is probably because of differences with each technique; VF is a subjective measure of central and peripheral vision, whereas OCT-A is an objective measure of vessel density and does not depend on patients' responses.…”

Visual fields in glaucoma: Where are we now?

“…Mask artefacts can occur, especially in the inferior field, and have a significantly increased rate of fixation losses. 5 It is proposed the most likely reason for artefacts is the breath exhaled through the superior border of the mask, resulting in fogging of the perimeter's trial lens. This can be reduced with adhesive tape covering the superior border of the mask.…”

“…It is proposed the most likely reason for artefacts is the breath exhaled through the superior border of the mask, resulting in fogging of the perimeter's trial lens. This can be reduced with adhesive tape covering the superior border of the mask 5 . It is also important to note real progression of the field due to glaucoma is not dismissed as a mask artefact and that a repeat field in combination with OCT of the nerve fibre and ganglion cell layers be performed.…”

“…Patients can be asked to wear masks; however proper fitting of the mask is needed to ensure an adequate seal. Mask artefacts can occur, especially in the inferior field, and have a significantly increased rate of fixation losses 5 . It is proposed the most likely reason for artefacts is the breath exhaled through the superior border of the mask, resulting in fogging of the perimeter's trial lens.…”

The curious cases of incorrect face mask positions in bowl-type perimetry versus enclosed chamber perimetry during the COVID-19 pandemic

“…Periodical awareness and constant reinforcements can prevent both aerosol-mediated infections and mask-induced artifacts from bowl-type perimetry. [ 10 ] However, for the time being, it seems appropriate to use an enclosed chamber perimeter for assessing glaucoma patients, at least until the pandemic gets over, for erroneous mask wearers or for patients who have mask intolerance while performing visual fields.…”