The use of eye protection to reduce the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is debatable. The World Health Organization (WHO) recommends eye protection like goggles or face shields to health care workers caring for coronavirus disease 2019 (COVID-19) patients. However, no such recommendation exists for those caring for COVID-19 patients at home, even when they live in the same room.
In the real world, the impact of eye protection on the control of SARS-CoV-2 infection is uncertain. Researchers from Australia recently conducted a systematic review of all available research studies on the impact of eye protection on the transmission of SARS-CoV-2.
Study: The effect of eye protection on SARS-CoV-2 transmission: a systematic review. Image Credit: Boyloso / Shutterstock.com
Criteria for extensive search including screening and data extraction
In their recent article published in the journal Antimicrobial Resistance and Infection Control, the authors explained the details of an extensive search they performed between January 1, 2020, and June 1, 2021, on the PROSPERO, Embase, PubMed, and Europe PMC for preprints databases, as well as the Cochrane Library for clinical studies. Additionally, the WHO International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov databases were also searched through June 1, 2021.
The criteria adopted by the authors for this systematic review were as follows: participants comprised community or health care workers; interventions included any eye protection such as face shields, goggles, or modified snorkel masks; comparators had no eye protection, with or without face masks; and the outcome was the number of lab-confirmed SARS-CoV-2 infection. All comparative studies, including before-and-after, were included, except those that did not provide sufficient data for comparison between with and without eye protection, laboratory experiments, and other eye equipment that was not meant for the prevention of respiratory viral transmission.
The studies were screened based on titles, abstracts, and full texts, as well as the risk of bias evaluated using the ROBINS-I for observational studies. The confounding factors identified for most of the studies included variation in risk of COVID-19 from before, during, and after the intervention, test frequency, comparator, and settings.
The authors screened 898 articles and included five published observational studies in six reports from four countries in the quantitative analysis. All five studies were conducted on healthcare workers who used eye protection ranging from wrap-around eyewear and goggles to full-face shields or visors in addition to approved masks and other infection preventive measures in the corresponding clinical setting.
The three before-and-after studies and one retrospective cohort study presented a statistically significant and considerable decrease in SARS-CoV-2 infections which favors eye protection with odds ratios ranging from 0.04 to 0.6, corresponding to risk reductions of 96% to 40%. Furthermore, in one case-control study, the reported odds ratio did not favor any eye protection, which might be due to an increase in community transmission.
Any significant meta-analysis was excluded due to the high heterogeneity between studies. Since none of the studies were adjusted for prospective confounders, the risk of bias increased and the certainty of the evidence decreased.
“These studies provide suggestive evidence that face shields provide some protective effect, and that this may be substantial.”
A previous study that reviewed observational studies on the impact of eye protection on SARS-CoV-1 and the Middle East respiratory syndrome (MERS) epidemics showed a decrease in transmission of 66% and 76%, respectively. This outcome is comparable with the reductions seen in the three before-after studies of this review.
Another study on mannikins also proved that face shields provide greater protection than masks. Since these studies did not include viral particles, the simulations of human interactions were incomplete.
Although these studies showed potential protection from face shields as an add-on to face masks, they did not clarify whether the protection is from reduced inhalation or eye protection. The present systematic review suggests that transmission of SARS-CoV-2 in healthcare workers may be reduced by using eye protection. However, further studies are needed to assess the effect of face shields that are used instead of or as add-ons to face masks, as well as to compare eye goggles and face shields with face masks.
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