Eye protection when used by healthcare workers either as face shields or goggles appears to reduce the incidence of COVID-19 infection
Using eye protection, either as goggles or a face shields seems to reduce the incidence of COVID-19 infection among healthcare workers. This is the finding of a systematic review by a team from the Institute for Evidence-Based Healthcare, Bond University, Australia.
Research during the pandemic has identified how the virus gains cellular entry via interaction with the angiotensin converting enzyme 2 (ACE2) receptor which is present on the surface of cells in the respiratory system. However, these receptors are also known to be present on the corneal and conjunctival surfaces and therefore this could serve as an entry portal for the virus. In fact, it was recognised as early as 1919, that the eye could be a route for the transmission of infections. Whether this was also true for COVID-19 is unclear but in a small study among Indian healthcare workers, it was found that no COVID-19 infections were recorded among community health workers after face shields were added to the list of required personal protective equipment. Furthermore, other, albeit, indirect evidence that COVID-19 could enter the body via the ocular route, came from a Chinese study, which found that the incidence of COVID-19 infection was less among those wearing glasses for more 8 hours per day.
For the present study, the Australian team set out to examine the potential contribution of eye protection towards the transmission of COVID-19. Searching the main databases (e.g., PubMed, Embase etc) the team looked for studies in which reported on the use of any form of eye protection, including face shields, goggles or modified snorkel masks, with or without face masks, comparative studies (i.e., without eye protection) and where the outcomes such as laboratory confirmed COVID-19 infection had been confirmed.
Findings
While identifying 898 articles, only 5 observational and therefore non-randomised studies were ultimately included in the analysis. This included three before and after studies, one case-control and one retrospective analysis. The limited data also precluded the use of a meta-analysis and since the studies did not adjust for potential confounders, there was a risk of bias designed as serious for two studies and moderate for the remaining three.
Eye protection used included face shields (three studies) and wraparound eyewear, goggles and full face shields or visors. From the three studies that reported before and after data, there was a statistically significant reduction in COVID-19 infections with the use of eye protection. For example, compared to no eye protection, the odds ratios (ORs) for a protective effect from the three studies ranged from 0.04 to 0.6, i.e., a reduction in risk from between 96% to 40%. In contrast, the single case controlled study suggested a reduced risk of infection among those not using eye protection.
The authors concluded that these studies provided suggestive evidence that face shields provide some protective effect but accepted that it was not possible to determine whether the protection against the virus arose from either reduced inhalation or ocular transmission.
Citation
Byambasuren O et al. The effect of eye protection on SARS-CoV-2 transmission: a systematic review Antimicrob Resist Infect Control 2021
