We already know that the SARS-CoV-2 coronavirus, which causes COVID-19, is spread through the mucous membranes (organic tissue that lines the organs that are outside the body); These mucous membranes include not only the nose and mouth, but also the eyes. While it is true that safety glasses to isolate the eyes, in addition to other accessories (such as a ‘hood’ that covers the ears) are part of the usual uniform of health workers, the official recommendations of governments and health authorities do not mention to eye protection for the general population, who, in Spain, have only imposed the mandatory use of masks in public places as long as an interpersonal distance of one meter cannot be guaranteed. Therefore, those systems that isolate the upper area of the face, which the masks reveal, would be ruled out: from glasses to the famous screens.
According to the Center for Disease Control and Prevention (CDC), the widespread use of eye protection, among other stricter prevention measures, among healthcare personnel is necessary because in hospitals there is repeated close contact with several different patients. On the other hand, among the general population (who should now wear masks, preferably reusable surgical or hygienic masks approved with the UNE0065 standard), there is no need to use generalized eye protection.
However, screens (basically, a transparent plastic barrier that covers the face) are beginning to become popular, especially among hoteliers, who in Spain have reopened their establishments (with restrictions) from phase 1 of the de-escalation . But are screens really effective? Why do some professionals advise against them?
Advantages of protective screens
An article published on April 29 in the Journal of the American Medical Association (JAMA) reviews screens and their effectiveness against SARS-CoV-2. The article recognizes a number of advantages of screen-type face shields, but with some restrictions. For example, among the advantages we find that face shields can be reused indefinitely and can be easily cleaned with soap and water , or common household disinfectants; while masks have limited durability and little potential for reuse. In addition, they prevent the user from touching their face; and, on the other hand, they give rise to the visibility of facial expressions and lip movements for the perception of speech, something that masks do not allow.
Finally, face shields do not require special manufacturing materials , as does the case with masks. Thus, numerous companies, including Apple, Nike, GM and John Deere, have begun to produce face shields.
A big drawback
But the main drawback is that screens can never be the only prevention resource. Marián (Boticaria) García, doctor in Pharmacy, disseminator and professor at the Isabel I University, believes that they should never be used ‘alone’, without the additional protection of the mask: “ the screens are, if anything, a complement, but not a substitute. They should never be used alone because when you sneeze, the secretions do not get trapped, but rather escape from the bottom ”.
In this sense, the JAMA article includes a guide to the effective use of protective screens: “For optimal protection, the screen should extend under the chin anteriorly, towards the ears laterally, and there should be no exposed space between the forehead and helmet of the protector ”.
For its part, The Lancet magazine published a meta-analysis on June 1 in which it examines physical distancing, masks and eye protection to prevent the spread of COVID-19. The researchers’ conclusion was that social distancing is the most effective measure to prevent coronavirus, while “any protective covering for the eyes or face is just an additional layer of protection, but not the only one.”
The healthcare setting aside, the evidence that screen-type face shields are effective when worn individually is low. However, Linda Bauld, a professor of public health at the University of Edinburgh, commented on this study for the Science Media Center and noted the following: A combination of eye protection and face masks can be particularly important protection for some groups of especially exposed workers ”.
Therefore, protective screens yes or no?
We conclude that for health personnel, yes, accompanied by other protection measures. And for the general population, it is not especially recommended. However, in highly exposed sectors, such as the hospitality industry, it can be a viable option as long as it is accompanied by a mask.
As for social distancing, there are doubts about whether the space to be respected between people should be one or two meters. On this, Bauld adds: “There have been many complaints that the UK recommendation of two meters is excessive because it is more than in other countries. But this meta-analysis backs it up. Maintaining a distance of two meters is likely to reduce risk compared to the recommendations of a single meter. Therefore, where possible, this is the distance that employees should use as more locations and workplaces open in the future. This will be very difficult in some environments, but it is important, and we will all have to get used to maintaining this distance for a few months. “
What can be extracted from both the JAMA and The Lancet studies and the comments of the experts, the prevention measures would be ordered, according to effectiveness, as follows:
- Social distancing of one meter (but preferably two) for everyone, regardless of additional protective measures.
- Masks (surgical or hygienic for the general population and FFP2 or N95 for people with symptoms, vulnerable, or who have tested positive for SARS-CoV-2.
- Screens, glasses or eye protection: optional and complementary, that is, always accompanied by a mask (never alone).
For his part, according to Dr. Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, also for Science Media Center: “Public health messages should be based on the best available evidence at the time that provides the greatest benefit for the majority. of people and easy to understand and follow. Simple messages, like washing hands and staying home, have been successful because they are easy to follow and they work. “
