Researchers in China have found that people who wear glasses appear to be at a lower risk of contracting COVID-19.
The authors of the study, published in JAMA Ophthalmology, noted that since the coronavirus outbreak in Wuhan in December 2019, few patients with glasses have been hospitalized with COVID-19.
To investigate further, they collected data on eyeglass use from all COVID-19 patients as part of their medical history.
Their small study found that only 16 (5.8%) of the 276 admitted patients with COVID-19 wore glasses for more than eight hours a day.
When they determined that all of these patients were nearsighted, they later looked for the percentage of people with nearsightedness (myopia) in Hubei province, where the hospital is located.
They found that this is much larger (31
This is a fascinating observation, but as with all individual studies, the results must be treated with caution.
Although eye protection has always been an important component of personal protective equipment (PPE), the magnitude of the difference reported by this study raises suspicion.
This isn’t to say the results may not be real, but rather that we shouldn’t start recommending large-scale behavioral changes (like wearing glasses alongside our face masks) until they have been independently confirmed.
Are the eyes a window to the virus?
One of the key steps for any viral infection is the initial entry into the body. While most of our body is covered in protective skin, which is very effective in preventing viruses or bacteria from entering our body, much thinner “membranes” cover our airways, digestive system and eyes.
The role of these thinner membranes is to allow external things like oxygen, food and, in the case of the eyes, light, into our body. Unfortunately, viruses have learned to take advantage of these entry points.
This is why PPE is designed to protect these entry points, through the use of face masks, goggles and protective clothing.
However, while we might imagine that the main attack on these regions comes from viral particles transmitted through the air as aerosols, the main way the viral particles get to these weak spots is actually through our hands. Hence the COVID-19 advice to wash your hands often, for 20 seconds or more, and avoid touching our faces.
It therefore makes sense that covering your eyes with glasses can offer extra protection, both from the virus that can be carried in other people’s breath, but also in preventing the wearer from touching their eyes.
In fact, as early as February, there were reports of people catching COVID-19 not adequately protecting their eyes in health care facilities. It is also known that similar entry points (ACE-2 receptors) favored by the coronavirus are also present in the eyes.
Should we start wearing glasses?
A key part of interpreting any evidence from observational studies is remembering that correlation (two things happening together) doesn’t necessarily mean causation (one thing causes the other). To verify causation, a trial or controlled test is now required.
Ideally, this should follow two carefully matched groups of people – some with glasses and others without glasses – to see which group gets infected most often. The evidence from such a controlled study will always be much stronger than that of an observational study like the one in the recent article.
We should also note that the authors of this study listed a number of weaknesses. It was a very small studio on one site.
The researchers’ data for the general population came from a much earlier study of a sample that didn’t exactly match (in terms of age, demographics, and other factors) the sample admitted to hospital with COVID-19. And they couldn’t guarantee that all people with myopia in the general population also wore glasses for more than eight hours a day.
So while this new study is very interesting, there are many reasons to be cautious about this result. Certainly we need more data before we can give advice on using glasses together with our face masks.
Simon Kolstoe, Senior Lecturer in Evidence-Based Healthcare and University Ethics Advisor, University of Portsmouth.
This article was republished by The Conversation under a Creative Commons license. Read the original article.