IDENTIFY infections that escape swabs with a test for Sars-CoV-2 conducted on tears. This is what they did at the University of Insubria in Varese by conducting a study that was published in Jama Ophthalmology. Researchers suspect that infected tears may be an additional route of transmission for Covid-19, a hypothesis that has been debated, but not clearly demonstrated.
Research
Between April and May 2020, researchers collected tear samples from both eyes of 108 patients, 91 of whom had received a diagnosis of Covid-19 and were hospitalized at three Intensive Care Units (ICUs) in northern Lombardy, the epicenter of the first European outbreak. The other 17 were healthy volunteers enrolled as a control group. In total, the virus was detected on the ocular surface in 52 of 91 patients. “The main purpose of the study was to investigate the presence of the Sars-CoV-2 virus in the eye, as the virus was found in numerous organs. and systems as well as in the lungs ”, explains Claudio Azzolini, professor of Ophthalmology at the University of Insubria in Varese ????. “We took the tear secretion from the bed of Covid patients with special sponges and with a delicate standard technique. The secretion was tested for the virus with highly specific molecular tests. Viral material was found in more than half of the patients studied. The virus has also been found in the eyes in some patients with overt disease but with a negative nose-pharyngeal test “.
The results
The main findings of the study refer to a subgroup of 41 Covid-19 patients, who the researchers were able to double-screen, with nasopharyngeal and conjunctival swabs, less than 48 hours apart. In this way, significant changes in viral load between tests could be ruled out, a factor that would otherwise skew the results. Of those 41 patients, 17 were found negative for nasopharyngeal swab despite their Covid-19 diagnosis. However, when the researchers took a second swab from both eyes, 10 of them tested positive.
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Spot false negatives
These results could prove useful in detecting infections that escape tampons. “Re-checking the result of the nasopharyngeal molecular tests with a second eye swab can reduce the rate of false negatives,” says Claudio Azzolini who led the study. “This suggests that performing an additional molecular test in the eyes of those who are negative for nose and pharynx swabs can reverse that initial result, revealing that the virus is actually in tears.” As for the 24 patients with positive nasal swab, 15 of them (63%) also obtained a positive result on the eye test. In the control group, all tests were negative.
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How Sars-CoV-2 moves
The authors believe that the most likely explanation for the appearance of the virus in the eye is that Sars-CoV-2 could travel on atmospheric particulate matter and remain in the atmosphere for hours or days, especially in a non-windy and polluted area, such as the plains. Lombard Po Valley. Once infected with the particulate matter, the tears would travel to the throat, potentially infecting both the upper and lower respiratory systems. “The virus hardly reaches the conjunctiva from the internal parts of the body. It probably also settles on the conjunctiva through atmospheric particulate matter. In fact, there was an increase in the number of infections two weeks after an increase in the level of air contamination, the time interval between infection and disease ”, explains Azzolini. “Since the tear flow secreted by the lacrimal glands reaches the anterior eye and then through the lacrimal dots (small orifices that from the eyelids near the nose) reaches the throat, it is hypothesized that it also reaches the lungs.” Tears can therefore be a gateway to the disease. “The clinical case of the Wuhan ophthalmologist, Li Wenliang”, the doctor-hero among the first to lose his life in China, “can be an example of this spread. The results support the use of eye protection for people working in environments where ocular infection is possible ”.
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The reliability of eye swabs
The possible role of tears in coronavirus transmission is still debated, as is the actual effectiveness of eye swabs even though the results of previous studies may have been influenced by the different skill levels of the staff performing the eye swabs, as well as experience. individual laboratory diagnostics. “It is no coincidence that we wanted only one ophthalmologist to perform swabs, with a specific procedure, in all patients and volunteers of the study, in order to avoid that any distortions in the results could depend not on the test itself, but on the greater or less skill of different hands involved in the procedure, “explains Azzolini. Thanks to this procedure, Insubria researchers are the first to have found the virus in the eyes of so many patients.
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Protective glasses and eye pads
These results can have a very practical impact in the immediate term by suggesting actions that can promote early diagnosis and prevention. “Since we have found the presence of the virus on the conjunctival swab even in patients with negative nasopharyngeal swab – Azzolini points out – the use of conjunctival swabs could be considered as an aid for early diagnosis. Furthermore, in the light of these results, protective goggles could be useful in risky environments, for example, in very crowded places, where there is little air exchange or where there are people with colds and sneezing ”. And then we have to understand what consequences the presence of the virus has in the eyes at the ocular level: “Since we do not know the long-term effects of Sars-CoV-2 in various organs and systems, not only in the eyes, we are ending to build on the ‘Eumeda’ medical computer platform, an electronic medical record with information on many organs and body systems of sick patients, to see over time, after months or years, any changes to the various organs “.
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