And Some Good News: Patients’ Tears Don’t Carry Virus?

And Some Good News: Patients’ Tears Don’t Carry Virus?

Dear Colleagues,

A few days ago, I shared a post titled “From the Chairperson" on the TODNet forum. Quoting the American Academy of Ophthalmology (AAO), I wrote that the prevalence of conjunctivitis among COVID-19 patients was around 1% and that the virus was not spread by tears in the absence of conjunctivitis. At the same time, however, the AAO was advising ophthalmologists not to use air-puff tonometers in order to prevent spread via aerosols, because they cause tear splashing. If there is no virus in tears, then why was this precaution necessary?

It should be perceived as quite normal that the global medical community, which was caught unprepared for this pandemic and has very little experience with the COVID-19 virus, often descends into contradiction with such hypothetical approaches. Of course, we can expect that as evidence-based information becomes available, hypothetical approaches like in this example will gradually decrease.

The study to which I referred was conducted on COVID-19-positive patients in Singapore and reported by Rupesh Agrawal.¹ The source is, again, the AAO. I first read the article on Healio Ocular Surgery News. In this study, several samples were collected from 17 COVID-19-positive patients exhibiting the initial symptoms (generally within the first 20 days of the disease) with Schirmer's test strips between 3 and 20 days after symptom onset. None of the patients had ocular symptoms with the exception of one patient who developed conjunctivitis and chemosis. In total, 64 samples were collected (12 samples in the first week, 28 in the second week, and 24 in the third week after symptom onset). Reverse transcription polymerase chain reaction (RT-PCR) tests of nasal and pharyngeal samples were positive, while all tear samples tested negative.

The study was accepted for publication in the journal Ophthalmology on March 21, 2020 with Ivan Seah Yu Jun now listed as first author (submitted on March 19, 2020; (https://www.aaojournal.org/article/S0161-6420(20)30311-0/pdf).¹

Reading the discussion section of the article, one finds no notable physiopathological mechanism that explains these results. It only states that it is unknown whether the ACE2 receptor, to which SARS-CoV-2 binds to infect cells, is found in corneal and conjunctival cells.

To date, three routes of entry into the body have been reported for the virus: the mouth, nose, and eyes. Therefore, the eye is an important portal of entry. Only when and if this study is corroborated by other more extensive studies can it be concluded that the eye or tears are not a source of transmission. This would of course be good news for our colleagues, who perform ophthalmic examinations every day and are at risk of contact with tear secretions during slit-lamp examination.

In my opinion, the question of why a virus found in the nasopharynx is unable to reach the tears is another subject of scientific curiosity that requires further research. Could the composition of tears be involved in this (antibodies, lysozyme, water content that would damage the envelope structure of the virus, pH level, etc.), or might the valve structure of the nasolacrimal system prevent upstream flow? These questions will surely be answered before long.

I wanted to share this reassuring (even if only somewhat) information with you. Nevertheless, let us continue to exercise caution until the early evidence is confirmed with more extensive studies.

Best regards,

Compiled and Prepared by: Prof. Dr. İzzet Can

References:

^{1. Ivan Seah Yu Jun, MBBS, Danielle E. Anderson, PhD, Adrian Eng Zheng Kang, BSc, Lin-Fa Wang, PhD, Pooja Rao, MBBS, Barnaby Edward Young, MB, BChir, David Chien Lye, MBBS, Rupesh Agrawal, MD. Assessing Viral Shedding and Infectivity of Tears in Coronavirus Disease 2019 (COVID-19) Patients}