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Study: Low Risk Of COVID-19 Transmission Via Tears, Eyewear Is Still Important

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A new Ophthalmology study found no traces of SARS-CoV-2, the virus responsible for COVID-19, in 64 tear samples from 17 COVID-19 patients in Singapore, pointing to a low risk of viral spread through tears. Experts still implore caution and the use of protective eyewear, especially among practicing ophthalmologists, as larger studies investigating COVID-19 patients with ocular symptoms are still necessary.

Based on current evidence, SARS-CoV-2 spreads via respiratory droplets, such as coughing and sneezing, and through contact. Last month, two groups published pleas in the British Journal Of Ophthalmology and The Lancet, calling on frontline healthcare workers to not ignore the potential of transmission of SARS-CoV-2 via tears. This risk remains difficult to evaluate, in part because ocular symptoms are rare. Only nine (0.8%) of 1,099 COVID-19 patients in China had conjunctival ingestion, better known as pink or red eye.

In an email, Rupesh Agrawal, a senior consultant at the Tan Tock Seng Hospital, and Ivan Seah, an ophthalmology trainee at the National University Hospital, pointed out that there have been multiple reports which suggested the transmission of SARS-CoV-2 via ocular fluids. This includes a recent Journal of Medical Virology study, where out of 30 COVID-19 patients, only one had conjunctivitis and also tested positive for the virus in their tears.

“As ophthalmologists, we come into close contact with tears on a daily basis during our clinical examination […] We embarked on this study as we wanted to know if the virus can truly be found in tears,” said Agrawal and Seah, who are both based in Singapore.

In this study, Agrawal, Seah and their fellow researchers recruited 17 COVID-19 patients. Both nasopharyngeal swabs and tear samples were taken at various time points during the second and third week of COVID-19 symptoms. Two methods were used to detect SARS-CoV-2 in collected tear samples: viral culture, and a reverse transcription polymerase chain reaction (RT-PCR). The researchers also assessed any ocular symptoms present in the cohort, such as red eye and blurring of the vision.

Of the 17 COVID-19 patients, only one developed a red eye during this study. All patients tested negative for SARS-CoV-2 in tear samples, even though their nasopharyngeal swabs tested positive, suggesting that viral shedding via tears is unlikely.

The study authors said that “while from the study, the likelihood of viral transmission through tears is low, it should be noted that there are some caveats to the results. Most importantly, we only had one patient with ocular symptoms. Even though his tears tested negative, more studies involving patients with ocular symptoms should be conducted.” Other caveats include the lower diagnostic sensitivity associated with tests involving tear samples, and that the study only examined tear samples collected later in COVID-19 symptom development.

“Studies that are as small as this always have to be taken with a caveat,” said Stephen McLeod, a professor of Ophthalmology at the University of California, San Francisco (UCSF). McLeod is also a spokesperson for the American Academy of Ophthalmology, and the editor-in-chief for the Ophthalmology journal, in which this study was published. “Generally, Ophthalmology would typically think carefully about publishing a [study] with numbers as small as this, but we’re in a situation where we have to use the best available evidence that we have right now to help guide clinical decision-making.”

In particular, this presents a unique situation for ophthalmologists who may encounter asymptomatic COVID-19 patients.

“The specific challenge that ophthalmology faces is that we do a lot of our examinations necessarily in very close face-to-face proximity, and so there really has to be a great deal of attention paid to protecting the ophthalmologists,” said McLeod. “[…] The most challenging area has been the fact that guidelines for the use of elements of PPE, for example, masks, are based on the best available evidence in ambulatory practices in general.”

While the risk of SARS-CoV-2 transmission via tears is currently deemed low, the American Academy of Ophthalmology currently recommends that ophthalmologists should immediately cancel all non-emergent treatments, and that strict infection control measures should be applied, including the use of breath shields and slit-lamp barriers. Similarly, the World Health Organization recommends that healthcare workers should wear eye protection, such as goggles or a face shield, when collecting and handling laboratory specimens from patients with suspected COVID-19.

As for everyone else, it’s still important to wash your hands, disinfect surfaces, and avoid touching your face (especially your eyes, nose and mouth) to prevent accidental transmission. As you may know, this is easier said than done. I only touched my face about ten times while writing this.

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