Researchers in Singapore have found that the possibility of COVID-19 transmission through tears, regardless of the phase of infection, is low. All tear samples showed negative results, even when nasopharyngeal swab samples continued to show positive results. The tear sampling time points covered two weeks of active infection, which the researchers believe was a good representation of the full disease course. Patients with symptoms of upper respiratory tract infections did not demonstrate any viral shedding in tears, suggesting that the hypothesis of the lacrimal duct as a viral conduit may not be true.

Of the 17 patients examined in the study, none demonstrated ocular symptoms. Only one patient developed conjunctival injection and chemosis during their stay in the hospital. The upper respiratory tract symptoms 14 patients showed at presentation included cough, runny nose and sore throat.

The researchers believe future studies should involve more patients with ocular symptoms and also consider the association between serum viral load and viral shedding in tears. Their study did not analyze any blood samples because they were not part of the routine clinical investigation in patient management.