Small study suggests a low risk of COVID-19 transmission from tears

The authors conducted a small prospective study to observe whether or not COVID-19 patients treated at a Singaporean hospital had detectable virus in their tears. 

Study design

Investigators enrolled 17 patients infected with COVID-19 at various time points in the disease’s natural history. Sixty-four tear samples were collected with Schirmer’s strips between 3 to 20 days after the onset of COVID-19 symptoms, with the majority (52) of the samples collected between the first and third week.

Outcomes

Viral culture and real-time PCR assays did not detect SARS-CoV-2—the causative virus for COVD-19—in any of the tear samples, regardless of a patient’s positive nasopharyngeal PCR. Of particular interest was the negative result from a tear sample collected on day 17 from the only patient in the series with conjunctivitis, which developed after admission.

Limitations

Albeit timely amidst the growing pandemic, these highly preliminary results require validation by forthcoming studies with a much larger number of replicates at each time point in the natural history of COVID-19. The study’s viral detection methods may have also affected its accuracy in light of a different PCR assay and laboratory being used to test the tear samples and nasopharyngeal swabs; omission of conjunctival scrapings from the screening protocol may have also affected accuracy. Finally, the study’s convenience sampling, although employed out of necessity, resulted in the collection of relatively few data from COVID-19 patients during their first week of symptoms and no data from asymptomatic outpatients despite the potential importance of these subpopulations to emerging public health mitigation strategies.

Clinical significance

The negative results from both viral culture and PCR testing of tears collected from this small Singaporean cohort of 17 COVID-19 inpatients suggest that the virus may not be readily transmissible from ocular discharge. This is consistent with the current position held by both the World Health Organization and Centers for Disease Control, which describe respiratory droplets and their contact with oral, nasal or ocular mucosa as the primary mode of transmission.

Read an editorial on this paper, No Time for Tears, by Gerami Seitzman, MD, and Thuy Doan, MD, PhD.