In December of 2019, as everyone is getting ready for the holidays, China was dealing with its first cases of a novel coronavirus. By March 2020, COVID-19 (caused by the virus named SARS-CoV-2) became a global pandemic with doctors and scientists scrambling to contain its rapid transmission. We currently know this strain of the novel coronavirus spreads through liquid droplets that come out when a person coughs or sneezes. But there are still many unknowns associated with COVID-19. Does it have other ways of spreading to people? One recent study published in Ophthalmology, the journal of the American Academy of Ophthalmology, hypothesized that COVID-19 could travel through the eyes and to our lungs.
The research authors recruited seventeen patients in a Singapore hospital who all tested positive for COVID-19. Patients were routinely swabbed behind the nose and above the throat to test for continued presence of the coronavirus. Patient information was obtained through their medical records including any known COVID-19 symptoms such as coughing, difficulty breathing, runny nose, and a sore throat.
To check their hypothesis, the research authors observed any eye problems the patients had during the study. They wanted to compare eye conditions previously reported with COVID-19 diagnoses such as red eyes, tearing, blurry eyes, eye mucus, and losing the ability to see vivid colors.
The research authors also wanted evidence of the novel coronavirus being present in the eye. Sixty-four tear samples were collected in tubes from when the patients first showed symptoms to their recovery twenty days later. They gathered twelve samples the first week, twenty-eight samples the second week, and twenty-four samples the third week. Researchers then performed a laboratory test where they took the tears apart microscopically to detect and isolate specific parts of the SARS-CoV-2 genome to identify it, like a fingerprint.
Laboratory tests of the tear samples showed no presence of COVID-19 in the eyes of all seventeen patients. One patient did show eye irritation and swelling, but this may have been a separate issue as the patient’s tear sample was negative for the novel coronavirus. Despite the negative COVID-19 results in the eyes, COVID-19 was present in all patients when swabbed above the throat and behind the nose. Fourteen out of the seventeen patients with COVID-19 showed symptoms of coughing, running, and a sore throat.
The research authors concluded that the possibility of COVID-19 spreading through our eyes and tears is very low—but not impossible. The study design had several limitations that make it difficult to absolutely say that COVID-19 cannot travel from the eyes and into the lungs. For example, there is evidence of pink eye showing up in 1%-3% of patients diagnosed with the novel coronavirus. Unfortunately, the study authors were unable to test for pink eye because they only collected tear samples. The research authors did write that future studies should focus on pink eye as a potential indicator of the novel coronavirus being inside the eye. This would involve collecting tissue samples from the inside surface of the eyelids in patients diagnosed with COVID-19. In addition, the number of patients in the study was very low. This raises concerns of results changing over time if more patients were to be recruited in the future.
We are learning more about COVID-19 everyday but stopping the virus continues to be an uphill battle. Scientists are months away from creating a vaccine. Remaining at home, washing our hands, and keeping our physical distance from others can help slow down the number of cases flooding our hospitals. If people need to go outside, we still need to be cautious of not touching our faces, including our eyes.