International, News, Ophthalmology, Optometry, Research

Cornea resistant to the novel coronavirus – study

A new study has suggested the cornea can resist infection from the novel coronavirus, in findings that bode well for corneal transplants and similar procedures.

Researchers from the Washington University School of Medicine in St Louis wanted to see how SARS-CoV-2 interacted with the cornea after previous studies established that herpes simplex virus can infect the cornea and spread to other parts of the body in immunocompromised patients, and Zika virus was found in tears and corneal tissue.

Although SARS-CoV-2 – the virus that causes COVID-19 – does not appear to replicate in the human cornea, they have yet to determine whether other ocular tissue, such as the tear ducts and the conjunctiva, are vulnerable to the virus.

“Our findings do not prove that all corneas are resistant,” first author Dr Jonathan Miner said. “But every donor cornea we tested was resistant to the novel coronavirus. It’s still possible a subset of people may have corneas that support growth of the virus, but none of the corneas we studied supported growth of SARS-CoV-2.”

Miner, an assistant professor of medicine, of molecular microbiology and of pathology and immunology, teamed up with ophthalmologist Dr Rajendra Apte to study mouse and human corneas exposed to the herpes simplex, Zika and SARS-CoV-2 viruses.

Dr Rajendra Apte says it’s not clear weather SARS-CoV-2 causes conjunctivitis or if it’s associated with secondary inflammation. Image: Washington University School of Medicine

“Some COVID-19 patients get eye symptoms, such as conjunctivitis (pinkeye), but it’s not clear that the viral infection itself causes that; it could be related to secondary inflammation,” Apte said.

“The cornea and conjunctiva are known to have receptors for the novel coronavirus, but in our studies, we found that the virus did not replicate in the cornea.”

Apte and Miner also identified key substances in corneal tissue that can promote or inhibit viral growth.

One inhibitor they identified is called interferon lambda. They found that it prevented efficient growth of Zika virus and herpes simplex virus in the cornea. But with SARS-CoV-2, levels of the substance had no effect on whether the virus could replicate. It could not gain a foothold whether interferon lambda was present or not.

Apte said it suggested COVID-19 probably cannot be transmitted through a cornea transplant or similar procedures in the eye.

“Our data suggest that the novel coronavirus does not seem to be able to penetrate the cornea,” Apte said.

Miner added, however, that because of unknowns involving the tear ducts and the conjunctiva, it’s too soon to dismiss the importance of eye protection.

“It’s important to respect what this virus is capable of and take appropriate precautions,” he said. “We may learn that eye coverings are not necessary to protect against infection in the general community, but our studies really are just the beginning. We need larger clinical studies to help us better understand all the potential routes of SARS-CoV-2 transmission, including the eye.”

The findings were published November 3 issue of the journal Cell Reports.

More reading

COVID-19 detected after eye exams of asymptomatic patients

COVID-19 study examines true eye protection benefit

Phaco and surgeon contamination risks amid COVID-19

AMD patients at higher risk of COVID-19 death