The coronavirus appears unable to grow in certain eye tissues, according to new research from Washington University.
Other viruses, including herpes, can infect the clear protective layer of the eye known as the cornea, causing severe scarring and blindness.
Unexplained eye infections among COVID-19 patients, coupled with the fact that the coronavirus can easily invade other organs in the body, has led some doctors to wonder if the virus is multiplying within the eye itself. Based on lab tests using human corneas, however, a team of researchers at Washington University has found no evidence that the tissue serves as an entry point for the coronavirus.
Exposure to tiny mucus droplets from coronavirus-infected patients is thought to be the main way the virus spreads from person to person.
Several studies have detected coronavirus particles in human tears, while others have reported pink eye infections among COVID-19 patients. But so far, it’s been unclear whether the delicate tissues of the eyes might be susceptible to infection.
The Wash U team decided to take a direct approach to the question, slicing up corneas from human donors and exposing each fragment to a different virus, including the coronavirus and herpes and Zika viruses.
Both herpes and Zika were able to grow in the corneas, but the tissue was “completely resistant” to the coronavirus, said Dr. Jonathan Miner, a virologist at Washington University and study co-author.
“That doesn’t mean that it’s impossible, but it does demonstrate that the cornea doesn’t support growth of the coronavirus,” Miner said, which suggests the “cornea is less likely to be a route of entry for the virus.”
While it’s possible the coronavirus can infect other eye tissues, such as the tear ducts or lining of the eyelids, Washington University ophthalmologist and co-author Dr. Rajendra Apte said it’s encouraging that the cornea appears to be somewhat resistant to the virus.
“This just gives us some pause and some comfort that there are some resistance mechanisms,” Apte said. The cornea is most commonly transplanted tissue worldwide, he added, and these preliminary results suggest the coronavirus is probably not spreading via corneal transplants.
Still, the research team cautions that the study does not rule out the possibility of coronavirus transmission via other eye tissues.
“Until we have definitive evidence that it cannot be transmitted via droplet exposure to the eye, the safest thing is to presume that it might be possible,” Miner said.
The Centers for Disease Control and Prevention recommends health care workers wear protective eyewear, such as goggles or a face shield, when working with patients.
Although the agency has stopped short of issuing these recommendations for the general public, Dr. Anthony Fauci, the nation’s leading infectious disease expert, said in an interview in July that Americans should consider using eye protection when possible.
"You have mucosa in the nose, mucosa in the mouth, but you also have mucosa in the eye," Fauci said. "Theoretically, you should protect all the mucosal surfaces. So if you have goggles or an eye shield you should use it."
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