A new study has found traces of Covid-19 in conjunctival swabs and tears from coronavirus-positive patients.
The study, published in The Ocular Surface journal, aimed to analyze the prevalence of Covid-19 in post-mortem human eye tissues.
A research team led by Shahzad Mian, an ophthalmologist at the Kellogg Eye Center, found that the virus can infiltrate corneal tissue, the transparent outer layer of the eye, which could be used for transplants. This has raised concerns that the disease could be transmitted to a healthy recipient on the cornea.
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Study design
Of the 132 eye tissues from 33 donors destined for surgery in Michigan, Illinois, Ohio and New Jersey, 13 percent were positive for Covid-19.
The study donors were divided into three cohorts:
Group 1: This group was positive for Covid-19 after receiving a nasopharyngeal smear at the time of corneal recovery.
Group 2: This group was made up primarily of donors since the beginning of the pandemic when testing was not widely available. Most of these donors had a negative Covid-19 test.
Group 3: This group had no signs or symptoms of Covid-19 and tested negative, but also spent a lot of time with someone who tested positive.
This is significant because 15 percent of Group 2 cornea samples had traces of Covid-19 RNA, despite having a negative nasopharyngeal smear test. In particular, this was higher than the presence of Group 1 coronavirus-infected corneal tissue, which only had an 11 percent positivity rate despite donors having positive nasopharyngeal swab tests.
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Neither of the tissues from the two Group 3 donors had traces of Covid-19 RNA.
“An initial goal of the study was to test the efficacy of povidone-iodine, a disinfectant, in inactivating Covid-19,” Mian said.
“A larger study is needed to confirm our findings, but we are excited about the possible implications of this research. These questions are important to keep our patients healthy and safe, ”added Mian.
Researchers have not yet discovered whether the presence of Covid-19 RNA is due to an infection of the ocular surface or to the transport of the virus from the upper respiratory tract through the tear ducts.