A new study has found traces of Covid-19 in conjunctival swabs and tears of coronavirus positive patients.

The study, published in the journal The Ocular Surface, intended to analyse the prevalence of Covid-19 in human post-mortem ocular tissues.

A research team led by Shahzad Mian, an ophthalmologist at Kellogg Eye Centre, found that the virus can infiltrate corneal tissue, the clear, outer layer of the eye, that could be used for transplantation. This has raised concerns that the disease could be transmitted to a healthy recipient of the cornea.

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Study design

Of the 132 ocular tissues from 33 donors intended for surgery in Michigan, Illinois, Ohio, and New Jersey, 13 per cent were positive for Covid-19.

The study’s donors were divided into three cohorts:

Group 1: This group was positive for Covid-19 after receiving a nasopharyngeal swab at the time of corneal recovery.

Group 2: This group was primarily made up of donors from early in the pandemic when testing wasn’t widely available. The majority of these donors had a negative Covid-19 test.

Group 3: This group didn’t have signs or symptoms of Covid-19 and tested negative, but they also spent extended amounts of time with someone who tested positive.

This is significant because 15 per cent of the corneal samples from Group 2 had traces of Covid-19 RNA, despite having a negative nasopharyngeal swab test. Notably, this was higher than the presence of coronavirus-infected corneal tissue from Group 1, which only had a positivity rate of 11 per cent despite the donors having positive nasopharyngeal swab tests.

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None of the tissues from Group 3’s two donors had traces of Covid-19 RNA.

“An initial study goal was to test the effectiveness of povidone-iodine, a disinfectant, in inactivating Covid-19,” Mian said.

“A larger study is needed to confirm our findings, but we’re excited about this research’s potential implications. These questions are important in keeping our patients healthy and safe,” Mian added.

The researchers are yet to figure out whether the presence of Covid-19 RNA is due to ocular surface infection or due to transport of the virus from the upper respiratory tract via the tear ducts.

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