A new study shows that SARS-CoV-2 can be detected on the ocular surface in patients with COVID-19, even when the nasopharyngeal swab is negative.
The authors of the study, led by Claudio Azzolini of the Unit of Ophthalmology, Department of Medicine and Surgery, University of Insubria, Italy, collected the tears of 91 people admitted to hospital with the coronavirus via a “conjunctival swab.”
The study, published in the journal JAMA Ophthalmology found that SARS-CoV-2 was present on the ocular surface in 52 of 91 patients with COVID-19 (57.1 percent).
According to the researchers, SARS-CoV-2 RNA was found on the ocular surface in a large part of the cohort of patients with COVID-19, although the infectivity of this material could not be determined.
“Because patients may have positive test results with a conjunctival swab and negative results with a nasopharyngeal swab, use of the slightly invasive conjunctival swab may be considered as a supplementary diagnostic test,” they said.
They added that there was a wide variability in the average viral load from both eyes.
“The virus was present in both eyes in 31 of 52 patients. Several patients (22 of 31 or 71 percent) had a slight difference in viral load values between the two eyes.
“A discrepancy in conjunctival swab results within the same patient (i.e., one eye positive and one eye negative) was observed in 21 of 91 patients (23.1 percent); a viral load greater than 50 copies/μL was detected in one eye.
“The highest viral load of a single eye (up to 90,000 copies/μL) was found in patients with the virus detected in both eyes.
“The lowest value of viral load found in patients considered positive for the conjunctival swab (58 copies/μL) was found in patients in whom the virus was detected in one eye only,” they said.
However, they found no association between virus detection and comorbidities at COVID-19 diagnosis.
“A slightly higher prevalence of ocular signs or symptoms of surface inflammation in at least one eye was present among patients with positive conjunctival swab results than among those with negative conjunctival swab results.
“Neither the hospital department type nor the respiratory device at the time of conjunctival swab was associated with the presence of the virus on the ocular surface,” they said.
Commenting on the study, a Senior Registrar at the Department of Ophthalmology, University of Ilorin Teaching Hospital, Dr. Lawal Ismail, said though the study showed that the virus could be detected on the ocular surface, the diagnosis is still not widely accepted.
“COVID-19 is a new virus and new studies are coming up. I also learnt recently that China is trying to study if the virus can be detected from stool.
“So many people are carrying out studies. Yes, some studies have shown that the virus can be detected on the ocular surface of patients but they are not widely accepted.
“There is no strong scientific evidence to that effect yet. So, we will need additional studies for a strong evidence,” Ismail said.
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