Reverse transcriptase-PCR tests rarely find conjunctival SARS-CoV-2
The virus that causes COVID-19, SARS-CoV-2, rarely appeared in the conjunctiva when tested by reverse transcriptase-polymerase chain reaction, according to a meta-analysis published in Optometry and Vision Science.
“The role of the eye and ocular system in COVID-19 is currently under intensive study as a potential transmission site on account of the natural exposure to potential airborne droplets and aerosols, as well as the anatomical relationship to the respiratory tract,” Nicole M. Sopp, OD, FAAO, and Vandhana Sharda, OD, MS, FAAO, of Atrius Health in Newton, Mass., wrote. “The ocular surface may act as a direct inoculation site, a conduit for the virus into the respiratory system or as a method of transmission from potentially infected conjunctiva or tears.”
Because concurrent cases of conjunctivitis and COVID-19 have been reported, Sopp and Sharda reviewed seven clinical studies where reverse transcriptase-polymerase chain reaction (RT-PCR) tests were performed on participants’ conjunctivas. Among these, positive RT-PCRs on the conjunctiva appeared in 1.6% to 7.1% of lab-confirmed COVID-19 cases. Conjunctivitis appeared in only 25 COVID-19 cases among 403 participants (estimated prevalence, 0.062; 95% CI, 0.041-0.09).
SARS-CoV-2 in the tears and conjunctiva was even less common, with a prevalence of 2.7% (95% CI, 1.4 to 4.8), which the researchers noted may indicate transmission through the eyes.
Sopp and Sharda also examined eight anecdotal case reports on the ocular impact of SARS-CoV-2, wherein some patients had conjunctivitis and positive conjunctival RT-PCR. However, two reports did not perform conjunctival swabs, and one report was unclear on whether COVID-19 was lab-confirmed.
One of the studies reported five cases of conjunctivitis with laboratory-confirmed COVID-19 and no other symptoms, which Sopp and Sharda wrote “is concerning but anecdotal at this time. No conjunctival cell analysis was performed, and it is possible that conjunctivitis was secondary to opportunistic infection or general immune response from the respiratory infection.”
Limitations included homogenous testing techniques across studies, publication bias, possible misdiagnosis of opportunistic conjunctival infection and small sample size.
Moving forward, Sopp and Sharda suggested investigating how the use of eyedrops, contact lenses and punctal plugs affect RT-PCR outcomes and prevalence. Clinically, they advised doctors to stay vigilant for concurrent conjunctivitis and COVID-19.
“Albeit conjunctivitis is not a common manifestation, clinicians should continue to obtain thorough review of systems and consider noncontact screening for fever,” they wrote. “Proper education on frequent handwashing to prevent transmission should still be provided following the pattern of any viral conjunctivitis. Clinicians should be aware of the uncommon but benign conjunctivitis that has been associated with COVID-19 to provide concerned patients palliative recommendations including cool compresses and artificial tears using telemedical strategies.”
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