As much of the world enacts restrictions to stem the spread of COVID-19, we thought we’d share something a little different than our usual highlight of Phoenix MICRON® research. Ivan Seah and Rupesh Agrawal recently published a review on the ocular implications of coronaviruses. Not much is known about ocular infection or transmission of the coronavirus family; more research is needed to determine whether the eyes are an infection route or if tears could be used as a diagnostic.
Seah and Agrawal briefly but thoroughly explain the traits of coronavirus, the evidence for ocular infection in humans, and ocular infection research in animals. The coronavirus is a large RNA virus with a crown-like appearance. COVID-19 and the SARS virus of 2003-4 (both coronaviruses) mostly target the respiratory tract which is the focus of much of the research due to life-threatening implications.
There is some evidence in sparse research during the SARS epidemic in 2003-4 that SARS was present in tears which could then infect others, especially concerning for health-care workers. How the eyes become infected is not known; virus-laded droplets may have landed in the eye or the it may have systemically worked its way through the nasolacrimal gland. Some SARS cases presented with conjunctivitis; there has been at least one documented case of COVID-19 presenting with conjunctivitis as well. The ocular-coronavirus human research is very sparse and unfortunately mostly stopped after the SARS epidemic subsided.
The animal research is slightly more definitive. There is a cat coronavirus that commonly presents with conjunctivitis and a mouse coronavirus that so reliably causes retinopathy that it is a model of retinal degeneration (experimental coronavirus retinopathy or ECOR).
Taken together, the human and animal data suggests that coronaviruses can both infect and be transmitted from the eye. More research is needed to assess the risk of infection to and from the eyes, monitoring and treatment of the eyes during infection, and if tears could be used as a diagnostic route.
Citation: Ivan Seah & Rupesh Agrawal (2020): Can the Coronavirus Disease 2019 (COVID-19) Affect the Eyes? A Review of Coronaviruses and Ocular Implications in Humans and Animals, Ocular Immunology and Inflammation, DOI: 10.1080/09273948.2020.1738501