The virus that causes COVID-19 can breach the protective blood-retinal barrier, leading to potential long-term consequences in the eye, new research shows.
The blood-retinal barrier is designed to protect our vision from infections by preventing microbial pathogens from reaching the retina where they could trigger an inflammatory response with potential vision loss.
Pawan Kumar Singh, an assistant professor of ophthalmology at the University of Missouri, leads a team researching new ways to prevent and treat ocular infectious diseases.
Using a humanized ACE2 mice model, the team found that SARS-CoV-2, the virus that causes COVID-19, can infect the inside of the eyes even when the virus doesn’t enter the body through the surface of the eyes.
Instead, they found that when viruses enter the body through inhalation, it not only infects organs like lungs, but also reaches highly protected organs like eyes through the blood-retinal barrier by infecting the cells lining this barrier.
“This finding is important as we increase our understanding of the long-term effects of SARS-CoV-2 infection,” says Singh. “Earlier, researchers were primarily focused on the ocular surface exposure of the virus.
“However, our findings reveal that SARS-CoV-2 not only reaches the eye during systemic infection but induces a hyperinflammatory response in the retina and causes cell death in the blood-retinal barrier. The longer viral remnants remain in the eye, the risk of damage to the retina and visual function increases.”
Singh also discovered that extended presence of SARS-CoV-2 spike antigen can cause retinal microaneurysm, retinal artery and vein occlusion, and vascular leakage.
“For those who have been diagnosed with COVID-19, we recommend you ask your ophthalmologist to check for signs of pathological changes to the retina,” Singh says. “Even those who were asymptomatic could suffer from damage in the eyes over time because of COVID-19 associated complications.”
While viruses and bacteria have been found to breach the blood-retinal-barrier in immunocompromised people, this research is the first to suggest that the virus that causes COVID-19 could breach the barrier even in otherwise healthy individuals, leading to an infection that manifests inside the eye itself.
Immunocompromised patients or those with hypertension or diabetes may experience worse outcomes if they remain undiagnosed for COVID-19 associated ocular symptoms.
“Now that we know the risk of COVID-19 to the retina, our goal is to better understand the cellular and molecular mechanisms of how this virus breaches the blood-retinal barrier and associated pathological consequences in hopes of informing development of therapies to prevent and treat COVID-19 induced eye complications before a patient’s vision is compromised,” Singh says.
The study appears in the journal PLOS Pathogens.
The National Institutes of Health/National Eye Institute and the University of Missouri funded the work.
Source: University of Missouri
