The COVID-19 virus penetrates the blood-retinal barrier and can damage vision

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The blood-retinal barrier is designed to protect our vision from infections by preventing microbial pathogens from reaching the retina where they can cause an inflammatory response with possible vision loss. But researchers at the University of Missouri School of Medicine have found that the virus that causes COVID-19 can breach this protective retinal barrier with possible long-term consequences for the eye.

Pawan Kumar Singh, PhD, assistant professor of ophthalmology, leads a team researching new ways to prevent and treat eye infectious diseases. Using a humanized ACE2 mouse model, the team found that SARS-CoV-2, the virus that causes COVID-19, can infect the lining of the eyes even if the virus does not enter the body through the ocular surface. Instead, they discovered that when viruses enter the body through inhalation, it not only infects organs such as the lungs, but also reaches highly protected organs such as the eyes through the blood-retinal barrier by infecting the cells along this barrier.

“This finding is important as we advance our understanding of the long-term effects of SARS-CoV-2 infection,” Singh said. “Previously, researchers focused mainly on the exposure of the ocular surface to the virus. However, our findings show that SARS-CoV-2 not only reaches the eye during systemic infection, but also induces a hyperinflammatory response in the retina and causes cell death in the blood-retinal barrier. The longer virus residues remain in the eye, the risk of damage to the retina and visual function increases.”

Singh also found that prolonged presence of SARS-CoV-2 spike antigen can cause retinal microaneurysm, retinal artery and vein occlusion, and vascular leakage.

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“For those who have been diagnosed with COVID-19, we recommend that you ask your ophthalmologist to check for signs of pathological changes in the retina,” Singh said. “Even those who were asymptomatic could develop eye damage over time due to COVID-19-related complications.”

Although viruses and bacteria have been shown to breach the blood-retinal barrier in immunocompromised people, this study is the first to suggest that the virus that causes COVID-19 could breach the barrier even in otherwise healthy individuals, leading to infection which manifests itself in the eye itself. Immunocompromised patients or those with hypertension or diabetes may experience worse outcomes if they are not diagnosed for COVID-19-associated eye 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 the hope of ameliorating the development of inform therapies to prevent and treat eye complications caused by COVID-19 before a patient’s vision is affected,” Singh said.

Reference: Monu M, Ahmad F, Olson RM, Balendiran V, Singh PK. SARS-CoV-2 infects cells lining the blood-retinal barrier and induces a hyperinflammatory immune response in the retina via systemic exposure. PLOS pathogens. 2024;20(4):e1012156. doi: 10.1371/journal.ppat.1012156

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