Non-Hospitalized Long COVID Patients Exhibit Reduced Retinal Capillary Perfusion: A Prospective Cohort Study, 2025, Lyons et al.

SNT Gatchaman

SNT Gatchaman

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Non-Hospitalized Long COVID Patients Exhibit Reduced Retinal Capillary Perfusion: A Prospective Cohort Study
Lyons, Clayton E.; Alhalel, Jonathan; Busza, Anna; Suen, Emily; Gill, Nathan; Decker, Nicole; Suchy, Stephen; Orban, Zachary; Jimenez, Millenia; Perez Giraldo, Gina; Koralnik, Igor J.; Gill, Manjot K.

The mechanism of post-acute sequelae of SARS-CoV-2 (PASC) is unknown. Using optical coherence tomography angiography (OCT-A), we compared retinal foveal avascular zone (FAZ), vessel density (VD), and vessel length density (VLD) in non-hospitalized Neuro-PASC patients with those in healthy controls in an effort to elucidate the mechanism underlying this debilitating condition.

Neuro-PASC patients with a positive SARS-CoV-2 test and neurological symptoms lasting ≥6 weeks were included. Those with prior COVID-19 hospitalization were excluded. Subjects underwent OCT-A with segmentation of the full retinal slab into the superficial (SCP) and deep (DCP) capillary plexus. The FAZ was manually delineated on the full slab in ImageJ. An ImageJ macro was used to measure VD and VLD. OCT-A variables were analyzed using linear mixed-effects models with fixed effects for Neuro-PASC, age, and sex, and a random effect for patient to account for measurements from both eyes. The coefficient of Neuro-PASC status was used to determine statistical significance; p-values were adjusted using the Benjamani–Hochberg procedure.

Neuro-PASC patients (N = 30; 60 eyes) exhibited a statistically significant (p = 0.005) reduction in DCP VLD compared to healthy controls (N = 44; 80 eyes). The sole reduction in DCP VLD in Neuro-PASC may suggest preferential involvement of the smallest blood vessels.

Link | PDF (Journal of Imaging) [Open Access]
 
Lower retinal VLD has been reported to exhibit a significant relationship with worse cerebrovascular reactivity, reduced perfusion of the middle cerebral artery on brain MRI, and reduced cognitive function. These findings suggest Neuro-PASC patients may have an underlying reduction in small vessel perfusion in the brain contributing to their observed neurologic symptoms. It is important to note that studies investigating brain MRI findings in PASC patients have largely been negative or inconclusive. Vasilev et al. identified several studies that found white matter lesions—a marker of small vessel disease in the brain—in PASC patients but failed to show a correlation between these lesions and neurologic symptoms. The lack of findings on brain MRI does not invalidate our findings of reduced DCP VLD in Neuro-PASC patients, as OCT-A evaluates the exquisitely small retinal microvasculature in a quantitative way that cannot be achieved by conventional brain MRI. It is possible that the reduced capillary perfusion in NeuroPASC is too mild to be captured by MRI and can only be identified on OCT-A within the CNS, particularly in those individuals who did not require hospitalization for their initial COVID-19 infection.
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Not the first study looking at this (Hohberger, Scheibenbogen, Schmaderer and others have also explored OCT-A). It seems this study lacks a couple of details. In similar studies it had been discussed that things like obesity could influence the results and with the lack of detail on the cohort here it's hard to understand whether that might have played a role here as well.
 
Moved post

Northwestern Medicine: ''New research from Northwestern Medicine reveals link between long COVID and eye health'

'..found that patients with long COVID experienced a significant reduction in the density of blood vessels in the back of the eye, compared to healthy individuals'

“The change in blood vessels in the deep part of the retina supports the hypothesis that long COVID affects similar blood vessels in other parts of the body, like the brain, which can potentially contribute to the symptoms of long COVID such as memory loss, brain fog and fatigue.”

'In patients with long COVID, researchers found that the most significant change was a decrease in blood flow in the smallest blood vessels in the deeper layers of the retina. Researchers believe this decrease in circulation may be reflective of decreased blood circulation in the brain, which may lead to neurologic symptoms.'

'Building on these findings, researchers are launching a longitudinal study that will examine how the changes in the deep retinal blood vessels relate to patient symptoms and other established markers of long COVID.'

'This issue affects an estimated 17 million adults in the U.S. and comes with significant healthcare and economic burdens, costing about $600 million in lost wages,” said Igor Koralnik, MD
 
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