Schlick, Sarah, Lucio, Marianna, Wallukat, Gerd et al. · International journal of molecular sciences · 2022 · DOI
Researchers studied whether tiny blood vessels in the eye could be a measurable sign of fatigue in people with long COVID. Using a special imaging technique to look at blood vessels in the retina (back of the eye), they found that people with long COVID—especially women—had reduced blood flow in these tiny vessels compared to healthy people. Those with long COVID who reported severe fatigue had even lower blood vessel density than those with milder fatigue, suggesting the eye scan might objectively confirm what patients report feeling.
ME/CFS and post-COVID syndrome lack objective biomarkers for fatigue severity, forcing clinicians to rely entirely on patient self-report. This study provides preliminary evidence that an objective, non-invasive eye imaging test could quantify a physiological correlate of fatigue, potentially improving diagnosis, stratification, and monitoring of treatment response in these patients.
This cross-sectional study cannot establish causation—it only documents association between reduced retinal blood flow and reported fatigue at a single timepoint. The study was conducted in post-COVID patients and does not prove the mechanism applies identically to ME/CFS or explain whether microcirculation changes cause fatigue or result from it. Validation in independent cohorts and longitudinal follow-up would be required before clinical adoption.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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