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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Schlick, Sarah, Lucio, Marianna, Wallukat, Gerd, Bartsch, Alexander, Skornia, Adam, Hoffmanns, Jakob, et al. (2022). Post-COVID-19 Syndrome: Retinal Microcirculation as a Potential Marker for Chronic Fatigue.. International journal of molecular sciences. https://doi.org/10.3390/ijms232213683
BibTeX
@article{mecfsatlas-schlick-2022-post-covid,
author = {Schlick, Sarah and Lucio, Marianna and Wallukat, Gerd and Bartsch, Alexander and Skornia, Adam and Hoffmanns, Jakob and Szewczykowski, Charlotte and Schröder, Thora and Raith, Franziska and Rogge, Lennart and Heltmann, Felix and Moritz, Michael and Beitlich, Lorenz and Schottenhamml, Julia and Herrmann, Martin and Harrer, Thomas and Ganslmayer, Marion and Kruse, Friedrich E and Lämmer, Robert and Mardin, Christian and Hohberger, Bettina},
title = {Post-COVID-19 Syndrome: Retinal Microcirculation as a Potential Marker for Chronic Fatigue.},
journal = {International journal of molecular sciences},
year = {2022},
doi = {10.3390/ijms232213683},
note = {PubMed: 36430175},
url = {https://www.mecfsatlas.com/evidence/schlick-2022-post-covid},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/schlick-2022-post-covid
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