A new study has raised concerns about potential eye-related side effects following the Pfizer-BioNTech COVID-19 vaccine, suggesting it may cause subtle, short-term changes in the cornea—the clear, outermost layer of the eye responsible for focusing light.
What Did the Study Find?
Researchers in Turkey conducted a small observational study involving 64 individuals, examining their corneal endothelium (the innermost layer of the cornea) before their first vaccine dose and again two months after the second. The corneal endothelium plays a key role in keeping the cornea clear by pumping out excess fluid.
Key findings included:
- Corneal thickness increased from 528 to 542 micrometers (about 2%).
- Endothelial cell count decreased by about 8%, from 2,597 to 2,378 cells/mm².
- Cell shape uniformity declined, with fewer cells maintaining a healthy six-sided (hexagonal) shape—dropping from 50% to 48%.
- The coefficient of variation (a measure of how evenly sized the cells are) rose from 39 to 42, suggesting increased stress or irregularity in the layer.
Are These Changes Dangerous?
Currently, no participants reported vision problems during the short-term study period. The corneal cell counts remained within the normal range (2,000–3,000 cells/mm²), which is generally considered safe for most people.
However, researchers emphasized caution:
- In individuals with pre-existing eye conditions, prior corneal transplants, or naturally low endothelial cell counts, these changes could pose a higher risk.
- Long-term consequences remain unknown, as the study only tracked changes up to two months after full vaccination.
Persistent changes in corneal thickness or endothelial cell loss could increase the risk of corneal edema, bullous keratopathy, or corneal decompensation, all of which may cause vision loss if untreated.
What Should People Do?
Researchers do not advise against vaccination but recommend that:
- Individuals with eye surgeries, Fuchs’ dystrophy, or corneal grafts monitor their corneal health.
- Specular microscopy, a non-invasive imaging test used by eye doctors, can help detect low cell counts or unhealthy endothelial layers.
If you experience blurry vision, eye discomfort, or have had previous corneal issues, consulting an ophthalmologist may be wise, especially after receiving a vaccine.
Conclusion
While the Pfizer vaccine remains safe and effective, this study highlights a need for continued research into its long-term effects on the eyes, particularly in vulnerable individuals. For the general population with healthy eyes, these minor changes are unlikely to impact vision—but should be watched carefully in future studies.
