Turkish researchers have discovered that Pfizer’s covid-19 vaccine can cause changes in the eye’s cornea that could potentially lead to vision problems. The study, which followed 64 people over three months, shows that the vaccine can make the cornea thicker and reduce the number of important cells that keep vision clear.
The researchers measured changes in the cornea’s inner layer, the endothelium, before the first vaccine dose and two months after the second dose. The results showed that both doses led to thicker corneas, fewer endothelial cells, and greater variation in cell size.
Specifically, corneal thickness increased from 528 to 542 micrometers – an increase of approximately two percent. At the same time, the number of endothelial cells decreased from 2,597 to 2,378 cells per square millimeter, a loss of about eight percent.
“The endothelium should be closely monitored in those with low endothelial cell counts or who have undergone corneal transplantation,” the researchers warn in the study published in the journal Ophthalmic Epidemiology.
Short-term impact without symptoms
In the short term, the changes suggest that Pfizer’s vaccine may temporarily weaken the endothelium, even though patients did not experience any clear vision problems during the study period. For people with healthy eyes, these small changes are unlikely to affect vision immediately.
However, if the changes persist for several years, they could lead to corneal swelling or blurred vision, particularly in people with existing eye problems or those who have undergone corneal transplantation. A thicker cornea and reduced cell density can contribute to conditions such as corneal edema or corneal decompensation, which in severe cases can cause permanent vision loss.
Need for long-term studies
The research team emphasizes the importance of long-term studies to see if the changes persist months and years after vaccination. An ophthalmologist can use special microscopy to check if someone has a low endothelial cell count.
The study adds to a growing list of concerns regarding Pfizer’s covid vaccine. In May, the US Food and Drug Administration (FDA) forced Pfizer and Moderna to expand warning labels about risks of heart damage, particularly for men between 16 and 25 years old.
