A new Turkish study has raised concerns that Pfizer-BioNTech's COVID-19 vaccine may have subtle but serious side effects on the cornea. The research examined changes in the corneas of at least 64 patients before and after receiving both doses of the vaccine.
According to the scientists involved in the study published in the journal Ophthalmic Epidemiology, even though no immediate vision loss was reported, the vaccine led to thicker corneas, a reduced number of endothelial cells, and structural changes that could affect eye health over time.
The Daily Mail reported the changes in the eyes suggest the Pfizer vaccine may temporarily weaken the endothelium, even though patients did not suffer clear vision issues when the study was being conducted. Scientists said that for those with healthy eyes, these small changes likely may not affect vision right away. However, they may lead to corneal swelling or blurry vision, especially in those with pre-existing eye issues or those who have had a corneal transplant.
Researchers found that the average thickness of the cornea increased from 528 to 542 micrometres after two Pfizer doses, which is around a rise of 2 per cent. The endothelial cell count, which is responsible for keeping the cornea clear, dropped by about 8 per cent, from 2,597 to 2,378 cells per square millimetre.
Scientists urge caution
According to the study, which analysed the eye health with the help of Sirius corneal topography and Tomey EM-4000 specular microscopy, there is no need to halt the vaccination efforts. Scientists have rather called for ongoing monitoring of corneal health in those who already battle vulnerabilities in their eyes.
The researchers have also emphasised that the changes observed can be temporary responses to stress or inflammation that may resolve over time. Still, they warned that "the endothelium should be closely monitored in those with a low endothelial count or who have had a corneal graft", especially if future studies confirm long-term damage.
The Daily Mail said it also adds to existing concerns over rare side effects of mRNA vaccines, which include myocarditis and pericarditis, especially among younger men. The researchers plan to continue tracking participants to determine if these early corneal changes progress or stabilize over time.
Healthy endothelial cells are usually shaped like hexagons, which allows them to fit together tightly, like a honeycomb. Although the two per cent drop was not a direct sign of damage, it did suggest to the team that the cells may be reacting to some sort of stress over a significant period of time, like two months to three months.
Researchers also said their results showed evidence that the changes had a high likelihood of being directly linked to taking the vaccine, meaning it was not just a random anomaly in the testing. If the signs of stress and inflammation drop off shortly after receiving the Pfizer shot, the impact of these minor changes would not be overly harmful.
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