Creator: DADO RUVIC | Credit: REUTERS

A recent study conducted in Turkey has brought attention to a potential association between the administration of the Pfizer COVID-19 vaccine and temporary alterations in corneal health, specifically noting changes such as transient corneal edema and fluctuations in corneal endothelial cell density. These findings raise important concerns, particularly for individuals who already suffer from pre-existing ocular conditions or who have undergone corneal transplants, as such patients may be more vulnerable to these post-vaccination ocular effects and should therefore be monitored with heightened care following immunization.

After several recent studies on the health dangers of COVID-19 vaccines, a new study from Turkey has added to the speculation of potential, albeit mild side-effects, regarding the Pfizer-BioNTech COVID-19 vaccine and its effect on eye health. The authors published their study in the journal, Ophthalmic Epidemiology, and were able to point toward subtle changes (however still concerning) in the cornea (the transparent front part of the eye). There were no immediate changes to quality of vision.

Changes in their corneal health

The researchers participated in a study that examined the eyes of 64 individuals at multiple points before and after receiving both doses of the Pfizer vaccine. The researchers referred to the changes in the participants’ corneal health as “not visually evident” but statistically measurable, including but not limited to: potential corneal thickening, reduced endothelial cell density (the cells that regulate corneal clarity), and changes to cell morphology.

The research indicated that there was a negligible 2 per cent increase in corneal thickness (from 528 to 542 micrometres); however, there was a larger than 8 per cent decrease in the overall endothelial cell count (from 2597 to 2378 cells/mm2), and it is significant because endothelial cells are responsible for regulating fluid and keep the cornea clear. In the long run, loss of endothelial cells may lead to swelling, blurry vision, or potential complications for patients with pre-existing eye disease. 

Side Effects of the Pfizer COVID-19 Vaccine 

While the study did not identify any patients who lost vision due to the study or vaccine effects, the investigators stated that, “the subtle changes could be indicators of stress/inflammation related to the vaccine,” and that those effects would likely be transient. They stated the need for regular monitoring, especially for patients with already low endothelial cell counts or people who have had corneal transplants. 

Ultimately, the data were obtained using ocular imaging technologies that examine the eye at a microscopic level, including Sirius corneal topography and Tomey EM-4000 specular microscopy. The researchers illustrate that the data are not grounds to cease vaccine use, particularly because the risk/benefit of the COVID-19 vaccine is worth the challenge; however, they noted they should be continuously monitored and researched.

The study also contributes to a wider conversation about infrequent side effects of mRNA vaccinations like the Pfizer and Moderna vaccines. Although these vaccines have been largely safe and efficacious, they have been associated with rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart), especially among younger males and post vaccine Post-vaccine-related myocarditis results show there is no considered or accepted effect of the vaccination to date.

In this case, researchers recognized that endothelial cells, once shaped as hexagons, can manifest subtle structural stress post vaccination. While two percent is not a dangerous reduction in cell number, it can be a signal of a systemic response to sustaining low-grade stress over weeks or months.

The scientists also indicated their findings were not likely coincidental, and presented a propensity to indicate the vaccine was the source of the changes. Emphatically, the study intends to follow up with the subjects from the study to see if these initial changes are habitual or return to their baseline kinetic position.

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