Scientists have discovered that Pfizer’s COVID-19 jab may heighten the risk of severe eye damage, potentially leading to vision loss, according to a new study.

The new study from Turkish researchers specifically looked at how the vaccine affected patients’ corneas – the clear front part of the eye that allows light to come in. In 64 subjects, scientists measured changes in the cornea’s inner layer, called the endothelium, before taking the first Pfizer dose and two months after receiving the second. Results showed that taking two doses of the vaccine led to thicker corneas, fewer endothelial cells in the eye and more variation in the size of these specialised cells that form the endothelium.

In the short term, these changes indicate the Pfizer vaccine might temporarily weaken the endothelium, even though patients didn’t suffer obvious vision problems during the study. For people with healthy eyes, these small changes likely won’t affect vision immediately.

But, scientists said that if these changes last for years, they could lead to corneal swelling or blurry vision, especially in those with pre-existing eye conditions or people who have had a corneal transplant. A thicker cornea and reduced cell density may help cause eye conditions like corneal oedema, bullous keratopathy, or corneal decompensation, which can all cause permanent vision loss in severe cases, especially if left untreated.

The researchers warned in the study, published Wednesday in the journal Ophthalmic Epidemiology: “The endothelium should be closely monitored in those with a low endothelial count or who have had a corneal graft.”

However, the team did not recommend against the Pfizer vaccination and will still need to conduct long-term testing on more patients’ eye health to see if these changes continue to appear months and years after the jabs.

A spokesperson from Pfizer UK said they took the reports “very seriously”.

In a statement to the Express, they said: “Patient safety is paramount and we take any reports of adverse events very seriously. Adverse event reports do not imply causality, and in the context of vaccination such events may be unrelated to administration of the vaccine. Hundreds of millions of doses of the Pfizer-BioNTech COVID-19 vaccine have been administered globally and the benefit-risk profile of the vaccine remains positive for all authorised indications and age groups.

As with every medicine and vaccine, including the Pfizer-BioNTech COVID-19 vaccine, Pfizer has robust processes to meet its regulatory responsibilities to closely monitor, report and analyse all adverse events, and collect relevant information to assess any new potential safety risks that may be associated with the COVID-19 vaccine. In addition to our pharmacovigilance efforts and compliance with regulatory requirements related to quality and safety, we also work with regulatory authorities around the world as they independently monitor the safety profile of our vaccine.

Patients who receive the COVID-19 vaccine should talk to their doctor, pharmacist or nurse if they have any concerns or experience any side effects. This includes any possible side effects not listed in the package leaflet.”

Side effects can also be reported directly via the Yellow Card Scheme here.