It’s not a new question, but it is one that is gaining increased traction: Is there a link between Novo Nordisk’s diabetes superstar Ozempic and blindness?

After the recent release of two independent studies from the University of Southern Denmark (SDU) suggested the use of Ozempic increases patients' chances of developing a rare eye disorder, the European Union has decided to investigate, according to a report from Reuters.

The decision came after the Danish Medicines Agency (DMA) asked the European Medicines Agency's Pharmacovigilance Risk Assessment Committee to review the information.

As of Dec. 10, the DMA had received a total of 19 reports in the country of nonarteritic anterior ischemic optic neuropathy (NAION), according to a Monday press release. The first report to describe NAION as a suspected adverse reaction to semaglutide—the active ingredient in both Ozempic and Novo’s Wegovy—was received in July.

NAION happens when blood flow is impaired, causing damage to the optic nerve and the sudden loss of vision in one eye. NAION most often occurs in people age 50 and older.

“After a thorough evaluation of the studies from the University of Southern Denmark and Novo Nordisk’s internal safety assessment, Novo Nordisk is of the opinion that the benefit-risk profile of semaglutide remains unchanged,” a company spokesperson said in an email.

The new reports come on top of a study published in July in JAMA Ophthalmology, which showed that among a group of 16,827 patients, those who took Ozempic were more likely to develop NAION than those receiving a non-GLP-1 drug for diabetes or obesity.

That observational study, which was conducted by researchers at Harvard, concluded that there was an “association” between semaglutide and NAION. The researchers added that “future study is required to assess causality.”

In one of the recent studies, which was conducted in Denmark and Norway, researchers concluded (PDF) that the use of “semaglutide is associated to an increased risk of NAION, but also that the excess absolute risk is low.”

In the other new study, the researchers investigated data from 424,152 diabetic patients, of which one-fourth (106,454) received Ozempic and the rest received other types of diabetes medicines. It found that two people per 10,000 patients treated with semaglutide developed NAION versus one out of every 10,000 in the comparator group.

While the DMA explained that adverse reaction reports and earlier studies on NAION were not strong enough to indicate a possible link between the medicine and the symptoms, the results of the new SDU studies "reinforce this suspicion and may hold new important information that should be assessed," the agency said.

Novo's spokesperson added that the company “has conducted its own analysis across randomized controlled clinical trials with GLP-1 receptor agonists, including a blinded ophthalmologist evaluation to confirm NAION diagnoses. Through this analysis, very few cases of ophthalmologist-confirmed NAION cases were identified, with no imbalance disfavoring Novo Nordisk GLP-1 receptor agonists.”

Editor's note: This story was updated on Dec. 18 with information about the European Medicines Agency's decision to investigate.