GLP-1 Drugs Face Scrutiny Over Rare Eye Condition Linked to Vision Loss

Global health regulators, researchers, and the US legal system are intensifying their examination of a potential link between GLP-1 receptor agonists and non-arteritic anterior ischaemic optic neuropathy (NAION), a rare condition characterized by sudden, painless vision loss. The condition occurs when blood flow to the optic nerve is disrupted. While the European Medicines Agency (EMA) formally classified NAION as a very rare side effect of semaglutide in June 2025, the scientific community remains divided over whether the drugs are the direct cause.

The EMA's safety committee concluded that NAION may affect up to one in 10,000 people taking semaglutide. This regulatory stance was informed by large epidemiological studies suggesting that adults with type 2 diabetes using the drug faced roughly double the risk of developing the condition compared to non-users. Following this, the UK medicines regulator updated product information to include the warning, advising patients to seek urgent medical attention if they experience sudden or rapidly worsening vision.

The EMA recommended that semaglutide product labeling list the condition as a very rare adverse effect and advised cessation upon confirmed diagnosis, though organizations like NANOS and the Academy noted potential health risks from stopping GLP-1 RA therapy for certain groups. Established systemic and vasculopathic risk factors for the condition include hypertension, diabetes mellitus, cardiovascular disease, hypercholesterolemia, smoking, metabolic syndrome, and obstructive sleep apnea.

Observational research has further fueled the debate. A 2026 systematic review and meta-analysis of over 14 million people with type 2 diabetes identified an increased risk of NAION among semaglutide users. A separate 2026 meta-analysis of eight observational cohorts involving nearly 5.9 million people reached similar conclusions. However, other reviews have reported lower or statistically insignificant increases in risk, highlighting the limitations of observational data in establishing direct causality.

Novo Nordisk has presented pooled analysis from its own randomized clinical trials to counter the observational findings. The company's analysis, covering 96,829 participants and over 205,000 participant-years, identified three confirmed NAION cases in the GLP-1 group and five in the placebo group. Novo Nordisk stated that this data did not show an increased incidence of the condition among those receiving treatment. In a statement to Business Today, the company noted, "Considering the totality of evidence from clinical trials, post-marketing reports and observational studies, alongside the generally low incidence rate of NAION, Novo Nordisk believes that the benefit-risk profile of semaglutide remains favourable."

Patients often present with a crowded or small optic disc characterized by a tiny or absent cup, which can predispose the optic nerve to ischemia. In the United States, estimated annual incidence figures range from 2.3 to 10.2 per 100,000 individuals over 50 years old, and it represents the most frequent cause of acute optic nerve injury in people above 50.

the issue has entered the US court system. As of September 1, 2026, 216 federal lawsuits alleging that GLP-1 medicines caused NAION have been consolidated into multidistrict litigation in the Eastern District of Pennsylvania. The litigation targets products from both Novo Nordisk and Eli Lilly, including Ozempic, Wegovy, and Mounjaro. This consolidation is a procedural step and does not constitute a finding that the medications caused the condition.