Hundreds of consumers are suing manufacturers of GLP-1 receptor agonists, alleging that the medications may increase the risk of a rare form of vision loss. The patients contend that the drugs caused nonarteritic anterior ischemic optic neuropathy, known as NAION, according to The Wall Street Journal.

NAION occurs when blood flow to the optic nerve is suddenly reduced, resulting in abrupt vision loss. The American Academy of Ophthalmology and the National Eye Institute describe the condition as an “eye stroke.”

The condition is the most common cause of acute optic nerve injury among adults older than 50. Dr. Douglas Lazzaro, an ophthalmologist at NYU Langone Health, warned that the damage can be severe and difficult to address.

“The problem with NAION is there's no treatment,” Lazzaro told Fox News Digital. “So it can cause some very profound vision loss.”

The lawsuits involve Novo Nordisk, which makes Ozempic and Wegovy, and Eli Lilly, which makes Mounjaro and Zepbound. Both companies have disputed the allegations, according to The Wall Street Journal report.

Novo Nordisk called the lawsuits meritless and cited company funded research that found no increased NAION risk associated with its drugs. Eli Lilly said it continues to monitor safety data and maintained that current studies do not prove GLP-1 medications cause the condition.

Much of the published research so far has examined semaglutide rather than tirzepatide. One analysis of data from 37 million adults was published in JAMA Ophthalmology in 2025.

Researchers in that analysis found that people using semaglutide experienced a modest increase in NAION risk compared with people taking SGLT2 inhibitors, another class of diabetes medication. The research did not establish that semaglutide caused the condition.

A 2024 Harvard Medical School study, also published in JAMA Ophthalmology, found that patients with type 2 diabetes who received semaglutide prescriptions had approximately fourfold higher relative risk of developing NAION. However, the absolute risk remained very low.

The authors of both studies noted that their research was observational and could not prove causation. They said additional evidence was needed to clarify the possible relationship between semaglutide and NAION.

The FDA is reviewing available evidence concerning a possible association between semaglutide and NAION. The agency has not concluded that semaglutide causes the condition and has not issued a safety warning for medications containing semaglutide.

The European Medicines Agency reached a different regulatory determination, concluding that there was sufficient evidence of a possible association. It recommended adding NAION as a “very rare” adverse reaction to semaglutide product information in Europe.

Lazzaro said assessing the statistical significance is difficult because studies can involve numerous variables and patients are hard to match precisely. Those variables include age, sex, obesity, hypertension and the severity of obesity.

NAION generally causes sudden and painless vision loss in one eye, according to the American Academy of Ophthalmology. Additional symptoms can include blurred or dim vision, decreased color vision and the loss of peripheral vision.

Symptoms often emerge first thing in the morning after a person wakes up. Vision loss is frequently permanent, although some patients may regain part of their vision over time.

No proven treatment can reverse the optic nerve damage caused by NAION. The condition remains rare, affecting roughly two to 10 people per 100,000 each year, depending on the population studied.

Major risk factors include age, diabetes, high blood pressure, high cholesterol, obstructive sleep apnea and smoking. Because many people taking GLP-1 medications have diabetes or obesity, underlying health factors could contribute to vision problems.

Diabetes itself is an established risk factor for NAION. That makes it difficult for observational research to separate the effects of the disease from any possible effects associated with the medication.

Doctors also consider what they call a “disc at risk,” which refers to certain characteristics of the optic disc or optic nerve. Lazzaro described this as a compact optic nerve where structures are crowded and said he would probably advise such a patient not to use semaglutide.

“My overall take on the matter is there's probably a slightly increased risk of NAION when using the semaglutides, but I think the health benefits outweigh the risks,” Lazzaro said.

Experts stressed that patients should not stop taking prescribed GLP-1 medication without first consulting their healthcare provider. For many people living with diabetes or obesity, the medications’ established health benefits may outweigh the potential risk to vision.