Popular weight-loss drugs face numerous lawsuits over rare ‘eye stroke’ linked to vision loss

Hundreds of consumers are suing the manufacturers of GLP-1 receptor agonists, alleging the medications may increase the risk of a rare form of vision loss.

The patients behind the lawsuits allege that the medications caused NAION (nonarteritic anterior ischemic optic neuropathy), according to The Wall Street Journal.

NAION is a rare eye condition in which blood flow to the optic nerve is suddenly reduced, leading to sudden vision loss.

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It is the most common cause of acute optic nerve injury in adults over age 50, according to the American Academy of Ophthalmology and the National Eye Institute, which describes it as an "eye stroke."

"The problem with NAION is there's no treatment," Dr. Douglas Lazzaro, an ophthalmologist at NYU Langone Health, told Fox News Digital. "So it can cause some very profound vision loss."

The companies in question, Novo Nordisk (maker of Ozempic and Wegovy) and Eli Lilly (maker of Mounjaro and Zepbound), have disputed the allegations, according to the WSJ report.

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Novo Nordisk called the lawsuits meritless and pointed to company-funded research finding no increased risk of NAION 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.

Fox News Digital reached out to the companies requesting comment.

Most of the published research to date has examined semaglutide, rather than tirzepatide.

In a data analysis of 37 million adults published in JAMA Ophthalmology in 2025, researchers found that people using semaglutide experienced a modest increase in NAION risk compared to people taking SGLT2 inhibitors, another class of diabetes medication.

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A 2024 Harvard Medical School study, published in the same journal, found that patients with type 2 diabetes who were prescribed semaglutide had approximately a fourfold higher relative risk of developing NAION. The absolute risk remained very low.

The authors of both studies noted that the research was observational and could not prove that the medication caused NAION. They emphasized that more evidence is needed.

The FDA has said it is reviewing available evidence regarding a possible association between semaglutide and NAION. The agency has not concluded that semaglutide causes NAION and has not issued a safety warning for semaglutide medications.

The European Medicines Agency concluded there is sufficient evidence of a possible association to recommend adding NAION as a "very rare" adverse reaction to semaglutide product information in Europe.

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Lazzaro agreed that "whether or not that's statistically significant is hard to assess, because there were so many variables in this and it's hard to exactly match patients."

"But when they removed all of what they felt were confounding variables… how obese were the patients, male versus female, age, hypertension, level of obesity… they did find that there was a higher risk of NAION."

NAION typically causes sudden, painless vision loss in one eye, per the AAO. Other symptoms may include blurred or dim vision, loss of peripheral vision or decreased color vision.

Symptoms tend to develop first thing in the morning after waking up.

The biggest risk factors for the condition include age, diabetes, high blood pressure, high cholesterol, obstructive sleep apnea and smoking. As many people taking GLP-1 drugs have diabetes or obesity, some of these underlying risk factors could be factors in vision issues, experts note.

Diabetes itself is a well-established risk factor for NAION, making it difficult for observational studies to separate the effects of the disease from those of the medication, experts have noted.

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Vision loss from NAION is often permanent. While some patients may regain partial vision over time, there is no proven treatment that can reverse the optic nerve damage.

The condition is rare, with roughly two to 10 cases per 100,000 people each year, depending on the population studied.

Experts emphasize that patients should not stop taking a prescribed GLP-1 medication without first speaking with their healthcare provider. For many people with diabetes or obesity, the medications' proven benefits may outweigh any potential vision risk.

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When discussing NAION, one important factor is what doctors call a "disc at risk," referring to certain characteristics of the optic disc, or optic nerve.

"So if I had a patient who had what I would see on exam is a disk at risk, a very compact optic nerve where everything's crowded, I would tell that patient probably to not go on a semaglutide," Lazzaro advised.

"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," he went on. 

"And unless I have a patient with a disk at risk, I would probably tell them to go on them if they're going to be a lot healthier from an overall standpoint."