Harvard study finds Ozempic linked to rare cases of vision loss

Novo Nordisk's best-selling diabetes and weight-loss drugs, Ozempic and Wegovy, appear to be associated with an increased risk of a rare form of vision loss, according to an analysis by doctors at Massachusetts Eye and Ear Infirmary, affiliated with Harvard University Hospital.

A study examining patient records found that patients who took the drug to lose weight were more than seven times more likely to be diagnosed with a stroke-like eye disease called NAION than those who took other types of obesity medications. Patients who took the diabetes drug were more than four times more likely to develop the rare condition than those taking other types of treatments, according to results published Wednesday in JAMA Ophthalmology.

The relatively small study looked at patient records at Massachusetts Eye and Ear Infirmary. The paper said the number of cases of eye disease in people who took the drug was low — 37 cases in both groups combined — limiting the study's statistical power. The findings don't prove that the drug caused the eye complications, and they need to be replicated in larger studies involving more hospitals, the Harvard researchers and other experts said.

“I don't think this is a strong enough signal to force patients off the drug,” said Susan Moran, a neuro-ophthalmologist in Birmingham, UK, who wrote an editorial about the study. The study doesn't show that the eye effects happened immediately after taking the drug — in some cases it happened months later. Still, she said, doctors should inform patients about the potential risks.

The phenomenal popularity of Novo and rival Eli Lilly's weight-loss drugs has led both companies to try to address the shortage. Novo's semaglutide, the active ingredient in Ozempic and Wegovy, has been studied for more than 15 years and scientists consider it generally safe. But as more people use the drug, researchers are looking for previously unknown side effects.

Novo's American depositary receipts were down as much as 4.9 percent as of 11:48 a.m. New York time, while Lilly's shares were down as much as 2.5 percent.

“Patient safety is a top priority for Novo Nordisk and we take all reports of adverse events resulting from the use of our medicines seriously,” a Novo spokesperson said in an emailed statement. The Harvard study had several important limitations, and other large field studies reaffirm that the medicines are safe, the spokesperson said. NAION is not included among the adverse reactions listed on the package inserts for the two medicines, the spokesperson said.

Look carefully

The Massachusetts Eye and Ear Institute analysis was designed to examine whether semaglutide was associated with an increased risk of NAION after doctors noticed several cases and patients taking the drug. The disease typically affects 1 in 10,000 to 50,000 people per year and typically leads to partial vision loss in the affected eye. There is no standard treatment.

This potential risk “is definitely something that should be looked at more carefully,” said Mahyar Etminan, a drug-safety researcher at the University of British Columbia in Vancouver, who was not involved in the study. “This is a very serious condition, so if this is true, it changes the risk-benefit calculation.”

This is especially true for people who are taking Wegoby solely for weight loss and have no other medical conditions that could benefit from the treatment, he added.

It's hard to know

Etminan said there are other reasons he thinks it's important to continue this study. It's unclear how Ozempic or Wegovi cause the eye disease, he noted, because diabetes itself is a risk factor for eye disease. The design of the studies makes it hard to know whether it was the severity of their diabetes or heart disease, rather than taking the drugs, that put patients at higher risk, he said.

The study included 710 patients prescribed diabetes medications and 979 patients prescribed weight-loss medications who were treated at Massachusetts Eye & Ear, Nose, and Throat Hospital over a six-year period beginning in December 2017, when Ozempic was first approved. Within these two groups, the researchers compared the rates of NAION in people who received their first prescription for Ozempic or Wegovy with rates in people who received competing treatments. They did not look at Maunjaro and Zepbound, diabetes and obesity medications made by Lilly.

According to Joseph Rizzo, director of the Neuro-Ophthalmology Service at Massachusetts Eye and Ear Infirmary and professor at Harvard Medical School, the researchers began their study last summer after three patients with NAION came to their clinic over a short period of time, all of whom were taking semaglutide.

His group is now in discussions with other researchers about doing a larger study that would involve other hospitals.

“We hope that physicians and patients will be aware of this association,” he said, emphasizing that the study does not prove a causal relationship between the drug and eye disease. It is especially important for patients who already have poor vision to know about the possible risks so they can make an informed decision before starting treatment, he said.

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