Study Finds Link Between Popular Weight-Loss Drug and Rare ‘Eye Stroke’

Although evidence is conflicting, the possible ocular side effects of using drugs such as semaglutide bear further investigation.

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A potential, although modest, increase in the risk of a rare eye condition sometimes called “eye stroke” was found in patients with Type 2 diabetes who use semaglutide, also used for weight loss, new research has found.

The authors of the new study stated, “In the absence of a known mechanism for this association, we urge clinicians to weigh the concern for an increased risk of a rare but potentially blinding eye condition with the many therapeutic benefits of semaglutide.”

Sudden Vision Loss

The condition, called non-arteritic anterior ischemic optic neuropathy (NAION), occurs when blood flow to the optic nerve is blocked, potentially causing sudden vision loss, hence the term “eye stroke.”

Although rare, it is still the most common cause of blindness among adults older than 50, with up to 10 per 100,000 people affected per year, Drs. Joseph F. Rizzo III and Jimena Tatiana Hathaway said in an invited commentary accompanying the new study published in JAMA Ophthalmology.

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Given the popularity of semaglutide medications, many researchers are studying their long-term effects.

Semaglutide is a glucagon-like peptide-1 receptor agonist (GLP-1 RA), a drug class commonly used to help control blood sugar levels in people with Type 2 diabetes.

Some research suggests that rapid reductions in blood sugar levels induced by these medications might adversely affect the optic nerve’s blood supply, leading to NAION, Dr. Meenal Agarwal, who has a doctorate in optometry, told The Epoch Times.

“However, a direct causal link has not been definitively established, and further research is necessary to understand this relationship fully,” Agarwal, who owns three vision clinics in Ontario, Canada, said.

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The researchers analyzed the data of more than 37 million adults with Type 2 diabetes from 14 different databases, including medical claims and electronic health records. The findings showed the incidence rate of NAION was 14.5 per 100,000 semaglutide users.

Researchers used two different methods to analyze the data. One compared new semaglutide users to those taking other diabetes drugs. The other compared an individual’s risk of NAION during periods when taking semaglutide with risk during times of not taking it.

Both methods found that semaglutide users had a higher risk of NAION.

No consistent risk was observed with dulaglutide, another GLP-1 RA used to control Type 2 diabetes, although the authors noted that a small signal was detected with exenatide (Byetta).

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In their commentary, Rizzo and Hathaway noted that these results contrast with other studies that reported no significant increase in the risk of NAION from semaglutide or any GLP-1 RA. They said semaglutide “may not be associated with an increased risk of NAION in the general population.” They did not provide an explanation for the difference in results.

Further Evidence Needed

The findings suggest “a modest increase in the risk of NAION among individuals with [Type 2 diabetes] associated with semaglutide use, smaller than that previously reported,” the study authors wrote, noting that this warrants further investigation into ophthalmic risk factors and the effects of different dosages.

Previous studies have offered conflicting evidence for a link between semaglutide and the potentially blinding eye condition.

In their commentary, Rizzo and Hathaway said their own previous research may have presented an exaggerated risk.

But they pointed to another study that could have underestimated NAION risk because of several factors, including a greater likelihood of misdiagnoses by doctors who are not eye specialists; lack of a specific diagnostic code for NAION; and the fact that some of the data sources did not include individuals aged 65 years or older, who are “the people most likely to develop NAION,” according to Rizzo and Hathaway.

Novo Nordisk’s Response

In an emailed statement, a spokesperson for drugmaker Novo Nordisk, which manufactures different semaglutide medications, told The Epoch Times that the company had conducted an analysis across randomized controlled clinical trials with GLP-1 RA drugs that included a blinded ophthalmologist evaluation to confirm NAION diagnoses.

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Through this analysis, the spokesperson said, very few ophthalmologist-confirmed NAION cases were found, “with no imbalance disfavoring Novo Nordisk GLP-1 receptor agonists.”

Agarwal emphasized that there are yet no definite answers about a direct causal link between semaglutide and NAION, but that “educating ... patients about possible ocular side effects of using GLP-1 receptor agonists is crucial.”

If patients experience any sudden changes in vision, typically without pain, while on these medications, she advised that they visit their eye doctor as soon as possible.

“Early detection and management are vital to prevent potential long-term visual loss,” she said.