Ozempic, Wegovy and similar drugs are, without a doubt, revolutionising medicine. They have transformed our ability to manage obesity and type 2 diabetes, but have actually shown potential for a wide range of conditions, such as Alzheimer鈥檚 disease, addiction and depression.
Yet, as our understanding of the benefits of these drugs grows, so too does our knowledge about their potential side effects, one of which appears to be a rare type of vision loss called non-arteritic anterior ischemic optic neuropathy (NAION).
NAION occurs when insufficient blood flow damages the bundle of nerves that connect the brain to the back of the eye, causing sudden and permanent vision loss, which most commonly includes cloudiness, blurring and dark spots, usually in one eye.
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The condition was first linked with semaglutide 鈥� the active ingredient in Ozempic and Wegovy 鈥� in 2024, when Jimena Hathaway at Harvard University and her colleagues analysed data from more than 16,800 people who had been evaluated by a neuro-ophthalmologist.
They found that among the 710 participants with type 2 diabetes, those prescribed semaglutide were as those taking other anti-diabetes medications, such as insulin or metformin. Among the 361 people prescribed semaglutide for weight issues, the risk was even greater: those given semaglutide were 7.6 times as likely to develop NAION as those receiving other weight-loss drugs, such as naltrexone or orlistat.
However, the study was limited by the fact that it only looked at people who had seen a neuro-ophthalmologist, who may have had particularly severe NAION or already been experiencing other types of vision complications.聽鈥淚 was very hesitant to trust the findings,鈥� says at the University of Southern Denmark.
So, he and his colleagues conducted an , involving more than 61,000 people who were prescribed semaglutide for type 2 diabetes. They compared them with nearly 119,000 people receiving a different class of type 2 diabetes medications, known as sodium-glucose cotransporter 2 (SGLT2) inhibitors.
After adjusting for factors such as age, sex, any underlying health conditions and diabetes severity, the researchers found that those prescribed semaglutide were almost three times as likely to develop NAION, according to their medical records. 聽鈥淲e see a very convincing and strong [signal],鈥� says Potteg氓rd.
This doesn鈥檛 mean it is a frequent side effect, however. The team also found that semaglutide is associated with only one or two additional NAION cases per 10,000 people treated each year in Denmark and Norway, where the study participants lived. 鈥淪o this is absolutely still a rare disease,鈥� says Potteg氓rd.
It isn鈥檛 entirely clear whether semaglutide is really driving this side effect. Diabetes is a for NAION, for instance. But the baseline characteristics in Potteg氓rd鈥檚聽study were similar between those taking semaglutide or other diabetes medications. In fact, semaglutide users tended to be younger, which should lower their likelihood of developing NAION, not raise it, he says.
Potteg氓rd therefore thinks that semaglutide itself is probably the cause. at the University of British Columbia in Canada says the leading explanation is that the drug brings about a rapid , which could trigger NAION. But Potteg氓rd isn鈥檛 convinced.
For one, semaglutide doesn鈥檛 cause an instantaneous drop in blood sugar, he says. 鈥淸It] is not particularly different than what the SGLT2 inhibitors would give you.鈥� He and his colleagues also didn鈥檛 find that those who developed NAION consistently did so soon after starting the drug, which is what you would expect if a rapid drop in blood sugar is to blame. 鈥淪o there are some thoughts as to mechanism, but nothing proven and also nothing particularly convincing,鈥� says Potteg氓rd.
At this point, there are also no warning signs that may indicate whether someone has a higher likelihood of developing NAION on semaglutide. That is why more data is needed, especially in diverse populations. 鈥淎s with most healthcare research, we now have data on white individuals, and we probably should be careful extrapolating whether the risk is the same for Black or Asian communities,鈥� says Potteg氓rd.
Perhaps reassuringly, there is a very small risk of developing NAION while taking semaglutide, so it probably won鈥檛 guide prescription decisions, unless someone is already experiencing some form of vision loss, says Potteg氓rd. Still, it is important to discuss any concerns you may have with your doctor, says Sodhi. 鈥淕iven that millions of people are taking these drugs, even with rare side effects, that can [amount] to anywhere from tens of thousands to even potentially hundreds of thousands of people who could be at risk,鈥� he says.
