People taking weight-loss and diabetes injection drugs like Ozempic and Wegovy may have an increased risk of sudden and irreversible vision loss and blindness, a new study has found.
However, doctors say there’s no reason for patients who take the uber popular drugs to panic or discontinue taking their prescriptions.
The study, conducted by Harvard researchers and published Wednesday in JAMA Ophthalmology, analyzed data from 16,827 patients over a six-year period at the Mass Eye and Ear Harvard teaching hospital.
Of those, 710 had type 2 diabetes, with 194 being prescribed semaglutide medications, marketed under brandnames like Wegovy and Ozempic, that belong to a class of medications known as GLP-1 receptor agonists.
Another 975 patients in the study were overweight or living with obesity, 361 of them being prescribed semaglutide.
Among those prescribed semaglutide, an eye problem known as nonarteritic anterior ischemic optic neuropathy, or NAION, was eventually diagnosed in a small percentage of patients. None of the more than 16,000 patients were initially diagnosed with NAION.
After taking patients’ other risk factors for the condition into account, such as high blood pressure and obstructive sleep apnea, use of semaglutide was associated with a more than four times higher risk of NAION in those receiving it for diabetes and a more than seven times higher risk in patients taking it for weight issues.
Among those taking semaglutide for type 2 diabetes, 8.9 per cent developed NAION, compared to 1.8 per cent taking non-GLP-1 medications, researchers found.
Among those prescribed semaglutide for overweight or obesity, the rate of the eye condition was 6.7 per cent, versus 0.8 per cent for those receiving other types of medications for weight reduction.
NAION affects the optic nerve, the bundle of fibres that connects to the back of the eye and carries signals to the brain allowing sight. Those with NAION have reduced or blocked blood flow and oxygen to the optic nerve – a type of painless eye stroke which can result in sudden loss of vision.
The study found that the risk of developing NAION was greatest within the first year of being prescribed semaglutide, but researchers say their findings should be viewed as “tentative” for now.
Get weekly health news
“The use of these drugs has exploded throughout industrialized countries and they have provided very significant benefits in many ways, but future discussions between a patient and their physician should include NAION as a potential risk,” lead researcher Dr. Joseph Rizzo, director of the neuro-ophthalmology at Mass Eye and Ear and a professor at Harvard Medical School, said in a news release.
“Our findings should be viewed as being significant but tentative, as future studies are needed to examine these questions in a much larger and more diverse population.”
Dr. Tom Elliott, medical director with B.C. Diabetes, told Global News that he’s already fielding emails from concerned patients about the study, and is calling the association between the drug and cause of blindness “exceedingly rare.”
“It’s not like they’re saying that Ozempic causes this problem,” he explained. “It’s just more frequent in people who are taking the drug.”
Elliott says he’s reassuring his patients that if they have good reason to be taking a semaglutide, “the benefits massively outweigh the downside,” and that the drugs can be “enormously beneficial.”
He says that not only are semaglutide drugs helpful in managing diabetes and weight, but also to cardiovascular health, and that the potential risk of NAION should not deter people from using semaglutide if they really benefit from it.
“In people with previous heart attacks and strokes, (these drugs) reduces the risk of death by 20 per cent. So, in people who haven’t had those events….the overall benefits to diabetes, to weight, to cardiovascular risk, are quite significant.”
Another factor in the study that needs to be considered, says Dr. Mark Eltis, president of the College of Optometrists of Ontario, is that leaving diabetes untreated can also cause vision problems.
“If we don’t treat diabetes, the blood vessels at the back of the eye can become leaky, or new blood vessels can form which are not as stable as the regular ones because they’re not supposed to be there, and so they can more easily collapse and cause hemorrhaging or bleeding at the back of the eye.”
While NAION is the second-most common optic nerve condition, Eltis says it’s a “far distant second” to glaucoma. What differentiates the two, however, is that NAION causes sudden vision loss, where glaucoma is usually a more gradual disease that sees vision worsen over a period of time.
Novo Nordisk, in an emailed statement to Reuters, noted several limitations of the study design, which was not a randomized controlled trial, and pointed out that the study did not take into account some potentially pertinent information such as how long patients had diabetes or whether they were smokers.
“Overall, the data published in the study is not sufficient to establish a causal association between GLP-1 receptor agonist use and NAION,” the Danish drugmaker, which manufactures Wegovy and Ozempic, said, adding that the condition “is not an adverse drug reaction for the marketed formulations of semaglutide.”
It’s worth noting that Canadian warnings for both Ozempic and Wegovy include vision changes among potential side effects.
Eltis says anyone considering taking semaglutide should speak to their doctor about the risks and benefits of the treatment and be assessed for any eye conditions at the time, too, to ensure an individualized plan.
“You cannot leave the diabetes untreated. That is not the correct path. Every treatment has a risk and benefit, and a lot of these should not be blown out of proportion because they are low probability.”
— With files from Global News’ Katherine Ward and Reuters