Semaglutide is the active ingredient in the popular weight-loss drugs Ozempic and Wegovy, which help control appetite and regulate blood glucose levels and whose use in the treatment of obesity should be combined with a healthy diet and physical exercise. These novel weight-loss drugs were considered by Science magazine as the main scientific advance of 2023. However, a new study has linked semaglutide to a serious eye disease that can lead to blindness and is known as non-arteritic anterior ischemic optic neuropathy, or NAION.
The study, led by researchers at Mass Eye and Ear, found that patients with diabetes who were prescribed semaglutide were more than four times more likely to be diagnosed with NAION, while overweight or obese people who were prescribed it were more than seven times more likely to be diagnosed.
“The use of these medications has skyrocketed in 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,” said Dr. Joseph Rizzo, director of the Neuro-Ophthalmology Service at Mass Eye and Ear and the Simmons Lessell Professor of Ophthalmology at Harvard Medical School and corresponding author of the study. “It is important to note, however, that the increased risk is associated with a disorder that is relatively rare.”
The results of the study were published in JAMA Ophthalmology and show that the rate of non-arteritic anterior ischemic optic neuropathy, or NAION, was 8.9% in patients taking semaglutide to treat type 2 diabetes, compared with 1.8% in patients taking other types of diabetes medications.
A rare eye disease associated with semaglutide
Non-arteritic anterior ischemic optic neuropathy or NAION is relatively rare, estimated to affect around 10 in every 100,000 people in the general population. It is the second leading cause of blindness from optic nerve damage (second only to glaucoma) and the most common cause of sudden blindness from optic nerve damage.
NAION is thought to be caused by a reduction in blood flow to the optic nerve head, resulting in permanent vision loss in one eye. As Dr Rizzo explained, NAION is painless, the vision loss it causes may progress over several days before stabilizing, and the affected person has little chance of improvement as there are currently no effective treatments for the condition.
Overweight or obese people prescribed semaglutide were more than seven times more likely to be diagnosed with non-arteritic anterior ischemic optic neuropathy
Researchers analyzed data from more than 17,000 Mass Eye and Ear patients treated in the six years since Ozempic was launched, dividing patients into those diagnosed with diabetes or those who were overweight or obese. They compared patients who had been prescribed semaglutide with those taking other diabetes or weight-loss medications. They then looked at the rate of NAION diagnoses in the two groups, which revealed a significant increase in risk.
There are several limitations to the study. Mass Eye and Ear treats an unusually high number of people with rare eye diseases, the study population is mostly white, and the number of NAION cases seen over the six-year study period is relatively small. With a small number of cases, statistics can change quickly, Rizzo cautions.
The researchers also couldn’t determine whether the patients actually took their medication or whether they started taking it and then stopped taking semaglutide at some point and how this might have influenced their risk. Also, it’s important to note that the study doesn’t prove a cause-and-effect relationship, and the researchers don’t know why or how this association occurred, or why there was a reported difference in the diabetic and overweight groups.
“Our findings should be considered significant, but provisional, as future studies are needed to examine these questions in a much larger and more diverse population,” Rizzo said. “This is information we didn’t have before and should be included in discussions between patients and their physicians, especially if patients have other known optic nerve problems such as glaucoma, or if there is significant pre-existing visual loss from other causes.”
