A recent comprehensive study published in the British Journal of Ophthalmology has revealed that patients using Wegovy—an anti-obesity medication—face nearly five times the risk of sudden sight loss compared to those taking Ozempic, a diabetes drug. This alarming finding underscores the need for heightened awareness of potential side effects associated with semaglutide, the active ingredient shared by both medications.
Understanding the Risks of Semaglutide
Semaglutide, marketed under various names including Wegovy for weight management and Ozempic for type 2 diabetes treatment, belongs to a class of drugs known as glucagon-like peptide-1 receptor agonists (GLP-1 RAs). These medications are celebrated for their ability to lower blood sugar levels, curb appetite, and promote weight loss, while also being linked to additional health advantages such as reduced risks of heart attacks and drug overdoses.
However, the new research highlights a significant safety concern. Patients on Wegovy have been found to be at a substantially elevated risk of non-arteritic anterior ischemic optic neuropathy (NAION), a condition often referred to as an “eye stroke.” NAION is characterised by sudden vision loss due to diminished blood flow to the optic nerve, and while it remains a rare side effect—affecting approximately one in 10,000 users of semaglutide—the implications are serious.
Gender Disparities in Risk
The study’s findings also reveal notable gender differences in risk levels. Men who use Wegovy are three times more likely to experience sudden vision loss compared to their female counterparts. This disparity raises questions about underlying biological factors that may contribute to the increased susceptibility among men, warranting further investigation.
Dr. Edward Margolin, an ophthalmology expert from the University of Toronto and one of the study’s authors, indicated that aggressive weight loss associated with Wegovy could exacerbate the risk of developing NAION. The study analysed adverse event reports submitted to the U.S. Food and Drug Administration from December 2017 to December 2024, comparing the incidence of NAION among various formulations of semaglutide and tirzepatide (Mounjaro).
Regulatory Response and Ongoing Monitoring
In response to these findings, the UK Medicines and Healthcare products Regulatory Agency (MHRA) issued a safety update in February, acknowledging the potential risk of NAION associated with semaglutide. This warning follows similar alerts from European regulatory bodies, highlighting a growing concern over the safety profile of these medications.
Dr. Alison Cave, chief safety officer at the MHRA, emphasised the importance of awareness regarding the symptoms of potential side effects, stating, “The risk of NAION in patients prescribed semaglutide is extremely low. However, as with all medicines, patients and prescribers need to be aware of the symptoms of potential side effects, even if the risk is very small.” This proactive stance aims to ensure timely intervention should symptoms arise.
Samantha Mann, a consultant ophthalmologist and diabetic eye screening lead at the Royal College of Ophthalmologists, cautioned that while the study provides critical insights, it primarily relies on reported side effects and does not establish a definitive causal link. She noted, “An increase in this form of optic nerve ‘stroke’ has however not been widely observed in routine clinical practice at St Thomas’ in London, where I work.”
Pharmaceutical Industry’s Stance
In light of the study, a spokesperson for Novo Nordisk reaffirmed the company’s commitment to patient safety. They stated, “Patient safety is our top priority, and we take any reports about adverse events from the use of our medicines very seriously.” The company collaborates closely with regulatory bodies to monitor the safety profiles of its products continuously. They also pointed out that updates to EU patient leaflets for Wegovy, Ozempic, and Rybelsus now include warnings about NAION.
Despite the concerning findings, Novo Nordisk maintains that the overall benefits of semaglutide outweigh the risks, asserting that the current data does not suggest a causal relationship between the medication and NAION.
Why it Matters
The implications of this study are profound, particularly within the context of increasing prescriptions for weight-loss medications like Wegovy. As public health systems grapple with the obesity epidemic, understanding the full spectrum of risks associated with these treatments is imperative. The findings highlight the necessity for ongoing vigilance among healthcare providers and patients alike, ensuring that while we strive for effective obesity management, we do not overlook the potential for serious, albeit rare, side effects that may have lasting impacts on quality of life.
