A significant study has unveiled troubling findings regarding the weight-loss drug Wegovy, revealing that users of this medication face nearly five times the likelihood of experiencing sudden vision loss compared to those taking its diabetes counterpart, Ozempic. This alarming association, tied to a specific type of optic nerve incident known as non-arteritic anterior ischemic optic neuropathy (Naion), has raised critical questions about the safety profile of medications containing the active ingredient semaglutide.
The Study’s Findings
Published in the British Journal of Ophthalmology, the research examined data from the US Food and Drug Administration’s adverse event reporting system, covering reports from December 2017 to December 2024. The study specifically focused on the incidence of Naion among patients using semaglutide formulations—Wegovy, Ozempic, and Rybelsus—as well as tirzepatide (Mounjaro).
The results indicated a stark difference in risk levels. Wegovy users were found to have a fivefold increased risk of experiencing Naion compared to those on Ozempic. Notably, men were reported to be at a three times greater risk than women. This condition, often referred to as an “eye stroke,” leads to sudden and typically irreversible vision loss due to inadequate blood flow to the optic nerve.
Understanding the Risks
While the occurrence of Naion is classified as rare—affecting approximately one in 10,000 semaglutide users—the study authors highlighted a concerning “potential dose-dependent safety concern.” The variations in drug formulation and dosage between Wegovy and Ozempic may help explain the heightened risk associated with Wegovy. Dr Edward Margolin from the University of Toronto, a co-author of the study, suggested that the rapid and pronounced weight loss often facilitated by Wegovy could exacerbate the risk of Naion.
The study compared adverse event reports from those taking up to 2mg of weekly Ozempic for type 2 diabetes, 2.4mg of Wegovy for obesity, and daily doses of Rybelsus. Notably, the research did not find any increased risk associated with Rybelsus or Mounjaro, attributing this to the slower absorption and uptake of these medications.
Regulatory Responses and Ongoing Concerns
These findings have prompted regulatory bodies to issue safety updates regarding the potential risks linked to semaglutide. The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) released a warning in February, echoing similar concerns from the European medicines regulator. Dr Alison Cave, the chief safety officer at MHRA, reassured the public that while the risk of Naion remains exceedingly low, it is essential for both patients and healthcare providers to remain vigilant regarding potential symptoms.
Samantha Mann, a consultant ophthalmologist at the Royal College of Ophthalmologists, emphasised that the study’s reliance on reported side effects does not definitively establish causation. She noted that instances of optic nerve strokes have not been widely reported in clinical settings, suggesting that further research is necessary to fully understand the implications of these findings.
In response to the study, Novo Nordisk, the manufacturer of semaglutide products, stated that patient safety is their paramount concern. They affirmed their commitment to closely monitoring adverse event reports and collaborating with health authorities globally to ensure the ongoing safety of their medications. Although the company acknowledged the update to patient leaflets regarding Naion, they maintained that the overall evidence does not support a causal relationship between semaglutide and the condition.
Why it Matters
The implications of this study extend far beyond individual patient experiences, highlighting the urgent need for comprehensive safety evaluations of weight-loss and diabetes medications. As the global prevalence of obesity and diabetes continues to rise, the findings surrounding Wegovy necessitate a careful reassessment of treatment strategies. Patients and healthcare providers alike must weigh the benefits of these medications against potential risks, ensuring informed decisions that prioritise long-term health outcomes. The dialogue surrounding these medications is crucial to safeguarding public health and fostering trust in pharmaceutical interventions as we navigate an increasingly complex landscape of weight management and chronic disease treatment.
