A large-scale study has found that patients taking Wegovy for weight loss have nearly five times the risk of sudden vision loss compared to those on Ozempic for diabetes. The research, published in the British Journal of Ophthalmology, examined reports of non-arteritic anterior ischemic optic neuropathy (Naion), a condition often called an 'eye stroke' that reduces blood flow to the optic nerve, causing sudden and usually permanent vision loss.
The study analysed side-effect reports submitted to the US Food and Drug Administration between December 2017 and December 2024. It compared Naion cases associated with Ozempic (up to 2mg weekly), Wegovy (up to 2.4mg weekly), Rybelsus tablets, and tirzepatide (Mounjaro). Wegovy showed the strongest association with Naion, while no increased risk was found with Rybelsus or tirzepatide. Men were found to have three times the risk of women.
Dr Edward Margolin, from the University of Toronto and a co-author of the study, said Naion is likely a real side-effect of semaglutide, the active ingredient in Wegovy, Ozempic, and Rybelsus. He noted that faster or more aggressive weight loss could increase the risk. The authors suggested that higher doses and faster-acting injections of Wegovy may explain the stronger association, while slower absorption of Rybelsus tablets likely explains the absence of a detectable link.
The UK Medicines and Healthcare products Regulatory Agency issued a drug safety update in February warning about the risk of Naion, following similar alerts from the European medicines regulator. Dr Alison Cave, MHRA chief safety officer, emphasised that the risk is extremely low but stressed the importance of awareness among patients and prescribers. Samantha Mann, a consultant ophthalmologist at the Royal College of Ophthalmologists, noted that such cases have not been widely observed in routine clinical practice and called for further studies to clarify the risk.
A spokesperson for Novo Nordisk, the manufacturer of semaglutide, stated that patient safety is a top priority and that the company continuously monitors the safety profile of its products. While EU patient leaflets have been updated to include Naion, the company believes the benefit-risk profile of semaglutide remains favourable.
