Evidence linking Ozempic, Wegovy and Mounjaro to a rare optic-nerve disorder remains limited, but regulators are urging urgent assessment after sudden vision changes.
GLP-1 injections such as Ozempic, Wegovy and Mounjaro have transformed treatment for type 2 diabetes and obesity, but they are now drawing closer scrutiny over a rare eye complication linked to sudden vision loss. Recent reporting and a growing body of research have focused attention on non-arteritic anterior ischaemic optic neuropathy, or NAION, a condition that cuts blood flow to the optic nerve and can leave lasting damage. The overall risk still appears small, yet the signal has been strong enough to prompt renewed scientific and regulatory attention.
GLP-1 medicines mimic a natural gut hormone that helps regulate blood sugar and appetite. They increase insulin release when glucose rises, suppress glucagon, slow stomach emptying and help people feel full sooner. That broad metabolic effect is one reason they have become so widely used, especially because semaglutide and tirzepatide can produce substantial improvements in weight and glucose control. The same patient groups that benefit most from these drugs often already have diabetes, high blood pressure or other vascular risk factors, which complicates efforts to separate the medicine from the underlying disease.
NAION is different from many common eye problems because it typically arrives suddenly, without pain, and most often affects one eye. People may wake up with blurred vision, a darkened area in their sight or colours that appear faded. In many cases, the damage is permanent. The condition is more likely in people over 50, particularly those with diabetes, sleep apnoea, high cholesterol, smoking history or a crowded optic disc, an anatomical feature that can leave the nerve more vulnerable to restricted blood supply.
The concern around semaglutide emerged in 2024, when researchers at Mass Eye and Ear in Boston reported an elevated rate of NAION among patients using the drug. Subsequent population studies, including work from Denmark and other registry-based analyses, suggested the association may be real, though the number of cases remains very small. More recent work has extended the question to tirzepatide as well, with a 2026 study from Rutgers University reporting a similarly low but measurable increase in cases among adults with type 2 diabetes.
Regulators have responded cautiously. The European Medicines Agency’s safety committee concluded that NAION should be listed as a very rare adverse effect of semaglutide, and UK medicines officials have updated product information to advise urgent eye assessment if sudden vision changes occur. Even so, experts continue to stress that the absolute risk is low and that the evidence does not yet prove a direct causal link. Several analyses have not found a statistically significant increase, and researchers have warned that observed differences could still reflect patients’ pre-existing health risks rather than the drugs themselves.
For patients, the practical message is not to stop treatment abruptly, but to treat sudden vision change as an emergency. Anyone taking a GLP-1 medicine who develops one-sided blurring, darkening or loss of part of the visual field should seek same-day ophthalmic assessment and tell the clinician exactly which medicine they are using. Doctors may advise stopping semaglutide if NAION is confirmed, but that decision should be made medically, not by patients on their own. For people starting treatment, especially those with diabetes or known eye disease, a baseline eye examination and regular follow-up can help spot problems early while preserving the broader benefits these medicines can offer.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
