Wegovy NAION Risk Is Five Times Higher Than Ozempic
A British Journal of Ophthalmology study found Wegovy associated with nearly 5x higher odds of ischemic optic neuropathy than Ozempic despite identical active ingredient.
May 26, 2026 · 3 min read
A new study published in the British Journal of Ophthalmology found that Wegovy (semaglutide 2.4 mg for weight management) is associated with nearly five times the odds of ischemic optic neuropathy — an "eye stroke" that can cause sudden, permanent vision loss — compared with Ozempic (semaglutide for diabetes), even though both drugs contain identical active ingredients at different doses.
What happened
Researchers from the University of Ottawa and the University of Toronto analyzed reports submitted to the FDA's Adverse Event Reporting System (FAERS) between December 2017 and December 2024. The study, titled "Ischemic optic neuropathy with semaglutide: global observational analysis of sex- and formulation-specific risk," focused on reports of ischemic optic neuropathy (ION), which includes NAION (non-arteritic anterior ischemic optic neuropathy).
The findings showed a strikingly different risk signal between Wegovy and Ozempic despite their shared active compound:
| Drug | Reports of ION | Adjusted reporting odds |
|---|---|---|
| Wegovy | 28 | ~75 |
| Ozempic | 47 | ~19 |
Ozempic had more total reports (47 vs. 28), but because Ozempic's user base is far larger, the adjusted odds ratio — which accounts for reporting volume — was roughly five times lower than Wegovy's. The researchers found the risk signal was more than three times stronger in men than in women, with Wegovy in male patients showing the highest adjusted reporting odds of any subgroup analyzed.
Why it matters
The finding raises an important pharmacological question: why would the same molecule at a higher dose produce a substantially different adverse-event signal, rather than a proportionally higher one? The researchers suggest several mechanisms worth investigating — higher doses may cause greater reductions in blood pressure (known to reduce perfusion to the optic nerve), greater volume depletion, or autonomic nervous system disruption. None of these are confirmed mechanisms; this is a signal-generating study, not a causal proof.
Context matters here. FAERS data has well-known limitations — reporting is voluntary, inconsistent, and subject to media-driven spikes ("notoriety bias") after a side effect is publicized. NAION was first linked to semaglutide in a 2024 case series and received significant media attention; subsequent FAERS reports may overrepresent the signal relative to true incidence.
The European Medicines Agency moved in June 2025 to classify NAION as a "very rare" side effect of semaglutide and required label updates for Ozempic, Wegovy, and Rybelsus across the EU. "Very rare" in EMA terminology means fewer than 1 in 10,000 users. The FDA has not issued equivalent label guidance as of this writing.
If you're using Wegovy and experience sudden changes in vision, particularly one-sided partial or complete vision loss, the guidance from ophthalmologists is to treat it as an emergency. Recovery of vision after NAION is limited and time-sensitive. See semaglutide side effects timeline for context on how other adverse events are classified and monitored.
What to watch
This is a pharmacovigilance signal, not a clinical trial result. What's needed — and what doesn't yet exist — is a well-designed, population-based epidemiological study controlling for cardiovascular risk factors, diabetes status, and medication co-use. The FAERS methodology cannot distinguish between patients who developed ION because of Wegovy and those who developed it coincidentally.
Prescribers and patients with pre-existing optic nerve vulnerabilities (glaucoma, history of one NAION episode, known small "cup-to-disc ratio") should discuss the risk with an ophthalmologist before starting semaglutide at weight-management doses. For the general population, the absolute risk remains low — the condition is rare, and millions of patients use these drugs without visual complications.
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