A US adverse-event database showed a much stronger reporting signal for ischemic optic neuropathy among reports naming Wegovy than among those naming Ozempic. That is a reason for further study, not evidence that every Wegovy user faces five times the risk of sudden blindness.
The study, published in the British Journal of Ophthalmology, compared disproportionate reporting across semaglutide products. Its headline figure described the relative strength of signals in a spontaneous-report system. It did not compare Wegovy users with untreated people, count all exposed patients or calculate an individual's chance of harm.
What the Fivefold Figure Actually Compared
Researchers examined the US Food and Drug Administration's Adverse Event Reporting System from December 2017 through December 2024. After deduplication, they identified 31,774 reports in which semaglutide was the primary suspect drug, including 3,070 reports for Wegovy and 20,608 for Ozempic.
There were 28 ischemic optic neuropathy reports associated with Wegovy and 47 associated with Ozempic. The reporting odds ratio was 74.89 for Wegovy and 18.81 for Ozempic when each product was compared with the rest of the database. The study's nearly fivefold comparison came from the difference between those reporting signals.
A reporting odds ratio is not a relative risk or incidence rate. It asks whether a particular event appears more often than expected among reports for a drug. The database has no reliable denominator for the total number of people using each product, and submission of a report does not prove that the medicine caused the event.
Ozempic also had roughly seven times as many total reports as Wegovy, partly reflecting its earlier launch and broader use. Raw case counts and disproportionality estimates answer different questions. Neither shows that Wegovy caused blindness in a defined percentage of patients.
The Study Found a Signal, Not a Causal Verdict
The eye condition at issue is non-arteritic anterior ischemic optic neuropathy, or NAION. It occurs when blood flow to the optic nerve is reduced and can cause sudden, usually painless loss or blurring of vision, often in one eye.
The authors proposed that dose or formulation differences might help explain the stronger Wegovy signal. Wegovy is licensed at a higher maximum weekly dose than Ozempic. But the analysis did not measure the dose taken by every patient or establish a biological mechanism linking a particular formulation to an event.
The limitations are substantial. Spontaneous reports can be incomplete, duplicated, stimulated by publicity or shaped by differences in prescribing and patient populations. The researchers could not fully adjust for diabetes, hypertension, sleep apnoea, smoking, high cholesterol or other factors associated with NAION. They also lacked consistent clinical confirmation and severity data.
Those weaknesses do not make the signal meaningless. They define what it can support: a request for prospective studies and closer surveillance. They do not support the old article's claim that Wegovy users generally face a fivefold risk of sudden blindness.
Regulators Describe the Absolute Risk as Very Rare
The UK's Medicines and Healthcare products Regulatory Agency updated semaglutide product information in February 2026 after a European review. It said the available evidence suggested approximately twice the relative risk of NAION with semaglutide and estimated about one additional affected person per 10,000 treated each year.
The regulator therefore lists NAION as a very rare possible side effect, meaning it may affect up to one in 10,000 people taking semaglutide. That estimate covers the medicine across its authorised brands and comes from a broader regulatory assessment, not from converting the new database signal into an incidence rate.
The MHRA had received three UK spontaneous reports linked to semaglutide through August 1, 2025, while approximately 10.2 million packs had been dispensed. It cautioned that a report does not establish causation and that the number of packs is not the number of treated patients.
Underlying risk also matters. Type 2 diabetes itself is associated with NAION, as are smoking, high blood pressure and high cholesterol. A fair assessment must separate a possible drug contribution from the conditions for which semaglutide is often prescribed.
The Practical Warning Must Stay Precise
Patients who experience sudden loss of sight or rapidly worsening vision should seek urgent help from an eye casualty service or emergency department, according to the MHRA. NAION is commonly painless, so waiting for eye pain would be the wrong threshold for action.
The regulator tells clinicians to stop semaglutide if an ophthalmologist confirms NAION. That is a clinical instruction after assessment, not a reason for patients without a diagnosis to change treatment on their own. Questions about continuing, switching or stopping the medicine belong with the prescriber who can weigh metabolic benefit against individual risk.
The hard lesson is about the difference between surveillance and certainty. A powerful signal in a reporting database deserves investigation, transparent labelling and usable emergency advice. Turning it into a fivefold personal-risk claim erases the denominator, the comparator and the study's limitations.
That exaggeration can harm in two directions: it can create unmanaged treatment changes, or make later corrections sound like industry reassurance. The defensible position is stricter. Regulators and manufacturers should keep testing the signal with data that can measure incidence, while headlines must state plainly that this study compared Wegovy reports with Ozempic reports and did not prove that either drug caused the cases.