A peer-reviewed analysis of U.S. adverse event data has found that patients taking Wegovy face nearly five times the risk of a sudden, sight-threatening eye condition compared with those on Ozempic, despite both drugs containing the same active ingredient, semaglutide. The study, which examined reports spanning seven years, identified an adjusted odds ratio of 4.74 for ischaemic optic neuropathy among Wegovy users relative to Ozempic users. The finding sharpens a growing debate over whether the higher doses used for weight loss carry distinct vascular risks that the diabetes formulation does not.
What the FAERS Data Revealed
The study, published in the British Journal of Ophthalmology, drew on semaglutide case reports filed with the FDA Adverse Event Reporting System from December 2017 through December 2024. Researchers isolated cases of ischaemic optic neuropathy, or ION, a condition in which blood supply to the optic nerve is abruptly cut off, often causing permanent vision loss in one eye. After adjusting for confounders, Wegovy carried an adjusted odds ratio of 4.74 relative to Ozempic, a gap that persisted across sex-stratified subgroups.
That nearly fivefold difference is striking because the two drugs share identical pharmacology. The key distinction is dosing: Wegovy is approved at up to 2.4 mg weekly for weight management, while Ozempic tops out at 2 mg for type 2 diabetes. A dose-dependent vascular effect is one plausible explanation, though the study design cannot confirm causation. The analysis also reported formulation-specific and sex-stratified signals for ION, suggesting the risk may not fall evenly across patient populations.
Reporting by The Guardian underscored that, among more than 20,000 adverse event reports involving semaglutide, Wegovy accounted for a disproportionate share of sudden sight-loss cases when compared with Ozempic. While spontaneous reports cannot establish absolute risk, they reinforced the pattern seen in the formal odds-ratio analysis and raised questions about whether higher-dose regimens for obesity might carry distinct ocular hazards.
The authors relied on the FDA’s own FAERS dashboard to identify relevant cases, applying filters for semaglutide-containing products and optic nerve disorders. They then compared reporting frequencies between Wegovy and Ozempic while adjusting for age, sex, indication, and concomitant medications. Because FAERS is a voluntary reporting system, the resulting odds ratios reflect relative reporting risk rather than precise incidence rates, but they are often used to flag safety signals that merit closer epidemiological scrutiny.
Regulators Call the Risk “Very Rare”
European and international health authorities have acknowledged the signal but framed it as uncommon. The European Medicines Agency’s Pharmacovigilance Risk Assessment Committee, known as PRAC, concluded that non-arteritic anterior ischaemic optic neuropathy, or NAION, the most common form of ION, qualifies as a very rare adverse effect of semaglutide medicines, affecting up to 1 in 10,000 users. PRAC cited evidence from non-clinical studies, clinical trials, post-marketing surveillance, and epidemiological research to reach that classification.
The World Health Organization issued a separate alert in June 2025, warning health-care professionals and regulatory authorities about the NAION risk with semaglutide, while also classifying the frequency as very rare. Neither body, however, distinguished between formulations in their public statements. That gap matters: if Wegovy’s risk is nearly five times Ozempic’s, a blanket “very rare” label may obscure meaningful differences for patients prescribed the weight-loss version, particularly those without diabetes who might otherwise consider themselves at lower vascular risk.
Earlier Studies Built the Case
The new FAERS analysis did not emerge in isolation. A separate large-scale study using the Observational Health Data Sciences and Informatics network examined tens of millions of type 2 diabetes patients and reported a NAION incidence of about 14.5 per 100,000 among semaglutide users. That figure sits within the “very rare” threshold but is notably higher than background NAION rates in the general population, which typically range from 2 to 10 per 100,000 depending on age and comorbidities.
An earlier retrospective study published in JAMA Ophthalmology used matched cohorts of patients with type 2 diabetes and those with overweight or obesity, finding higher NAION rates in semaglutide-treated patients compared with carefully selected comparators in both groups. That paper helped spark the broader investigation into whether semaglutide carries a unique optic nerve threat beyond what underlying metabolic conditions alone would explain, particularly when used at doses approved for obesity.
A systematic review and meta-analysis, also published in Ophthalmology, pooled the available observational and trial data and provided indication-stratified estimates for type 2 diabetes versus obesity and overweight populations. The review included certainty-of-evidence grading, and while the overall evidence was rated low certainty, the direction of the signal was consistent across indications and study designs, with semaglutide-exposed groups showing higher NAION risk than controls in most analyses.
Why the FAERS Gap Between Formulations Matters
Most coverage of semaglutide and eye risk has treated the drug as a single entity. The new British Journal of Ophthalmology study challenges that framing by showing that the formulation prescribed for weight loss carries a disproportionate share of the reported ION cases. For the millions of non-diabetic patients using Wegovy primarily to lose weight, this distinction has practical consequences. Diabetic patients on Ozempic often have pre-existing microvascular disease, which itself raises NAION risk. The fact that Wegovy users, who may lack those baseline vascular problems, still report ION at higher rates suggests something specific to the weight-loss regimen, whether dose magnitude, speed of weight change, or an unmeasured confounder, is at play.
The FAERS-based odds ratio does not prove that Wegovy causes ION more often than Ozempic in absolute terms, but it does indicate a stronger reporting signal. Several hypotheses could explain the discrepancy. Higher peak and cumulative doses might exert greater effects on blood pressure regulation or optic nerve perfusion. Rapid weight loss could alter hemodynamics or sleep apnea severity, both of which are linked to NAION. Alternatively, prescribing patterns might differ, with Wegovy reaching younger or more visually attentive patients who are quicker to report symptoms. The current data cannot disentangle these possibilities, but they underscore that formulation and dosing are not trivial details when evaluating drug safety.
Limits of the Evidence
Experts caution that spontaneous reporting systems like FAERS are prone to under-reporting, duplicate entries, and reporting bias, especially once a potential side effect gains media attention. Patients and clinicians may be more likely to report vision problems once they are primed to look for them, which can inflate apparent risk. Conversely, many cases of NAION are never linked to medications at all, leading to underestimation. The British Journal of Ophthalmology analysis attempted to mitigate these issues with statistical adjustments and sensitivity checks, but the authors acknowledged that unmeasured confounding and incomplete data remain major limitations.
Observational cohort studies and meta-analyses face their own constraints. Even with large sample sizes and sophisticated matching, it is difficult to fully account for differences in cardiovascular risk factors, sleep apnea, or other NAION contributors between semaglutide users and controls. The “low certainty” grading in the Ophthalmology review reflects these methodological challenges. For now, the totality of evidence points to a real but numerically small increase in risk, with unresolved questions about how that risk varies by dose, indication, and individual susceptibility.
What Patients and Clinicians Can Do Now
In the absence of definitive causal proof, regulators have opted for warning language rather than sweeping restrictions. For clinicians, the emerging data argue for more explicit discussions of eye risk when initiating semaglutide, especially at higher doses. Patients should be advised to seek urgent ophthalmic evaluation if they experience sudden vision loss, dark shadows, or visual field defects, symptoms that can signal NAION and require rapid assessment to protect the unaffected eye.
Risk–benefit calculations will differ by patient. For someone with poorly controlled diabetes and high cardiovascular risk, the benefits of Ozempic in lowering glucose and reducing cardiac events may far outweigh a very small increase in NAION risk. For a relatively healthy person using Wegovy primarily for cosmetic weight loss, the calculus is more finely balanced, and alternative strategies or lower-dose regimens may deserve consideration. Shared decision-making, grounded in transparent communication about knowns and unknowns, is essential.
The new analysis also highlights a broader lesson for pharmacovigilance: identical molecules can behave differently when packaged, dosed, and prescribed in distinct clinical contexts. Treating all semaglutide products as interchangeable for safety purposes may miss formulation-specific patterns that matter to patients. As usage of GLP-1 drugs expands into ever wider populations, continued monitoring, stratified analyses, and, where feasible, prospective studies will be needed to clarify who is most at risk of rare but serious complications like sudden sight loss.
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*This article was researched with the help of AI, with human editors creating the final content.
