The condition, called ischemic optic neuropathy (ION), occurs when blood flow to the optic nerve is reduced or blocked. This can cause sudden partial or complete blindness in one or both eyes.

Researchers reported that Wegovy showed the strongest association with ION among semaglutide based GLP-1 drugs analyzed in the study, which was published in the British Journal of Ophthalmology. The findings also suggested the risk signal was nearly five times stronger for Wegovy than for Ozempic.

Although the condition appears to be rare, the researchers say the findings raise important safety questions as the use of GLP-1 medications continues to expand worldwide.

FDA Safety Reports Analyzed

To investigate the potential connection, researchers reviewed reports submitted to the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) between December 2017 and December 2024.

The database contains reports of unintended and harmful side effects linked to medications. In total, the researchers examined more than 30.6 million adverse event reports.

Among those, 31,774 involved semaglutide drugs. The average age of people in the reports was 56, and 54% were women.

The analysis focused on several GLP-1 medications, including injectable Ozempic for type 2 diabetes, injectable Wegovy for obesity treatment, and the oral semaglutide tablet Rybelsus. Researchers also evaluated tirzepatide drugs, including Mounjaro and Zepbound.

Wegovy Showed the Strongest Signal

Although Ozempic generated far more reports overall because it was approved earlier, Wegovy showed the strongest association with ION.

Researchers identified 28 reports of ION linked to Wegovy and 47 linked to Ozempic. Despite the lower number of reports, the statistical signal for Wegovy was much stronger, with odds nearly 75 times higher than expected. Ozempic showed odds of nearly 19, while generic semaglutide products showed odds of 21.

No cases of ION were reported for Rybelsus, the oral tablet version of semaglutide.

The study also found major differences between men and women. Men using Wegovy showed the highest signal overall, with odds 116 times higher than expected. Among women, the strongest signal appeared with Ozempic.

Further analysis suggested the odds of ION were more than three times higher in men than in women.

Why Researchers Think Wegovy May Differ

The researchers believe several factors could explain the stronger signal seen with Wegovy.

Injectable drugs tend to act faster than oral medications, and Wegovy is prescribed at a higher dose than Ozempic. The authors suggested that high dose Wegovy may increase the risk of reduced blood supply to the optic nerve through mechanisms involving blood pressure drops, fluid loss, and instability in the autonomic nervous system.

However, they emphasized that no direct clinical cause-and-effect relationship has been proven.

"In contrast, the limited absorption and slower uptake of Rybelsus probably explain the absence of a detectable signal," the researchers wrote.

They also noted that media attention surrounding Wegovy may have increased reporting of side effects, which could have influenced the results.

Researchers Call for Urgent Follow-Up Studies

The FDA reporting system has important limitations. It cannot determine how often the condition actually occurs, and the reports do not include detailed information about patients' health conditions or disease severity.

Even so, the researchers said the findings provide early evidence that the risk may depend on both the formulation and dose of semaglutide drugs.

"This study provides the first evidence of a formulation-and dose-dependent ION risk, with the strongest association observed for Wegovy," the researchers concluded.

"These findings highlight a potential dose-dependent safety concern that warrants urgent prospective evaluation to guide prescribing and regulatory policy."

Authors of a related commentary agreed that the findings deserve closer attention from eye specialists and researchers.

"These findings add to an emerging body of growing literature reporting ocular complications with [anti-obesity medications] which warrants further scrutiny and urgent clarification for ophthalmologists," they wrote.

Growing Use of GLP-1 Drugs Raises Concerns

The researchers noted that obesity rates remain high in many countries, particularly in the United Kingdom, where 29% of adults are obese and 64% are overweight or obese.

At the same time, GLP-1 medications are increasingly being explored for benefits beyond weight loss and diabetes treatment. Research suggests these drugs may also help reduce risks linked to cardiovascular disease, stroke, and dementia.

Because of these expanding uses, experts expect prescriptions for the medications to continue rising.

The commentary authors also pointed to growing debate around the use of anti-obesity drugs in children over age 12, warning that wider use could potentially increase the number of rare eye complications seen later in life.

At the same time, researchers noted that GLP-1 drugs may benefit some eye conditions, including age related macular degeneration and uveitis.

Still, they cautioned that these potential benefits must be weighed against the possibility of rare but serious complications such as ION.