A new study published in JAMA Ophthalmology has identified a potential link between the popular weight-loss and diabetes medication semaglutide and an increased risk of a rare but serious eye condition that can lead to permanent vision loss.
Researchers from Johns Hopkins University's Wilmer Eye Institute found that patients taking semaglutide—sold under brand names Ozempic and Wegovy—had a 32% higher relative risk of developing nonarteritic anterior ischemic optic neuropathy (NAION) compared to those not taking the medication.
NAION, sometimes referred to as an "eye stroke," occurs when blood vessels supplying the optic nerve become blocked, depriving the nerve of oxygen and potentially causing sudden, painless vision loss in one eye. The condition currently has no effective treatments, and vision often does not improve after onset.
Study Findings and Methodology
The research team, led by Dr. Cindy Cai, assistant professor of ophthalmology at the Wilmer Eye Institute, analyzed health records of more than 37 million people with type 2 diabetes. Of these, approximately 810,000 had been prescribed semaglutide to manage their condition.
The incidence rate of NAION among semaglutide users was just over 14 cases per 100,000 person-years. While this represents a statistically significant increase compared to non-users, the absolute risk remains relatively low.
"Semaglutide has a wealth of systemic benefits, but patients and prescribers of the medication should be aware of the association with an increased risk for NAION," Dr. Cai told Healio, a website for healthcare professionals.
The study also found that patients prescribed semaglutide did not have a significantly increased risk for NAION compared with other GLP-1 diabetes medications, suggesting this may be a class effect rather than specific to semaglutide alone.
Previous Research and Context
This is not the first study to identify this potential risk. A 2024 study from Mass Eye and Ear in Boston reported an even higher—more than fourfold—increased risk of NAION with semaglutide use. The new Johns Hopkins research provides "further evidence of an association between semaglutide and NAION but shows a smaller risk than that previously reported," according to the research team.
Last month, a separate report in the same journal detailed nine cases of U.S. patients who experienced vision loss after taking either semaglutide or tirzepatide (Mounjaro). Seven were diagnosed with NAION, though most noticed vision improvement after discontinuing the medications.
Mechanism Remains Unclear
Researchers have not yet determined exactly how semaglutide might increase NAION risk. One theory suggests that the rapid drop in blood sugar caused by GLP-1 receptor agonists could damage blood vessels in the eyes, as sudden changes in pressure may cause fluid to leak from delicate blood vessels in the retina, leading to swelling and damage.
"In the absence of a known mechanism for this association, we urge clinicians to weigh the concern for an increased risk of a rare but potentially blinding eye condition with the many therapeutic benefits of semaglutide," the researchers concluded.
Balancing Risks and Benefits
In an accompanying editorial, Dr. Joseph Rizzo, director of the neuro-ophthalmology service at Mass Eye and Ear, emphasized that the potential NAION risk should be considered alongside semaglutide's substantial benefits.
"GLP-1RA drugs have provided considerable benefit to millions of users, including an increased chance of improved management of type 2 diabetes, substantial reduction in body weight, substantially improved morbidity and mortality of major adverse cardiovascular events, and even reduced addictive behaviors," the editorial stated.
The editorial authors advised that patients should not stop taking semaglutide based solely on this risk, especially given the potential negative consequences of abruptly discontinuing treatment and the relatively low absolute risk of NAION. However, they suggested "added caution for patients taking semaglutide or those who are considering starting this medication if they have experienced visual loss from any cause."
Clinical Implications
Around half a million people in the UK and approximately 15 million in the US are currently using GLP-1 receptor agonists like semaglutide, which can help patients lose up to 20 percent of their bodyweight within months while also improving glycemic control.
Health officials in Denmark, where Ozempic manufacturer Novo Nordisk is based, are currently investigating the links between semaglutide and vision loss.
For patients and healthcare providers, this research underscores the importance of monitoring for vision changes while using these medications. Symptoms of NAION typically include sudden vision loss in one eye without pain, often noticed upon waking.
The researchers emphasized that more studies are needed to confirm the association and identify the underlying mechanisms before definitive recommendations can be made regarding screening or prevention strategies for patients using semaglutide and similar medications.
Other Known Side Effects
Like all medications, GLP-1 receptor agonists are associated with various side effects. Common ones include gastrointestinal issues such as nausea, vomiting, constipation, and stomach pain. Other reported problems include fatigue, headaches, dizziness, and in some cases, hair loss.
The potential vision risk adds to the growing body of knowledge about these widely used medications, highlighting the need for continued vigilance and research as their use continues to expand globally for both diabetes management and weight loss.
