"Suddenly, I Can't See Out of One Eye"... Unexpected Symptom of Weight-Loss Drug Also Emerges in South Korea

'Amaurosis fugax' symptoms disappeared after stopping Wegovy
"Further research needed into previously unknown optic nerve symptoms"

A case has emerged involving a South Korean patient who suddenly developed blurred vision while taking a glucagon-like peptide-1 (GLP-1) obesity treatment and whose symptoms disappeared after stopping the medication.

According to medical sources on November 13, a patient in their 50s with obesity who was being treated for diabetes and mild diabetic retinopathy at Seoul St. Mary's Hospital in July 2025 repeatedly experienced episodes in which vision in one eye went dark for about a day or two, a condition known as amaurosis. The patient was reportedly taking Wegovy, a GLP-1 obesity treatment prescribed by the hospital's Department of Endocrinology.

A case has emerged involving a South Korean patient who suddenly developed blurred vision while taking a glucagon-like peptide-1 (GLP-1) obesity treatment, with the symptoms disappearing after the medication was stopped. Getty Images

After noting reports from overseas linking Wegovy to optic nerve disorders, the medical team performed fluorescein fundus angiography, a test that uses a fluorescent dye injected into the blood vessels to image blood flow in the retina. The results showed that blood took about 1.8 times longer than normal to circulate through the retina. Tests by the Department of Cardiology ruled out the possibility that the symptoms were caused by narrowing of the carotid artery in the neck. The hospital said the patient stopped taking Wegovy in January 2026 and had not reported any symptoms since.

Kim Gihyeon, an ophthalmology professor at Seoul St. Mary's Hospital who treated the patient, said, "One case cannot establish a direct causal relationship with the medication," but added, "It is noteworthy that tests confirmed delayed blood flow in the retina and that the episodes of amaurosis, which recurred while the patient was taking the medication, disappeared after it was stopped." Professor Kim plans to report the case to the medical community. The hospital also plans to conduct follow-up tests to check whether blood flow has returned to normal.

The prognosis differs from that of non-arteritic anterior ischemic optic neuropathy (NAION), an optic nerve disorder for which the U.S. Food and Drug Administration (FDA) recently required warning language on all GLP-1 medications. However, as regulators recognize that unexpected adverse symptoms can occur, interest in the case is growing among medical professionals. Professor Kim said, "This case suggests that GLP-1 medications may cause eye-related side effects that have not yet been identified," adding, "More similar cases should be collected and further research conducted."

Research in South Korea has also found that GLP-1 medications may slow blood flow in the retina. A study by a team led by Song Hyeonbeom, a professor of pediatric ophthalmology at Seoul National University Hospital, published in the international journal Biomedicine & Pharmacotherapy in July 2026, found that a small-scale analysis of patients taking GLP-1 medications showed a tendency for retinal blood flow to slow during treatment and return to normal after the medication was stopped. Animal experiments showed the same phenomenon, along with an increase in signs of oxygen deprivation in the retina. The research team suggested that the medication may lower intracranial pressure, narrowing the space around the optic nerve and compressing retinal blood vessels.

Experts stress that patients using GLP-1 medications should regularly monitor their eye health. They should alternately cover each eye and compare how clearly they can see with each one. If vision in one eye becomes blurred, part of the visual field is obscured, or it becomes difficult to distinguish colors, they should see an ophthalmologist immediately.

On November 9, the FDA took action requiring the risk of NAION to be stated in the "Warnings and Precautions" sections for all GLP-1 medications, including Wegovy and Ozempic, as well as Mounjaro and Zepbound. The move followed an analysis of 126 clinical trials that found a higher incidence of NAION among patients receiving the medications than in control groups. In South Korea, the Ministry of Food and Drug Safety added NAION to the prescribing information for semaglutide medications on October 7, 2026.

This content was produced with the assistance of AI translation services.