Lawsuits Mount Over GLP-1 Eye Risk, Though Causation Remains Unclear

As millions of Americans continue using GLP-1 medications for weight loss and diabetes, a growing body of litigation alleges these drugs cause serious harm, particularly vision loss. However, medical experts and regulators maintain that while a correlation has been observed, the exact frequency and causal link to conditions like NAION remain uncertain.

The case of Todd Engel highlights the human stakes involved. For forty years, Engel operated heavy machinery in Maryland before his doctor prescribed Ozempic, a GLP-1 drug, for diabetes in early 2023. That December, he awoke on New Year’s Eve unable to see out of his right eye. Doctors diagnosed him with NAION, a form of optic neuropathy caused by restricted blood flow to the eye. When Engel and his wife Shelley asked if Ozempic could be the cause, their physician said there was no known link at the time.

Seven months later, a study published in JAMA Ophthalmology reported higher rates of NAION among diabetic patients taking semaglutide, the active ingredient in Ozempic. By then, however, Engel had continued his treatment and lost vision in his left eye as well. Engel has since filed a lawsuit against manufacturer Novo Nordisk, arguing the company failed to warn patients and doctors about the risk.

Engel’s suit is part of two consolidated multi-district litigations alleging life-threatening or life-altering injuries from GLP-1 drugs. Jonathan Orent, a lead court-appointed attorney for these cases, represents 247 plaintiffs with NAION and over 4,000 others suffering from severe digestive issues such as pancreatitis and gallstones. Orent argues that manufacturers should update warning labels, as they have in Europe, noting that clinical trials are too small and homogenous to detect rare side effects.

In response, Novo Nordisk maintains that NAION and other serious conditions are exceedingly rare and that the lawsuits lack merit. The company pointed to subsequent research casting doubt on whether their drug causes NAION. Similarly, Eli Lilly stated it will vigorously defend against claims related to its GLP-1 brands Mounjaro and Zepbound.

The legal and medical debate centers on causation versus correlation. The American Academy of Ophthalmology and the North American Neuro-Ophthalmology Society issued a joint clarification stating that the JAMA study cannot prove the treatment caused NAION. They acknowledged a potential link but emphasized that further research is needed and currently do not recommend patients stop their medications.

Data from the FDA’s adverse event monitoring system shows more than 1,000 reports of optic neuropathy linked to GLP-1s since 2024, alongside nearly 190,000 total reports, the majority involving minor gastrointestinal issues. NPR analysis found 1,928 reports of pancreatitis in the same period. The FDA told NPR it is conducting its own assessment and will determine if regulatory action is necessary.

Experts note that reporting challenges persist. Mohammed Ali, a diabetes specialist at Emory University, explained that he does not report all adverse events because obesity and diabetes themselves increase risks for complications like gallstones, making it difficult to isolate drug-related causes. Additionally, the rise in online sales of GLP-1s without medical supervision has led to increased calls to poison control centers for side effects like vomiting, according to pharmacist Robert Miller.

For the Engel family, the uncertainty offers little comfort. Shelley Engel stated that her husband’s personality has changed since losing his sight and that updated warnings could have prevented the tragedy. “This could have been prevented, if we only knew,” she said.