New Research Confirms Weight-Loss Drugs Linked to Sudden Vision Loss

GLP-1 receptor agonists—including Ozempic, Wegovy, and Mounjaro (semaglutide and tirzepatide)—have revolutionized diabetes and obesity treatment by mimicking the appetite-suppressing hormone GLP-1, helping users lose weight and manage blood sugar levels. But two fresh studies reveal a small increased risk of serious eye conditions, including sudden vision loss,according to Science Alert .

What is the risk?

A rare but serious eye condition called non-arteritic anterior ischemic optic neuropathy (NAION)—often dubbed an “eye stroke”—occurs when blood flow to the optic nerve is suddenly reduced or blocked. It typically causes painless, sudden vision loss in one eye, usually noticed upon waking, and about 70% of people experience no improvement in their vision afterward. Individuals with diabetes are already at higher risk of NAION.

What did past research show?

A 2024 study found that people prescribed semaglutide for diabetes had four times greater odds of developing NAION, and those using it for weight loss had nearly eight times greater odds. In response, the European Medicines Agency designated NAION a “very rare” side effect—about a 1-in-10,000 chance—and mandated the risk be included on product labels.

What do the new studies reveal?

Two recent U.S. studies analyzed records of 159,000 to 185,000 individuals with type 2 diabetes over a two-year period:

In one, 35 people (0.04%) using semaglutide or tirzepatide developed NAION, compared to 19 people (0.02%) in the control group—indicating a more modest increase in risk than earlier data suggested.

The second study found no elevated NAION risk, though it did identify a slight increase in diabetic retinopathy among GLP-1 users. Counterintuitively, those users experienced fewer severe complications and needed less invasive treatments for retinopathy compared to those on other diabetes medications.

What does this mean for patients?

These medications continue to offer clear benefits—such as better heart and metabolic outcomes—but the new findings highlight the importance of informed decision-making. Patients with risk factors (e.g., high blood pressure, sleep apnea, anatomical crowding of the optic nerve) should discuss GLP-1 use carefully with their doctors. Regular eye exams are crucial, especially since rapid reductions in blood sugar may aggravate fragile eye blood vessels. A current five-year clinical trial involving 1,500 participants is underway to clarify long-term ocular risks.