WASHINGTON — The United States Food and Drug Administration (FDA) has ordered new warnings about a rare but serious eye condition to be added to the labeling of some of the world's most widely used weight-loss and diabetes medicines, telling patients and healthcare providers on Monday that the drugs may carry a potential increased risk of sudden vision loss. The medicines affected are the glucagon-like peptide-1 (GLP-1) drugs: Eli Lilly's Mounjaro and Zepbound, and Novo Nordisk's Ozempic and Wegovy. The FDA said it is requiring the new information to appear in the "warnings and precautions" section of the labeling for these drugs, alerting doctors and patients to the potential increased risk of non-arteritic anterior ischemic optic neuropathy, known as NAION. NAION is a condition in which blood flow to the front part of the optic nerve is reduced, damaging the nerve that carries visual signals from the eye to the brain. It is a common cause of sudden, painles...