For people who already have retinopathy, rapid improvements in blood sugar can transiently worsen the eye disease. That's a property of how fast blood sugar changes, not specific to these peptides, and the label for some products acknowledges it.

The second topic is a rare optic-nerve event called non-arteritic anterior ischemic optic neuropathy (NAION), a sudden vision loss tied to changes in blood flow to the optic nerve.

A 2024 eye-disease study at a major center found the rate was about 4 times higher in patients on semaglutide than in matched comparison patients. A much larger 2025 study covering about 483,000 patient pairs confirmed a signal but at a smaller size: about 1.85 times higher. Both absolute rates are low.