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.

In a 2024 referral-center study, semaglutide was associated with higher NAION rates in two matched cohorts: HR 4.28 among patients with type 2 diabetes and HR 7.64 among patients with overweight or obesity. A later population-based type 2 diabetes claims study compared 482,912 matched GLP-1RA and SGLT2i initiator pairs and found HR 1.85 overall; a semaglutide sensitivity analysis found HR 1.80. Both absolute rates were low in the population-based analysis. In large population data, the number of NAION events was small, which is why the right word is signal, not certainty.