Researchers say they have uncovered a link between semaglutide — the active ingredient in Ozempic and Wegovy — and sudden vision loss. The risk of developing nonarteritic anterior ischemic optic neuropathy (NAION) is four times higher for diabetics on semaglutide and seven times higher for people taking the drug to lose weight , according to a new study from Massachusetts Eye and Ear, a teaching hospital of Harvard Medical School. A relatively rare condition, NAION is believed to be caused by insufficient blood flow to the optic nerve head.

The result is painless but irreversible vision loss in one eye. There are no effective treatments for NAION. NAION is not fully understood — and neither is the purported relationship between semaglutide and the optic nerve disorder.

“This study is the first, to our knowledge, to report an association between semaglutide and NAION, although the design of our study did not enable query into a causal relationship between the two,” the researchers wrote in their findings, published Wednesday in the journal JAMA Ophthalmology . The investigation began late last summer when Mass Eye and Ear neuro-ophthalmologists noticed that three patients in their practice had been diagnosed with the disease in just one week. All three were taking semaglutide.

The researchers pored over the records of more than 17,000 Mass Eye and Ear patients treated in the six years since Ozempic was released and analyzed the rate of NAION diagnoses. They identifie.