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.