People who have been prescribed a weight-loss injection could be at a higher risk of developing an eye condition which can lead to blindness, a study has found. The study found that people with diabetes who were prescribed semaglutide, most commonly known under the brand names Wegovy and Ozempic, were more than four times more likely to be diagnosed with an eye condition known as non-arteritic anterior ischemic optic neuropathy (naion). Naion is a disorder in which the arteries which supply blood to the optic nerve in the eye become blocked. The condition can lead to loss of eyesight due to the optic nerve being deprived of oxygen and subsequently damaged. There is no known treatment for the condition, which affects 10 out of 100,000 people in the general population. The research, published in the journal JAMA Ophthalmology and conducted by researchers at Harvard University, looked at data from 16,827 patients at the Mass Eye and Ear Harvard teaching hospital, who received treatment over a six-year period. Of the patients included within the study, 710 had type 2 diabetes, with 194 of those patients having been prescribed semaglutide. Included in the study were 975 patients who were overweight or living with obesity, with 361 of these having been prescribed semaglutide. Of the people included in the study with type 2 diabetes, 17 naion events occurred in patients who were prescribed semaglutide, compared with six who were on other diabetes drugs. Over three years, 8.9% of these people on semaglutide had naion compared with 1.8% on the other drugs, the researchers found. The study also found that people who were overweight or living with obesity who were prescribed semaglutide were more than seven times more likely to develop the condition than those on other types of weight-loss medicine. Of the people included in the study who were overweight or obese, 20 naion events occurred in people prescribed semaglutide, compared with just three events in people using other drugs. Over three years, 6.7% of these people on semaglutide had naion compared with 0.8% who were taking other weight-loss drugs. Prof Joseph Rizzo, a professor of ophthalmology at Harvard medical school, said: “Our findings should be viewed as being significant but tentative, as future studies are needed to examine these questions in a much larger and more diverse population. “This is information we did not have before and it should be included in discussions between patients and their doctors, especially if patients have other known optic nerve problems like glaucoma or if there is pre-existing significant visual loss from other causes.” Graham McGeown, honorary professor of physiology at Queen’s University Belfast, said: “This research does suggest an association between semaglutide treatment and one form of sight-threatening optic neuropathy, but this would ideally be tested in larger studies. “Given the rapid increase in semaglutide use and its possible licensing for a range of problems other than obesity and type 2 diabetes, this issue deserves further study, but possible drug side-effects always need to be balanced against likely benefits.” Semaglutide under the brand name Wegovy has been prescribed for weight loss on the NHS since 2023. A spokesperson for Novo Nordisk, the maker of Ozempic and Wegovy, said: “Patient safety is a top priority for Novo Nordisk and we take all reports about adverse events from use of our medicines very seriously. “Non-arteritic anterior ischemic optic neuropathy is not listed as a known adverse drug reaction in the summary of product characteristics (SmPC) for the marketed formulations of semaglutide (Ozempic and Rybelsus for type 2 diabetes and Wegovy for weight management) as per the approved labels.”