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Popular weight-loss jabs have been linked to an eye condition that can cause blindness.
People with diabetes prescribed semaglutide (brand names Wegovy and Ozempic) were more than four times more likely to be diagnosed with a condition called non-arteritic anterior ischemic optic neuropathy (NAION), according to a new study.
Meanwhile, people who were overweight or obese prescribed the drugs were more than seven times as likely to develop the condition as those on other weight-loss medicines.
NAION, which is uncommon, occurs from a lack of sufficient blood flow to the optic nerve.
People typically suffer sudden vision loss in one eye, without any pain, and patients often notice the issue on waking up.
There are no current treatments for NAION and vision often does not improve.
The new study, published in JAMA Ophthalmology, was led by Joseph Rizzo, a professor of ophthalmology at Harvard Medical School in the US.
He said: “The use of these drugs has exploded throughout industrialised countries and they have provided very significant benefits in many ways, but future discussions between a patient and their physician should include NAION as a potential risk.
“It is important to appreciate, however, that the increased risk relates to a disorder that is relatively uncommon.”
NAION is thought to affect 10 out of 100,000 people in the general population.
Prof Rizzo said the visual loss caused by NAION was painless and could progress over many days before stabilising.
He and colleagues decided to investigate a potential link between semaglutide and NAION last summer after three patients in his practice were diagnosed with vision loss caused by NAION in one week.
All the patients were taking semaglutide.
To investigate possible links, researchers examined data from more than 16,000 patients from Mass Eye and Ear (a Harvard teaching hospital) treated over a six-year period.
They compared patients who had received prescriptions for semaglutide with those taking other diabetes or weight-loss drugs.
Among 16,827 patients, 710 had type 2 diabetes, with 194 prescribed semaglutide.
Some 979 patients were overweight or obese, with 361 prescribed semaglutide.
In people with type 2 diabetes, 17 NAION events occurred in patients prescribed semaglutide compared to six on other diabetes drugs.
Over three years, 8.9% people on semaglutide had NAION compared to 1.8% on the other drugs, the researchers found.
Meanwhile, in patients who were overweight or obese, 20 NAION events occurred in people prescribed semaglutide, compared to three on other drugs.
Over three years, 6.7% people on semaglutide had NAION compared to 0.8% on other drugs.
The researchers said further, larger studies were needed, adding that Mass Eye and Ear saw an unusually high number of people with rare eye diseases.
They added that the number of NAION cases seen over the six-year study period was relatively small.
Prof Rizzo 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.”
Novo Nordisk, which makes Wegovy and Ozempic, has been contacted for comment.
Graham McGeown, honorary professor of physiology at Queen’s University Belfast, said the authors had acknowledged there were limitations to the study.
But he 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.”
