People who use Ozempic for weight loss presumably look forward to seeing their brand new selves in the mirror.

What they don’t expect is for the drug to send them blind – a possibility suggested in new research.

US investigators found that patients prescribed semaglutide – the active agent of Ozempic or Wegovy – for diabetes or weight loss “had a higher risk of having a potentially blinding eye condition called NAION than similar patients who had not been prescribed these drugs”.

Mass Eye and Ear (Massachusetts General Hospital), the world’s largest vision and hearing research centre, stated: The study found people with diabetes who were prescribed semaglutide “were more than four times more likely to be diagnosed with NAION”.

Those who were “prescribed this drug and were overweight or had obesity were more than seven times more likely to get the diagnosis”.

Dr Joseph Rizzo, is director of the Neuro-Ophthalmology Service at Mass Eye and Ear. Rizzo led the study and is the corresponding author.

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.”

However, he said it was “important to appreciate, however, that the increased risk relates to a disorder that is relatively uncommon”.

What is NAION?

NAION is the acronym for Non-arteritic Anterior Ischemic Optic Neuropathy, a form of blindness.

According to Mass Eye and Ear, NAION is relatively rare, occurring in up to 10 out of 100,000 people in the general population. However, it is the second-leading cause of optic nerve blindness, second only to glaucoma.

And it’s the most common cause of sudden optic nerve blindness.

NAION is “thought to be caused by reduced blood flow to the optic nerve head, with the consequence of permanent visual loss in one eye”.

According to Rizzo, the visual loss caused by NAION is painless. It may progress over many days before stabilising. And there is relatively little potential for improvement. There are currently no effective treatments for NAION.

How was this discovery made?

In 2023, Rizzo and colleagues noticed that three patients in their practice had been diagnosed with NAION in just one week.

All had suffered vision loss, and all were taking semaglutide.

This led Mass researchers to run what’s known as a “backward-looking analysis” of their patient population “to see if they could identify a link between this disease and these drugs”.

This involved analysing the records of more than 17,000 patients treated over the six years since Ozempic was released.

They divided the patients into two groups: Those who were diagnosed with diabetes or those who were overweight/obese.

The researchers looked at who had received prescriptions for semaglutide and who had taken other diabetes or weight loss drugs. When they analysed the rate of NAION diagnoses in the groups, the significant risk increases were revealed.

There are several limitations to the study.

Importantly, the study does not prove causality. The researchers do not state why there was a difference reported in diabetic and overweight groups.

“Our findings should be viewed as being significant but tentative,” said Rizzo.

He said future studies were needed.

“This is information we did not have before.”

It should be included in discussions between patients and their doctors, he said. Especially if patients have other optic nerve problems, or there is pre-existing significant visual loss from other causes.

Drug-maker critical of study

Novo Nordisk, the makers of Ozempic and Wegovy, stated the study lacked sufficient data to establish an association between semaglutide and NAION.

The company said the study’s design was limited. And it wasn’t conducted as a randomised controlled trial.

It said NAION was “not an adverse drug reaction” for publicly available forms of the drug.