Ozempic linked to risk of rare irreversible vision loss after large-scale trial

The findings, published on December 11 on medRxiv, support earlier research from Harvard University released this year.

The study analysed records of more than 44,000 Ozempic patients in Denmark and over 16,000 in Norway, tracking new users from 2018 onwards.

Researchers identified 32 cases of NAION across the entire group.

The overall occurrence rate was very low, with just 1.4 additional cases per 10,000 patients compared to those taking alternative diabetes medications.

The research team compared users of semaglutide, Ozempic's active ingredient, with patients taking older SGLT-2 class drugs.

Data collection continued until June 2024 in Denmark and May 2022 in Norway.

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NAION occurs when a loss of blood flow damages the optic nerve, and is most prevalent in people over 50.

The condition is irreversible, untreatable and potentially blinding, with doctors emphasising that patients should be informed of potential risks.

Diabetes, heart disease and sleep apnea can increase the likelihood of developing NAION.

According to the research team's calculations, a type 2 diabetes patient taking Ozempic for 20 years would have between 0.3 per cent and 0.5 per cent chance of developing the condition.

The researchers stressed the importance of weighing NAION risks against semaglutide's therapeutic benefits.

Novo Nordisk has stated that after evaluating the study and conducting its internal safety assessment, they believe the risk-benefit profile of the drug remains unchanged.

The company noted that very few cases of NAION were observed in their own trials, with no imbalance disadvantaging their medications.

The news had a significant impact on Novo Nordisk's market performance, with shares falling as much as 3.7 per cent in Copenhagen on Friday afternoon.

This marked the company's largest share price decline in approximately one month.

The findings follow a smaller study published by Harvard-affiliated Massachusetts Eye and Ear in July, which first suggested a link between Ozempic and NAION.

The Nordic study found a lower added risk compared to the Harvard research.

Researchers noted that the Harvard trial focused on patients who had been referred for neuro-ophthalmological assessment, suggesting they may have been in poorer health overall.

The study's findings regarding Wegovy were inconclusive, as the drug only became available in Denmark in 2022 and Norway in early 2023, resulting in insufficient patient data.